AQA GCSE COMBINED SCIENCE: SYNERGY

The topics listed below are for AQA GCSE Combined Science Synergy, with exam codes: AQA GCSE in Combined Science Synergy:

– Foundation 8465F – Higher 8465H The list provides everything you need for your AQA GCSECombined Science: Synergy exam, with topics broken in to the headings given by the exam board. More information is available here:

[https://www.aqa.org.uk/subjects/science/gcse/combined-science-synergy-8465/specification-at-a-glance]

For samples questions and papers, please click this link:

[https://www.aqa.org.uk/subjects/science/gcse/combined-science-trilogy-8464/assessment-resources?f.Resource+type%7C6=Question+papers]

Everything you need to know about your GCSE (9-1) Combined Science specifications can be found here.

Building Blocks

States of matter

A particle model

GCSE Science Subject Content

Recall and explain the main features of the particle model in terms of the states of matter and change of state, distinguishing between physical and chemical changes. (HT only) Explain the limitations of the
particle model in relation to changes of state when particles are represented by inelastic spheres.

Details of the Science Content

The three states of matter are solid, liquid and gas. Melting and freezing take place at the melting point, boiling and condensing take place at the boiling point.

The three states of matter can be represented by a simple model. In this model, particles are represented by small solid spheres. Particle theory can help to explain melting, boiling, freezing and condensing. (HT only) Limitations of the simple model include that there are no forces between the spheres, and that atoms, molecules and ions are not solid spheres.

Scientific, Practical and Mathematical Skills

WS 1.2
Recognise/draw simple diagrams to model the difference between substances in the solid, liquid and gas states.
WS 3.5
Predict the states of substances at different temperatures given appropriate data.
MS 1d
Relate the size and scale of atoms to objects in the physical world.

Density

GCSE Science Subject Content

Define density and explain the differences in density between the different states of matter in terms of the arrangements of the atoms or molecules.

Details of the Science Content

The density of a material is defined by the equation:
density = mass/volume
[ρ = m/V]
density, ρ, in kilograms per metre cubed, kg/m3
mass, m, in kilograms, kg
volume, V, in metres cubed, m3

Scientific, Practical and Mathematical Skills

MS 1a, 1b, 1c, 3c
Recall and apply this equation to changes where mass is conserved.
WS 3.3
Carry out and represent mathematical and statistical analysis.
WS 4.3, 4.5
Use and interconvert SI units in calculations.

Gas Pressure

GCSE Science Subject Content

Explain how the motion of the molecules in a gas is related both to its temperature and its pressure: hence explain the relation between the temperature of a gas and its pressure at constant volume
(qualitative only).

Details of the Science Content

The molecules of a gas are in constant random motion. The temperature of the gas is related to the average kinetic energy of the molecules. The higher the temperature, the greater the average kinetic energy and so the faster the average speed of the molecules. When the molecules collide with the wall of their container they exert a force on the wall. The total force exerted by all of the molecules inside the container on a unit area of the walls is the gas pressure. Changing the temperature of a gas, held at constant volume, changes the pressure exerted by the gas.

Heating and Changes of State

GCSE Science Subject Content

Describe how heating a system will change the energy stored within the system and raise its temperature or produce changes of state.
Describe how, when substances melt, freeze, evaporate, condense or sublimate, mass is conserved but that these physical changes differ from chemical changes because the material recovers its original properties if the change is reversed.

Define the term specific heat capacity and distinguish between it and the term specific latent heat.

Describe and calculate the changes in energy involved when a system is changed by heating (in terms of temperature change and specific heat capacity).

Details of the Science Content

Energy is stored inside a system by the particles (atoms and molecules) that make up the system. This is called internal energy.
The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance.

The increase in temperature of a system depends on the mass of the substance heated, the type of material and the energy input. The following equation, given on the Physics equations sheet, applies:

change in thermal energy = mass × specific heat capacity × temperature change

∆ E = m c ∆ θ

change in thermal energy, ∆E, in joules, J mass, m, in kilograms, kg

specific heat capacity, c, in joules per kilogram per degree Celsius, J/kg °C

temperature change, ∆θ, in degrees Celsius, °C

The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

The energy needed for a substance to change state is called latent heat. When a change of state occurs, the energy supplied changes the energy stored (internal energy) but not the temperature.

The specific latent heat of a substance is the amount of energy required to change the state of one kilogram of the substance with no change in temperature.

The following equation, given on the Physics equations sheet, applies:

energy f or a change o f state = mass × specific latent heat

E = m L energy, E, in joules ,

J mass, m, in kilograms, kg

specific latent heat, L, in joules per kilogram, J/kg

Specific latent heat of fusion – change of state from solid to liquid.

Specific latent heat of vaporisation – change of state from liquid to vapour.

Scientific, Practical and Mathematical Skills

This topic links with Structure and bonding.
(page 98)

WS 3.3
Carry out and represent mathematical and statistical analysis.

WS 3.5,

MS 4a
Interpret heating and cooling graphs that include changes of state.

WS 4.3, 4.5,

MS 1a,3c, 3d
Apply this equation, which is given on the Physics equations sheet, to calculate energy changes when
a material is heated or cooled.

WS 3.3
Carry out and represent mathematical and statistical analysis.

Meanings of Purity

GCSE Science Subject Content

Explain what is meant by the purity of a substance, distinguishing between the scientific and everyday use of the term ‘pure’.

Details of the Science Content

In chemistry, a pure substance is a single element or compound, not mixed with any other substance.
Pure elements and compounds melt and boil at specific temperatures. Melting point and boiling point data can be used to distinguish pure substances from mixtures.
In everyday language, a pure substance can mean a substance that has had nothing added to it, so it is unadulterated and in its natural state.

Scientific, Practical and Mathematical Skills

WS 3.5
Use melting point data to distinguish pure from impure substances.

Atomic Structure

Scientific Models of the Atom

GCSE Science Subject Content

Describe how and why the atomic model has changed over time.

Details of the Science Content

Stages in the development of atomic models:

• Dalton atoms (1804) – spherical atoms that cannot be split up to explain the properties of gases and the formulae of compounds

• Plum pudding model (1897) – it was found that the mass of electrons, which had recently been discovered, was very much less than the mass of atoms so they must be sub-atomic particles

• the nuclear atom (1911) – an experiment which showed that most of the alpha particles directed at thin gold foil passed through but a few bounced back, suggesting the positive charge was concentrated at the centre of each gold atom

• discovery of neutrons in the nucleus (1932) – explained why the mass of atoms was greater than could be accounted for by the mass of the protons.

Students are not required to recall dates or the names of scientists.

Scientific, Practical and Mathematical Skills

WS 1.1
Explain, with examples, why new data from experiments or observations led to changes in atomic models.
Decide whether or not given data supports a particular theory.

The Size of Atoms

GCSE Science Subject Content

Recall the typical size (order of magnitude) of atoms and small molecules.

Details of the Science Content

Atoms are very small, having a radius of about 0.1 nm (1 x 10^-10 m).

The radius of a small molecule such as methane, CH4, is about 0.5 nm (5 x 10^-10 m).

Scientific, Practical and Mathematical Skills

MS 1b
Interpret expressions in standard form.
WS 4.4
Use SI units and the prefix nano.
MS 1d
Estimate the size of atoms based on scale diagrams.

Sub-Atomic Particles

GCSE Science Subject Content

Describe the atom as a positively charged nucleus surrounded by negatively charged electrons, with the nuclear radius much smaller than that of the atom and with almost all of the mass in the nucleus.
Recall that atomic nuclei are composed of both protons and neutrons, that the nucleus of each element has a characteristic positive charge, but that elements can differ in nuclear mass by having different numbers of neutrons. Recall relative charges and approximate relative masses of protons, neutrons and electrons.

Details of the Science Content

The radius of a nucleus is less than 1/10 000 of that of the atom (about 1 x 10^-14 m).
The relative masses and charges of protons, neutrons and electrons are:

The number of protons in an atom of an element is its atomic number. All atoms of a particular element have the same number of protons. Atoms of different elements have different numbers of protons.
In an atom, the number of electrons is equal to the number of protons in the nucleus. Atoms have no overall electrical charge.

Scientific, Practical and Mathematical Skills

WS 1.2
Interpret and draw diagrams to represent atoms.

Isotopes

GCSE Science Subject Content

Relate differences between isotopes to differences in conventional representations of their identities, charges and masses.

Details of the Science Content

The sum of the protons and neutrons in an atom is its mass number.
Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element.
Atoms can be represented as shown in this example:

²³ Na ₁₁

Atomic Number 11, Mass Number 23

Scientific, Practical and Mathematical Skills

WS 1.2
Work out numbers of protons, neutrons and electrons in atoms and ions, given atomic number and mass number of isotopes.

Electrons in Atoms

GCSE Science Subject Content

Recall that in each atom its electrons are arranged at different distances from the
nucleus.

Details of the Science Content

The electrons in an atom occupy the lowest available energy levels (innermost available shells closest to the nucleus). The electronic structure of an atom can be represented by numbers or by a diagram. For example, the electronic structure of sodium is 2,8,1 or showing two electrons in the lowest energy level, eight in the second energy level and one in the third energy level.

Scientific, Practical and Mathematical Skills

This topic links with Atomic number and the periodic table (page 87).

Electron Microscopy

GCSE Science Subject Content

.Explain how electron microscopy has increased our understanding of subcellular structures.

Details of the Science Content

An electron microscope has a much higher resolving power than a light microscope. This means that it can be used to study cells in much finer detail. An electron microscope can magnify up to a million times (× 1000 000) or more, which is much more than a light microscope which has a useful magnification of only about a thousand times (× 1000).
magnification = size of image/size of real object

Scientific, Practical and Mathematical Skills

MS 2a, 2h

Demonstrate understanding of number, size and scale and the quantitative relationship between units.

WS 4.5

Interconvert units.

MS 1a,1b, 1c, 2h

Carry out calculations involving magnification, real size and image size including numbers written in standard form.

WS 3.3

Carry out and represent mathematical and statistical analysis.

WS 4.6

Use an appropriate number of significant figures.

WS4.4

Use prefixes centi, milli, micro and nano.

MS 1d, 2h

Make order of magnitude calculations.

MS 1d

Use estimations and explain when they should be used.

Cell Structures

GCSE Science Subject Content

Explain how the main sub-cellular structures of eukaryotic cells (plants and animals) and prokaryotic cells are related to their functions, including the nucleus/genetic material, plasmids, mitochondria,
chloroplasts and cell membranes.

Details of the Science Content

Plant and animal cells (eukaryotic cells) have a cell membrane, cytoplasm and a nucleus containing the genetic material. Bacterial cells (prokaryotic cells) are much smaller in comparison. They have cytoplasm and a cell membrane surrounded by a cell wall. The genetic material is not enclosed in a nucleus. It is a single DNA loop and may have one or more small rings of DNA called plasmids.

Most animal cells have the following parts:

• a nucleus

• cytoplasm

• a cell membrane

• mitochondria

• ribosomes.

Most human cells are like most other animal cells. In addition to the parts found in animal cells, plant cells often have:

• chloroplasts

• a permanent vacuole filled with cell sap.

Plant and algal cells also have a cell wall made of cellulose, which strengthens the cell.

Transport Into and Out of Cells

GCSE Science Subject Content

Explain how substances are transported into and out of cells through diffusion, osmosis and active transport.

Details of the Science Content

Some substances move across cell membranes via diffusion. Diffusion is a spreading out and mixing process. Particles move from a region where they are in higher concentration to a region where their
concentration is lower. Factors that affect the rate of diffusion across a membrane are:

• the difference in concentration

• the temperature

• the surface area of the membrane.

Water may move across cell membranes by osmosis. Cell membranes are partially permeable: they allow small molecules such as water through but not larger molecules. During osmosis water diffuses from where it is more concentrated (because the solute concentration is lower), through a partially permeable membrane to where water is less concentrated (because the solute concentration is higher). Some substances move across cell membranes via active transport. Active transport involves the movement of a dissolved substance from a region where it is less concentrated to a region where it is more concentrated. This requires energy from respiration.
Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil. It also allows sugar molecules to be absorbed from lower concentrations in the gut into the blood with a higher sugar concentration.

Scientific, Practical and Mathematical Skills

MS 4a, 4b, 4c, 4d

Plot, draw and interpret appropriate graphs.

WS 3.4

Represent the distribution of results and make estimations of uncertainty.

MS 1c

Calculate percentage gain and loss of mass.

WS 3.3

Carry out and represent mathematical and statistical analysis.

Mitosis and the Cell Cycle

GCSE Science Subject Content

Describe the process of mitosis in growth, including the cell cycle.

Details of the Science Content

The nucleus of body cells contains chromosomes. In body cells the chromosomes are normally found in pairs. There are 46 chromosomes in human body cells. DNA is in the chromosomes and each chromosome carries a large number of genes.
Cells divide so that organisms can grow during the development of multicellular organisms,
and repair damaged tissues. Dividing cells go through a series of stages called the cell cycle. During the cell cycle the genetic material doubles and then divides to give two new cells that are genetically identical to each other and to the original cell.
Knowledge of the stages of the cell cycle and mitosis is not required. Before a cell can divide it must grow, and make copies of all the organelles such as mitochondria and ribosomes. It must also
replicate the chromosomes in the nucleus.
Then it can divide by mitosis. During mitosis, the two complete sets of chromosomes are pulled to opposite sides of the cell. Two new nuclei form. Then the cell splits into two.

Meiosis

GCSE Science Subject Content

Explain the role of meiotic cell division in halving the chromosome number to form gametes.

Details of the Science Content

Cells in reproductive organs divide by meiosis to form gametes (egg and sperm cells). Knowledge of the stages of meiosis is not required.

When a cell divides to form gametes:

• copies of the genetic information are made

• the cell divides twice to form four gametes, each with a single set of chromosomes

• all gametes are genetically different from each other.

Gametes join at fertilisation to make a new cell with the normal number of chromosomes. The new cell divides by mitosis to grow.

Cell Differentiation

GCSE Science Subject Content

Describe the function of stem cells in embryonic and adult animals. Explain the importance
of cell differentiation.

Details of the Science Content

At first the cells in an embryo can grow and divide to form any type of cell. They are stem cells.
As an embryo develops most of the cells differentiate and become specialised. Specialised cells carry out a particular function. Differentiation is essential to produce a variety of cells with different functions in multicellular organisms (animals and plants).
Cells that have become specialised cannot later change into different kinds of cells. However, there are some stem cells in most adult tissues that are ready to start dividing to replace old cells or to repair damage in the tissues where they are found..

Scientific, Practical and Mathematical Skills

This section links with Stem cells (page 66).

Waves

Transverse and Longitudinal Waves

GCSE Science Subject Content

Describe the difference between transverse and longitudinal waves.
Describe how ripples on water surfaces are examples of transverse waves whilst sound waves in air are longitudinal waves, and how the speed of each may be measured.
Describe evidence that in both cases it is the wave and not the water or air itself that travels.

Details of the Science Content

In a transverse wave the oscillations are perpendicular to the direction of energy transfer. The ripples on a water surface are an example of a transverse wave.
In a longitudinal wave the oscillations are parallel to the direction of energy transfer. Longitudinal waves show areas of compression and rarefaction. Sound waves travelling through air are longitudinal.

Scientific, Practical and Mathematical Skills

WS 2.3

Describe one method to measure the speed of sound waves in air.

WS 2.2, 2.3

Describe one method to measure the speed of ripples on a water surface.

WS 3.5

Interpret given data from experiments to measure the speed of sound or water waves..

A Wave Equation

GCSE Science Subject Content

Describe wave motion in terms of amplitude, wavelength, frequency, and period; define wavelength and frequency and describe and apply the relationship between these and the wave velocity.

Details of the Science Content

Waves are described by their amplitude, wavelength, frequency and period.

The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed position.
The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave.
The frequency of a wave is the number of waves passing a point each second.
The wave speed is the speed at which the energy is transferred (or the wave moves) through the medium.
All waves obey the wave equation:
wave speed = frequency × wavelength
v = f λ
wave speed, v, in metres per second, m/s frequency, f, in hertz, Hz wavelength, λ, in metres, m
Students should be able to apply the relationship:
period = 1/frequency
T = 1/f
period, T, in seconds, s frequency, f, in hertz, Hz

Scientific, Practical and Mathematical Skills

WS 4.6,

MS 1b, 2a
Calculate with numbers written in standard form and give answers to an appropriate number of significant figures.
MS 1c, 3b, 3c
Recall and apply the wave equation.
MS1a, 1c, 3b, 3c
Apply the equation for relationship between period and frequency, which is given on the Physics equations sheet.
WS 3.3
Carry out and represent mathematical and statistical analysis.

Electromagnetic Waves

GCSE Science Subject Content

Recall that electromagnetic waves are transverse, are transmitted through space where all have the same velocity, and explain, with examples, that they transfer energy from source to absorber.
Recall that light is an electromagnetic wave. Describe the main groupings of the spectrum – radio, microwave, infrared, visible (red to violet), ultraviolet, X-rays and gamma rays, that these range from long to short wavelengths and from low to high frequencies, and that our eyes can only detect a limited range.
Give examples of some practical uses of electromagnetic waves in the radio, microwave, infrared, visible, ultraviolet, Xray and gamma ray regions

Details of the Science Content

Electromagnetic waves form a continuous spectrum. Examples of uses of electromagnetic waves include:

• radio waves – television, radio and radio telescopes

• microwaves – satellite communications, cooking food

• infrared – electrical heaters, cooking food, infrared cameras

• visible light – fibre optic communications

• ultraviolet – fluorescent lamps, sun tanning

• X-rays – medical imaging and treatments

• gamma rays – sterilising surgical instruments, treatment of cancer.

Scientific, Practical and Mathematical Skills

WS 1.2

Show that the uses of electromagnetic waves illustrate the transfer of energy from source to absorber.

MS 1a, 1c, 3c

Recall and apply the relationship between frequency and wavelength across the electromagnetic spectrum.

Radio Waves (HT only)

GCSE Science Subject Content

Recall that radio waves can be produced by, or can themselves induce, oscillations in electrical circuits

Details of the Science Content

When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself, so radio waves can themselves induce oscillations in an electrical circuit.

Reflection and Refraction of Electromagnetic Waves (HT only)

GCSE Science Subject Content

Recall that different substances may refract, or reflect these waves; explain how some effects are related to differences in the velocity of the waves in different substances.

Details of the Science Content

Shiny surfaces act as mirrors when they reflect waves. Rough surfaces scatter waves in all directions.

Electromagnetic waves change speed when they travel between different substances such as from air to glass or water. As a result they change direction. This is refraction.

Scientific, Practical and Mathematical Skills

WS 1.2

Construct ray diagrams to illustrate the refraction of a wave at the boundary between two different media.

Use wavefront diagrams to explain refraction in terms of the change of wave speed.

Transport Over Larger Distances

Respiration

GCSE Science Subject Content

Describe cellular respiration as an exothermic reaction which is continuously occurring in all living cells.

Compare the processes of aerobic and anaerobic respiration.

Details of the Science Content

Respiration in cells can take place aerobically (using oxygen) or anaerobically (without oxygen).
Aerobic respiration is an exothermic reaction that can be represented by word and symbol equations.
glucose + oxygen → carbon dioxide + water

An exothermic reaction is one that transfers energy to its surroundings.
Organisms need energy for:

• chemical reactions to build larger molecules

• movement

• keeping warm.

Anaerobic respiration in muscles is also exothermic but it gives out less energy. It is represented by the word equation:
glucose → lactic acid
Because the oxidation of glucose is incomplete in anaerobic respiration much less energy is given out than in aerobic respiration. If insufficient oxygen is supplied, anaerobic respiration takes place in muscles. The incomplete oxidation of glucose causes a buildup of lactic acid and creates an oxygen debt.
Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.

Scientific, Practical and Mathematical Skills

WS 1.2 (HT only)

Write a balanced symbol equation for respiration, given the formula of glucose.

Exchange Surfaces

GCSE Science Subject Content

Explain the need for exchange surfaces and a transport system in multicellular organisms in terms of surface area:volume ratio.

Details of the Science Content

A single-celled organism has a relatively large surface area:volume ratio. The tissues of a multicellular organism consist of cells with a similar structure and function.
Organs, such as the heart and lungs, are made of tissues. One organ may consist of several tissues. Organ systems, such as the circulatory system, are groups of organs that perform a particular function.
In multicellular organisms many organ systems are specialised for exchanging materials. The effectiveness of an exchange surface is increased by:

• having a large surface area

• a membrane that is thin, to provide a short diffusion path

• (in animals) having an efficient blood supply

• (in animals, for gaseous exchange) being ventilated.

Scientific, Practical and Mathematical Skills

MS 1c

Calculate and compare surface area:volume ratios.

The Human Circulatory System

GCSE Science Subject Content

Describe the human circulatory system, including the relationship with the gaseous exchange system, and explain how the structure of the heart and the blood vessels are adapted to their functions. Describe some of the substances transported into and out of a range of organisms in terms of the requirements of those organisms, to include oxygen, carbon dioxide and dissolved food molecules.

Details of the Science Content

The heart is a muscular organ that pumps blood around the body in a dual circulatory system.
The right ventricle pumps blood to the lungs, where gas exchange takes place. The left ventricle pumps blood around the rest of the body.
Valves prevent the blood from flowing back from the ventricles to the atria. Knowledge of the names of the heart valves is not required. Blood vessels associated with the heart include the aorta, vena cava, pulmonary artery, pulmonary vein and coronary arteries.
Gas exchange takes place in the lungs. Important features of the lungs are the trachea, bronchi, alveoli and the capillary network surrounding the alveoli. The alveoli have the specialised surfaces for gas exchange between air and the blood.
The natural resting heart rate is controlled by a group of cells that act as a pacemaker, located in the right atrium. Artificial pacemakers are electrical devices used to correct irregularities in the heart rate.

The body contains three different types of blood vessel:

• arteries

• veins

• capillaries.

Scientific, Practical and Mathematical Skills

MS 1a, 1c

Use simple compound measures such as rate.

MS 1a, 1c

Carry out rate calculations.

Blood Cells

GCSE Science Subject Content

Explain how red blood cells, white blood cells, platelets and plasma are adapted to their functions in the blood.

Details of the Science Content

Blood is a tissue consisting of plasma, in which are suspended:

• red blood cells

• white blood cells

• platelets.

Scientific, Practical and Mathematical Skills

WS 3.5

Identify different types of blood cells in a photograph or diagram.

The Human Digestive System

GCSE Science Subject Content

Explain the importance of sugars, amino acids, fatty acids and glycerol in the synthesis and
breakdown of carbohydrates, lipids and proteins. Describe some of the substances transported into and out of a range of organisms in terms of the requirements of those organisms, to include dissolved food molecules and urea.

Details of the Science Content

The digestive system uses enzymes to break down large molecules in food into small soluble molecules that can be absorbed into the blood through the walls of the gut. The blood carries
the small molecules to the cells of the body where they can be used for respiration or to make the new large molecules that the cells need as reserves of energy or for growth and repair.
Starch is a carbohydrate. Its molecules consist of a long chain of glucose molecules. Digestion by carbohydrase enzymes breaks down insoluble starch to water-soluble glucose. Cells use glucose during respiration.
Lipids are fats and oils. Digestion by lipase enzymes breaks down lipids to glycerol and fatty acids. Cells reform fats from the fatty acids and glycerol molecules. Fats are stored as a source of energy because cells can break them down and use them in respiration.
Proteins are long-chain molecules made up of many amino acids linked together. Digestion by protease enzymes breaks down proteins to amino acids. Cells use amino acids to make new proteins.
The liver breaks down unwanted amino acids to urea, which is then carried by the blood to the kidneys. The kidneys excrete urea in solution as urine.

The Human Nervous System

GCSE Science Subject Content

Explain how the structure of the nervous system (including the central nervous system, sensory and motor neurones and sensory receptors) is adapted to its functions.

Explain how the structure of a reflex arc is related to its function.

Explain methods of measuring human reaction times and recall typical results.

Details of the Science Content

The nervous system enables humans to react to their surroundings and to coordinate their behaviour.
Information from receptors passes along cells (neurones) as impulses to the central nervous system, or CNS (the brain or the spinal cord).
The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.
stimulus → receptor → coordinator → effector → response

Reflex actions are automatic and rapid; they do not involve the conscious part of the brain.
An example of a simple reflex action is the pain withdrawal reflex. This can be explained in terms of a reflex arc.

Sensory neurones carry impulses from receptors to the spinal cord and brain. Relay neurones carry impulses within the CNS. Motor neurones carry impulses from the CNS to effectors.

Where two neurones meet, there is a tiny gap called a synapse. Impulses cross this gap using chemicals

Reaction times vary from person to person.
Typical values range from 0.3s to 0.9s.

Scientific, Practical and Mathematical Skills

This topic links with Stopping distances (page 115).

The Human Endocrine System

GCSE Science Subject Content

Describe the principles of hormonal coordination and control by the human endocrine system

(HT only) Explain the roles of thyroxine and adrenaline in the body including thyroxine as an example of a negative feedback system.

Details of the Science Content

The endocrine system is composed of glands that secrete hormones directly into the bloodstream. Hormones are large molecules. The blood carries the hormone to a target organ where it produces an effect. Compared to the nervous system the effects are slower but act for longer.
The pituitary gland in the brain is a ‘master gland’. It secretes several hormones that act on other glands to stimulate other hormones to be released.

(HT only) Adrenaline is produced by the adrenal gland. It boosts the delivery of oxygen and glucose to the brain and muscles and prepares the body for ‘flight or fight’.
(HT only) Thyroxine from the thyroid gland stimulates the basal metabolic rate. It plays an important role in growth and development.
(HT only) The control of thyroxine levels involves negative feedback. Negative feedback tends to stabilise a system. Any change in the system leads to a response that tends to reverse the change.

Scientific, Practical and Mathematical Skills

WS1.2, MS 2c

(HT only) Interpret and explain simple diagrams of negative feedback control.

Plants and Photosynthesis

Meristem Tissue

GCSE Science Subject Content

Describe the function of meristems in plants.

Details of the Science Content

Meristem tissue contains the cells in a plant that divide as the plant grows. This type of tissue is found at the growing tips of shoots and roots. The cells differentiate into different types of plant cells depending on where they are in the plant.

Scientific, Practical and Mathematical Skills

WS 1.4

Describe and explain the use of stem cells from meristems to produce clones of plants quickly and economically.

Plant Structures

GCSE Science Subject Content

Describe some of the substances transported into and out of a range of organisms, in terms of the requirements of those organisms, to include oxygen, carbon dioxide, water and mineral ions.

Details of the Science Content

Plants, like other multicellular organisms, need specialised structures for transporting and exchanging materials. The roots, stem and leaves form a plant organ system for transport of substances around the plant. Plants take in carbon dioxide from the atmosphere for photosynthesis and oxygen for respiration. Plants take in water from the soil with dissolved ions including nitrate ions to make proteins and magnesium ions to make chlorophyll.

Transpiration

GCSE Science Subject Content

Explain the need for exchange surfaces and a transport system in multicellular organisms. Explain how water and mineral ions are taken up by plants, relating the structure of the root hair cells to their function. Explain how the structure of xylem is adapted to its functions in the plant. Describe the process of transpiration including the structure and function of the stomata.

Explain the effect of a variety of environmental factors on the rate of water uptake by a plant, to include light intensity, air movement and temperature.

Details of the Science Content

Water is drawn into the roots of plants from the soil. Water moves into the root hairs by osmosis. Mineral ions move from the soil into the root hairs by active transport. Water flows from the roots through xylem in its stems to its leaves. Xylem tissue is composed of hollow tubes strengthened by lignin adapted for the transport of water in the transpiration stream from the roots to the leaves. Water evaporates in the leaves and the water vapour escapes through tiny holes in the surface of leaves called stomata. The stomata can open or close as conditions change because the guard cells can gain or lose water by osmosis.

The rate of transpiration varies with:

• light intensity, which affects the opening of stomata
• air movements, which affect the concentration of water vapour in the air around leaves
• temperature, which affects the rate at which water evaporates.

Scientific, Practical and Mathematical Skills

MS 1a, 1c

Understand and use simple compound measures such as the rate of a reaction.

MS 4a

Translate information between graphical and numerical form.

MS 4a, 4c

Plot and draw appropriate graphs, selecting appropriate scales for axes.

WS 3.3
Carry out and represent mathematical and statistical analysis.

MS 2c, 4a
Extract and interpret information from graphs, charts and tables

Chlorophyll and Other Plant Pigments

GCSE Science Subject Content

Recall that chromatography involves a stationary and a mobile phase and that separation depends on the distribution between the phases. Interpret chromatograms, including measuring Rf values.
Suggest chromatographic methods for distinguishing pure from impure substances

Details of the Science Content

The chlorophyll and other pigments in plant leaves can be separated and identified by chromatography. Chromatography can be used to separate mixtures and can give information to
help identify substances. The ratio of the distance moved by a compound (centre of spot from origin) to the distance moved by the solvent can be expressed as its Rf value:

Rf = distance moved by substance/distance moved by solvent

Different compounds have different Rf values in different solvents, which can be used to help identify the compounds. The compounds in a mixture may separate into different spots depending on the solvent, but a pure compound produces a single spot in all solvents.

Scientific, Practical and Mathematical Skills

MS 1a

Recognise and use expressions in decimal form.

MS 1c

Use ratios and percentages.

WS 3.3

Carry out and represent mathematical and statistical analysis.

MS 1d

Make estimates of the results of simple calculations.

WS 4.6, MS 2a

Use an appropriate number of significant figures.

MS 4a
Extract and interpret information from charts and tables. Translate information between graphical and
numeric form when calculating Rf values.

Photosynthesis

GCSE Science Subject Content

Describe the process of photosynthesis and describe photosynthesis as an endothermic reaction.

Details of the Science Content

Photosynthesis takes place in the chloroplasts in the cells of the leaves of plants. The chloroplasts contain the chlorophyll, which absorbs sunlight.
Photosynthesis is an endothermic reaction that can be represented by word and symbol equations. carbon dioxide + water → glucose + oxygen

Energy is transferred to the plant cells by light. The glucose produced in photosynthesis may be:

• used for respiration
• converted into insoluble starch for storage
• used to produce fat or oil for storage
• used to produce cellulose, which strengthens the cell wall
• used to produce amino acids for protein synthesis.

To produce proteins, plants also use nitrate ions that are absorbed in solution from the soil.

Scientific, Practical and Mathematical Skills

WS 1.2 (HT only)

Write a balanced symbol equation for photosynthesis given the formula of glucose.

Factors Affecting the Rate of Photosynthesis

GCSE Science Subject Content

Explain the effect of temperature, light intensity and carbon dioxide concentration on the rate of
photosynthesis.

(HT only) Explain the interaction of these factors in limiting the rate of photosynthesis.

Details of the Science Content

The rate of photosynthesis depends on:

• the energy available from light

• the concentration of carbon dioxide in the air

• the temperature.

(HT only) The rate of photosynthesis may be limited by:

• low temperature

• shortage of carbon dioxide
• shortage of light.

(HT only) Increasing any one of the factors speeds up photosynthesis until the rate is limited by the factor which is in shortest supply.

Scientific, Practical and Mathematical Skills

MS 1a, 1c Carry out rate calculations for photosynthesis.

WS 1.4 (HT only)

Use data to relate limiting factors to the cost effectiveness of adding heat, light or carbon dioxide to greenhouses.

MS 1a, 1c, 2c, 4a, 4c

Translate information between numerical and graphical forms and extract and interpret information from graphs, charts and tables.

WS 3.5 (HT only)

Understand and use inverse proportion – the inverse square law – and light intensity in the context of factors affecting photosynthesis.

Translocation

GCSE Science Subject Content

Describe the process of translocation. Explain how the structure of phloem is adapted to its functions
in the plant.

Details of the Science Content

Phloem tissue is composed of tubes of elongated living cells adapted for translocation of sugars from where they are produced by photosynthesis in the leaves to other parts of the plant for immediate use or storage. Cell sap containing sugars and other nutrients is able to move easily from one phloem cell to the next as the end walls have pores.

Plant Diseases

GCSE Science Subject Content

Explain how communicable diseases are spread in plants.

Explain how the spread of communicable diseases may be reduced or prevented in plants, to include a minimum of one plant disease.

Details of the Science Content

Tobacco mosaic virus is a widespread plant pathogen affecting many species of plants, including tomatoes. It gives a distinctive ‘mosaic’ pattern of discolouration on the leaves, which affects the growth of the plant due to lack of photosynthesis.
Rose black spot is a fungal disease where purple or black spots develop on leaves, which often turn yellow and drop early. It affects the growth of the plant as photosynthesis is reduced. The disease is spread by spores of he fungus that are produced in the black spots

Common control methods for tobacco mosaic virus include:

• removing and destroying infected plants

• washing hands and tools after handling infected plants

• crop rotation to avoid planting in soil that has been infected for at least two years.

Methods to control black spot include:

• not planting roses too close together – to allow the air to flow freely around them
• avoiding wetting the leaves when watering – wet leaves encourage the fungal disease
• cleaning up any infected leaves from the ground round the roses – to avoid spores spreading
• using a fungicide to prevent infection – spraying, especially in advance of warm, wet weather.

Scientific, Practical and Mathematical Skills

WS 1.4

Explain applications of science to prevent the spread of plant diseases.

Lifestyle and Health

Health and Disease

GCSE Science Subject Content

Describe the relationship between health and disease. Describe different types of diseases (including communicable and non-communicable diseases).

Details of the Science Content

Health can be defined as ‘a state of physical, mental and social well-being’ and not merely the absence of disease. Factors including diet, stress and life situations can affect both physical and mental health.
Diseases stop part of the body from working properly. This causes symptoms, which are experienced by the person affected by the disease.
Communicable (infectious) diseases are caused by microorganisms called pathogens. They may infect plants as well as animals and are spread by direct contact, by water or by air.
Non-communicable diseases, such as heart disease, cancer and diabetes, are the leading
cause of death in the world.

Risk Factors for Non-Communicable Diseases

GCSE Science Subject Content

Recall that many noncommunicable human diseases are caused by the interaction of a
number of factors. To include cardiovascular diseases, many forms of cancer, some lung and liver diseases and diseases influenced by nutrition, including Type 2 diabetes.
Explain the effect of lifestyle factors, including exercise, diet, alcohol and smoking, on the incidence of noncommunicable diseases at local, national and global levels.

Details of the Science Content

Risk factors are aspects of a person’s lifestyle, or substances present in a person’s body or environment, that have been shown to be linked to an increased rate of a disease. For some a causal mechanism has been proven.

Examples are:

• the effects of diet, smoking and exercise on cardiovascular disease

• obesity as a risk factor for Type 2 diabetes

• the effect of alcohol on liver and brain function

• the effect of smoking on lung disease and lung cancer

• the effects of smoking and alcohol on unborn babies

• carcinogens and ionising radiation as risk factors in cancer.

Scientific, Practical and Mathematical Skills

WS 1.5
Interpret data about risk factors, or about differences in the incidence of noncommunicable diseases in different parts of the world.
WS 1.4
Discuss the human and financial cost of these non-communicable diseases to an individual, a local
community, a nation or globally.
MS 4a
Translate information between graphical and numerical forms.
MS 2c, 4a
Extract and interpret information from charts, graphs and tables.
MS 2d
Understand the principles of sampling as applied to scientific data in terms of risk factors.
MS 2c
Construct and interpret frequency tables and diagrams, bar charts and histograms.
MS 2g
Use a scatter diagram to identify a correlation between two variables.

Treatments for Cardiovascular Disease

GCSE Science Subject Content

Evaluate some different treatments for cardiovascular disease.

Details of the Science Content

In coronary heart disease layers of fatty material build up inside the coronary arteries. This reduces the flow of blood through the coronary arteries. This can lead to a heart attack.
Statins are widely used to reduce blood cholesterol levels, which slows down the rate of fatty material deposit. Stents are used to keep the coronary arteries open.
In some people heart valves may become faulty, preventing the valve from opening fully, or the heart valve might develop a leak. Faulty heart valves can be replaced using biological or mechanical valves. In the case of heart failure, a donor heart, or heart and lungs, can be transplanted. Artificial
hearts are occasionally used to keep patients alive whilst waiting for a heart transplant, or to allow the heart to rest as an aid to recovery

Scientific, Practical and Mathematical Skills

WS 1.4

Evaluate given information about the advantages and disadvantages of treating cardiovascular diseases by drugs, mechanical devices or transplant.

WS 1.3

Evaluate methods of treatment bearing in mind the benefits and risks associated with the treatment.

Homeostasis

GCSE Science Subject Content

Explain the importance of maintaining a constant internal environment in response to internal and external change

Details of the Science Content

Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes. Homeostasis is important because it maintains optimal conditions for enzyme action and all cell functions.
Control of blood glucose concentration, control of body temperature and control of water levels in the human body are examples of homeostasis.
An organism maintains homeostasis by monitoring its internal conditions and responding appropriately when these conditions deviate from their optimal state.
These automatic control systems may involve nervous responses or chemical responses. Many of the processes are coordinated by hormones.

Insulin and diabetes

GCSE Science Subject Content

Explain how insulin controls blood sugar levels in the body. (HT only) Explain how glucagon interacts with insulin to control blood sugar levels in the body.

Compare Type 1 and Type 2 diabetes and explain how they can be treated.

Details of the Science Content

Blood glucose concentration is monitored and controlled by the pancreas.
If the blood glucose concentration is too high, the pancreas produces the hormone insulin, which causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage. (HT only) If the blood glucose concentration is too low, the pancreas produces glucagon, which causes glycogen to be converted into glucose and released into the blood.

Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections.

In Type 2 diabetes the body cells no longer respond to insulin produced by the pancreas. A carbohydrate controlled diet and an exercise regime are common treatments. Obesity is a risk factor for Type 2 diabetes.

Scientific, Practical and Mathematical Skills

MS 1a, 1c, 2c, 4a, 4c
Translate information between numerical and graphical forms and extract and interpret information from graphs, charts and tables.

Human Reproductive Hormones

GCSE Science Subject Content

Describe the roles of hormones in human reproduction, including the menstrual cycle.
(HT only) Explain the interactions of FSH, LH, oestrogen and progesterone in the control of the menstrual cycle.

Details of the Science Content

During puberty reproductive hormones cause secondary sex characteristics to develop. Oestrogen is the main female reproductive hormone produced in the ovary. At puberty eggs begin to mature and one is released approximately every 28 days. This is called ovulation. Testosterone is the main male reproductive hormone produced by the testes and it stimulates sperm production. Several hormones are involved in the menstrual cycle of a woman.

• Follicle-stimulating hormone (FSH) causes maturation of an egg in the ovary.

• Luteinising hormone (LH) stimulates the release of the egg.

• Oestrogen and progesterone are involved in maintaining the uterus lining.

Scientific, Practical and Mathematical Skills

MS 2c, 4a (HT only)

Extract and interpret data from graphs showing hormone levels during the menstrual cycle.

Contraception

GCSE Science Subject Content

Explain the use of hormones in contraception and evaluate hormonal and non-hormonal methods of contraception.

Details of the Science Content

Fertility can be controlled by a variety of hormonal and non-hormonal methods of contraception. These include:
• oral contraceptives that contain hormones
• injection, implant or skin patch of slow release progesterone
• barrier methods such as condoms and diaphragms
• intrauterine devices
• spermicidal agents
• abstaining from intercourse at times when an egg may be fertilised
• surgical methods of male and female sterilisation.

Scientific, Practical and Mathematical Skills

WS 1.4

Explain everyday and technological applications of science; evaluate associated personal, social, economic and environmental implications; and make decisions based on the evaluation of evidence and arguments.

Treatments for Infertility (HT only)

GCSE Science Subject Content

Explain the use of hormones in modern reproductive technologies to treat infertility.

Details of the Science Content

The uses of hormones in controlling fertility include:

• giving FSH and LH in a ‘fertility drug’ to a woman whose own level of FSH is too low

• In Vitro Fertilisation (IVF) treatment, which involves giving a mother FSH and LH to stimulate the maturation of several eggs.

Scientific, Practical and Mathematical Skills

WS 1.4

Evaluate, from the perspective of patients and doctors, the methods of treating fertility bearing in mind that although fertility treatment gives couples the chance to have a baby of their own it is very emotionally and physically stressful; the success rates are not high and it can lead to multiple births which are a risk to both the babies and the mother.

Absorption and Emission of Radiation

GCSE Science Subject Content

Recall that the arrangements of electrons in atoms may change with absorption or emission of electromagnetic radiation.

Details of the Science Content

When atoms gain energy by heating, from electricity, or by absorbing electromagnetic radiation, some electrons jump to higher energy levels. Electromagnetic radiation is given out when the electrons drop back to lower levels.
The frequency of the radiation depends on the size of the energy jump. Atoms of elements such as neon and sodium give out light in the visible region of the spectrum. Other atoms, such as mercury atoms, give out light in the ultraviolet region.

Scientific, Practical and Mathematical Skills

WS 1.2

Use of the energy level model of the atom.

Radioactive Decay

GCSE Science Subject Content

Recall that some nuclei are unstable and may emit alpha particles, beta particles, or neutrons, and
electromagnetic radiation as gamma rays; relate these emissions to possible changes in the mass or
the charge of the nucleus, or both.Use names and symbols of common nuclei and particles to write balanced equations that represent radioactive decay.

Details of the Science Content

The nuclear radiation emitted may be:

• an alpha particle (α) – this consists of two neutrons and two protons; it is identical to the nucleus of a helium atom

• a beta particle (β) – a high-speed electron ejected from the nucleus as a neutron turns into a proton

• a gamma ray (γ) – electromagnetic radiation from the nucleus

• a neutron (n).

Nuclear equations are used to represent radioactive decay.

In a nuclear equation an alpha particle may be represented by the symbol:

42He

and a beta particle by the symbol:

0-1e

The emission of the different types of ionising radiation may cause a change in the mass and/or the charge of the nucleus. For example, alpha decay causes the atomic number to decrease by two units and the mass number by four units:

Equation…….

There is no change in mass number during beta decay but the atomic number increases by one unit.

Equation……

Students are not required to recall these two examples. The emission of a gamma ray does not cause
the mass or the charge of the nucleus to change.

Scientific, Practical and Mathematical Skills

WS 1.2, MS 1b, 1c, 3c

Refer to a copy of the periodic table and use the names and symbols of common nuclei and particles to write balanced equations that show single alpha (α) and beta (β) decay. This includes balancing atomic numbers and mass numbers.

Half-Life

GCSE Science Subject Content

Explain the concept of half-life and how this is related to the random nature of radioactive decay.

Details of the Science Content

Radioactive decay is random, so it is not possible to predict which individual nucleus will decay next. But with a large enough number of nuclei it is possible to predict how many will decay in a certain amount of time.
The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in a sample to halve, or the average time it takes for the count rate from a sample containing a radioactive isotope to fall to half its initial level.
Count rate is the number of decays recorded each second by a detector (such as a Geiger– Müller tube).

Scientific, Practical and Mathematical Skills

WS 3.3

Carry out and represent mathematical and statistical analysis.

MS 4a

Determine the half-life of a radioactive isotope from given information.

MS 1c, 3d (HT only)

Calculate the net decline, expressed as a ratio, in a radioactive emission after a given number of half-lives.

Penetration Properties of Radiations

GCSE Science Subject Content

Recall the differences in the penetration properties of alpha particles, beta particles and gamma rays.

Details of the Science Content

Alpha particles are absorbed by just a few millimetres of air or by a thin sheet of paper. Beta particles can pass through air and paper but are completely absorbed by a sheet of metal just a few millimetres thick. Gamma rays pass through most materials easily but are absorbed by a thick sheet of lead or by several metres of concrete.

Contamination and Irradiation

GCSE Science Subject Content

Recall the differences between contamination and irradiation effects and compare the hazards associated with these two.

Details of the Science Content

Irradiation is the process of exposing an object to radiation from an outside source. Irradiation can be reduced by screening the source or moving the object away from it. The irradiated object does not become radioactive.
Radioactive contamination is the unwanted presence of a source of radiation inside, or on the surface of, other materials. It is often difficult to remove the contaminating source so that it continues to add to the radiation dose for as long as it emits radiation.

Ionising Radiations

GCSE Science Subject Content

Recall that changes in atoms and nuclei can also generate and absorb radiations over a wide frequency range.
Describe how ultraviolet waves, Xrays and gamma rays can have hazardous effects, notably on human bodily tissues.
Recall that atoms can become ions by loss of outer electrons.

Details of the Science Content

The hazardous effects of ultraviolet (UV) waves, X-rays, alpha, beta and gamma rays depend on the type of radiation and the size of the dose. Radiation dose (in Sieverts) is a measure of the risk of harm resulting from an exposure of the body to the radiation. 1 Sievert (Sv) = 1000 millisieverts (mSv). Ultraviolet waves, X-rays, alpha, beta and gamma rays are all examples of ionising radiation. They can turn atoms into ions and break up molecules. Ionising radiations can change DNA, causing mutation of genes that may lead to cancer. High-energy gamma rays can be used to destroy cancer cells.

Scientific, Practical and Mathematical Skills

WS 1.5

Interpret simple measures of risk showing the probability of harm from different types of radiation. Describe precautions that can be taken to reduce the risks from ionising radiation. Give examples to show that the perceived risk can be very different from the measured risk, especially if the cause of the risk is unfamiliar or invisible.

Cancer

GCSE Science Subject Content

Describe cancer as the result of changes in cells that lead to uncontrolled growth and division.

Details of the Science Content

Tumours form when cells start growing and dividing in an uncontrolled way. Some tumours are benign; they stay in the same place and stop growing before they get too large.
Cancer is caused by malignant tumours that are able to invade neighbouring tissues and spread to different parts of the body in the blood so that more tumours start to grow in other parts of the body.

Spread of Communicable Diseases

GCSE Science Subject Content

Explain how communicable diseases (caused by viruses, bacteria, protists and fungi) are spread in animals.

Details of the Science Content

Harmful microorganisms (pathogens) that cause disease can spread:

• through the air when people cough or sneeze

• through food that is contaminated with bacteria

• through drinking water that is contaminated with microorganisms

• through contact with other people, or surfaces that infected people have touched

• by animals that scratch, bite or draw blood.

Scientific, Practical and Mathematical Skills

WS 1.2

Apply the ideas in this section to the transmission of the common cold, flu, cholera, athlete’s foot and malaria.

Human Communicable Diseases

GCSE Science Subject Content

Describe a minimum of one common human infection, and sexually transmitted infections in humans, including HIV/AIDS.
Explain how the spread of communicable diseases may be reduced or prevented in animals. This should include a minimum of one common human infection, and sexually transmitted infections in humans including HIV/AIDS.

Details of the Science Content

Salmonella food poisoning is spread by bacteria ingested in food, or on food prepared in unhygienic conditions. Fever, abdominal cramps, vomiting and diarrhoea are caused by the bacteria and the toxins they secrete.
Salmonella bacteria are killed by cooking and pasteurisation. In the UK, poultry are vaccinated against Salmonella to control the spread.
Measles is a viral disease showing symptoms of fever and a red skin rash. Measles is a serious illness that can be fatal if complications arise. For this reason most young children are vaccinated against measles. The measles virus is spread by inhalation of droplets from sneezes and coughs.
Gonorrhoea is a sexually transmitted disease (STD) with symptoms of a thick yellow or green discharge from the vagina or penis and pain on urinating. It is caused by a bacterium and was
easily treated with the antibiotic penicillin until many resistant strains appeared. Gonorrhoea is spread by sexual contact. The spread can be controlled by treatment with antibiotics or the use of a barrier method of contraception such as a condom.
HIV initially causes a ‘flu like illness’. Unless successfully treated with antiretroviral drugs the virus attacks the body’s immune cells. Latestage HIV, or AIDS, occurs when the body’s immune system is no longer able to deal with other infections or cancers. HIV is spread by sexual contact or exchange of body fluids such as blood.

Scientific, Practical and Mathematical Skills

WS 1.4

Explain applications of science to prevent the spread of diseases.

Defences Against Pathogens

GCSE Science Subject Content

Describe the nonspecific defence systems of the human body against pathogens.

Details of the Science Content

The human body defends itself against the entry of pathogens in the following ways:

• the skin is a barrier and produces antimicrobial secretions

• the nose catches particles

• the trachea and bronchi secrete mucus that is moved by cilia

• the stomach produces acid, which kills the majority of pathogens that enter via the mouth.

The Human Immune System

GCSE Science Subject Content

Explain the role of the immune system of the human body in defence against disease.

Details of the Science Content

f a pathogen enters the body the immune system tries to destroy the pathogen. White blood cells are an important part of the immune system. They help to defend against pathogens through:

• phagocytosis

• producing antibodies

• producing antitoxins.

Vaccination

GCSE Science Subject Content

Explain the use of vaccines in the prevention and treatment of disease.

Details of the Science Content

Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies. If the same pathogen re-enters the body the white blood cells respond quickly to produce antibodies, preventing infection.
If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced. Students do not need to know details of vaccination schedules and side effects associated with specific vaccines.

Medicines

GCSE Science Subject Content

Explain the use of medicines in the prevention and treatment of disease.

Explain that many useful materials are formulations of mixtures.

Details of the Science Content

Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body. It is important that specific bacteria should be treated by specific antibiotics.
The use of antibiotics has greatly reduced deaths from infectious bacterial diseases. However, the emergence of strains of bacteria resistant to antibiotics is becoming a serious threat.
Antibiotics cannot kill viral pathogens. Painkillers and other medicines are used to treat the symptoms of disease. They do not kill pathogens.

Most medicines are mixtures. They are formulations made by mixing the ingredients in carefully measured quantities to ensure that the product has the required properties. One or more of the ingredients may be the drug, such as aspirin, but other ingredients make it easier or more pleasant for a patient to take the drug in solution or as a capsule or tablet.

Scientific, Practical and Mathematical Skills

This topic links with Variation and evolution (page 82).

Testing New Drugs

GCSE Science Subject Content

Describe the process of discovery and development of potential new medicines, including preclinical and clinical testing.

Details of the Science Content

When new medical drugs are devised, they have to be extensively tested and trialled before being used. Drugs are tested in a series of stages to find out if they are safe and effective.
New drugs are extensively tested for toxicity, efficacy and dose:

• in the laboratory, using cells, tissues and live animals

• then in clinical trials involving healthy volunteers and patients. Very low doses of the drug are given at the start of the clinical trial. If the drug is found to be safe, further clinical trials are carried out to find the optimum dose for the drug.

In double-blind trials, some patients are given a placebo. Patients are allocated randomly to groups so that neither the doctors nor the patients know who has received a placebo and who has received the drug until the trial is complete.

Scientific, Practical and Mathematical Skills

WS 1.6

Explain that the results of testing and trials, like the findings of all scientific research, are published only after evaluation by peer review.

Genetic Modification

GCSE Science Subject Content

Explain some of the possible benefits and risks, including practical and ethical considerations, of
using gene technology in modern medicine.

Details of the Science Content

New medical products have been produced by genetically modifying bacteria. Insulin for the treatment of Type 1 diabetes is produced by cultivating genetically modified bacteria.
Sheep and goats have been genetically modified to produce chemicals in their milk that can be used to treat disease. In one example the milk produced contains a protein needed to treat patients with cystic fibrosis.
Research is also exploring the possibility of providing tissues needed for transplants from animals that have been genetically modified so that the tissues are not rejected by the human immune system.

Scientific, Practical and Mathematical Skills

WS 1.3

Evaluate gene technologies, taking into account benefits, risks, and the ethical issues raised by the use of animals in medical research. This topic links with Variation and evolution (page 82).

Stem Cells

GCSE Science Subject Content

Discuss potential benefits and risks associated with the use of stem cells in medicine.

Details of the Science Content

One medical use of stem cells is well established: this is the use of stem cells from bone marrow in transplants to provide a supply of new blood cells for the person receiving the transplant. This is used to treat leukaemia. Stem cells for research may be based on:

• stem cells from embryos that are a few days old

• adult stem cells from selected parts of the body such as bone marrow

• fetal stem cells taken from blood in the umbilical cord.

Embryonic stem cells can develop into any of the many types of cells in the body. Adult stem cells can only give rise to the types of cells found in the tissues that the adult stem cells come from. Most medical uses of stem cells are still experimental. Treatments based on stem cells are being investigated for treating diseases such as:

• heart disease – using the patient’s own stem cells from bone marrow
• Type 1 diabetes – using embryo or fetal stem cells.

The properties of stem cells are not fully understood. Scientists do not yet know how their differentiation is controlled. This means that there is a fear that their ability to proliferate could lead to cancer when they are transplanted into a patient.

Scientific, Practical and Mathematical Skills

WS 1.3

Give a simple ethical argument about the rights and wrongs of the uses of stem cells. Evaluate possible uses of stem cells taking into account benefits, risks and the ethical issues raised by sources of the cells.

Interactions Between Different Types of Disease

GCSE Science Subject Content

Describe the interactions between different types of disease.

Details of the Science Content

Different types of disease may interact. Some examples include:
• defects in the immune system mean that an individual is more likely to suffer from infectious diseases
• viruses living in cells can be the trigger for cancers
• immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma
• severe physical ill health can lead to depression and other mental illness.

Development of the Earth’s Atmosphere

GCSE Science Subject Content

Describe how it is thought an oxygen-rich atmosphere developed over time.

Details of the Science Content

Evidence for the early atmosphere is limited because of the time scale of 4.6 billion years.
One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity, which released gases that formed the early atmosphere and water vapour that condensed to form the oceans. At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting mainly of carbon dioxide with little or no oxygen gas.
Volcanoes also produced nitrogen, which gradually built up in the atmosphere, and there may have been small proportions of methane and ammonia. When the oceans formed, carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the
amount of carbon dioxide in the atmosphere.
Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis. Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.
Photosynthesis by algae and plants also decreased the percentage of carbon dioxide in the atmosphere. Carbon dioxide was also used up in the formation of sedimentary rocks, such as limestone, and fossil fuels such as coal, natural gas and oil.

Scientific, Practical and Mathematical Skills

WS 1.1

Given appropriate information, interpret evidence and evaluate different theories about the Earth’s early atmosphere.

WS 1.3

Explain why evidence is uncertain or incomplete in a complex context.

MS 1c

Use ratios, fractions and percentages.

The Carbon Cycle

GCSE Science Subject Content

Recall that many different materials cycle through the abiotic and biotic components of an ecosystem.
Explain the importance of the carbon cycle to living organisms. Describe photosynthetic organisms as the main producers of food and therefore biomass for life on Earth.
Explain the role of microorganisms in the cycling of materials through an ecosystem.

Details of the Science Content

The element carbon is found as carbon dioxide in the atmosphere, dissolved in the water of the oceans, as calcium carbonate in sea shells, in fossil fuels and in limestone rocks, and as carbohydrates and other large molecules in all living organisms. Carbon cycles through the
environment by processes that include photosynthesis, respiration, combustion of fuels and the industrial uses of limestone.
Life depends on photosynthesis in producers such as green plants, which make carbohydrates from carbon dioxide in the air.
Animals feed on plants, passing the carbon compounds along food chains. Animals and plants respire and release carbon dioxide back into the air.
Decay of dead plants and animals by microorganisms returns carbon to the atmosphere as carbon dioxide and mineral ions to the soil.

Scientific, Practical and Mathematical Skills

WS 1.2

Draw and interpret diagrams to represent the main stores of carbon and the flows of carbon between them in the cycle. This topic links with Ecosystems and biodiversity (page 75).

The Greenhouse Effect

GCSE Science Subject Content

Describe the greenhouse effect in terms of the interaction of radiation with matter. (HT only) Recall that different substances may absorb, transmit or reflect these waves in ways that vary with wavelength.

Details of the Science Content

Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life. They allow short-wavelength radiation from the Sun to pass through the atmosphere to the Earth’s surface but absorb the outgoing longwavelength radiation from the Earth’s surface, causing an increase in temperature. Water vapour, carbon dioxide and methane are greenhouse gases that increase the absorption of outgoing, long-wavelength radiation.

Scientific, Practical and Mathematical Skills

WS 1.2

Interpret and draw diagrams to describe the greenhouse effect.

Human Impacts on the Climate

GCSE Science Subject Content

Evaluate the evidence for additional anthropogenic causes of climate change, including the correlation between change in atmospheric carbon dioxide concentration and the consumption of fossil fuels, and describe the uncertainties in the evidence base.

Details of the Science Content

Human activities that involve burning fossil fuels (coal, oil and gas) for generating electricity, transport and industry all add carbon dioxide to the atmosphere. These activities have led to a large rise in the
concentration of carbon dioxide in the air over the last 150 years. Over the same time the average temperature of the surface of the Earth has risen. The scientific consensus is that this is more than correlation and that the rise in greenhouse gas concentrations has caused the rise in temperature.
Climate describes the long-term patterns of weather in different parts of the world. Climate change is shown by changes to patterns in measures of such things as air temperature, rainfall, sunshine and wind speed.
Scientists analyse data on climate change using computer models based on the physics that describes the movements of mass and energy in the climate system. Many complex changes on Earth affect the climate, and detailed data about the scale of the changes is not available from all over the world. Also, when predicting climate change, scientists have to make assumptions about future
greenhouse gas emissions. This means that there are uncertainties in the predictions.

Scientific, Practical and Mathematical Skills

WS 1.6

Explain the importance of scientists publishing their findings and theories so that they can be evaluated critically by other scientists. Understand that the scientific consensus about global warming and climate change is based on systematic reviews of thousands of peer reviewed publications.

WS 1.3

Explain why evidence is uncertain or incomplete in a complex context.

MS 2c, 4a

Extract and interpret information from charts, graphs and tables.

MS 2h
Use orders of magnitude to evaluate the significance of data.

Climate Change: Impacts and Mitigation

GCSE Science Subject Content

Describe the potential effects of increased levels of carbon dioxide and methane on the Earth’s climate and how these effects may be mitigated, including consideration of scale, risk and environmental implications.

Details of the Science Content

Consequences of global warming and climate change include:

• sea-level rise

• loss of habitats

• changes to weather extremes

• changes in the amount, timing and distribution of rainfall

• temperature and water stress for humans and wildlife

• changes in the distribution of species

• changes in the food-producing capacity of some regions.
Steps can be taken to mitigate the effects of climate change by reducing the overall rate at which greenhouse gases are added to the atmosphere. Examples of mitigation include:

• using energy resources more efficiently
• using renewable sources of energy in place of fossil fuels

(see Resources of materials and energy (page 141))

• reducing waste by recycling
• stopping the destruction of forests
• regenerating forests
• developing techniques to capture and store carbon dioxide from power stations

Scientific, Practical and Mathematical Skills

WS 1.4

In the context of climate change, evaluate associated economic and environmental implications; and make decisions based on the evaluation of evidence and arguments.

Pollutants that affect air quality

GCSE Science Subject Content

Describe the major sources of carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates in the atmosphere and explain the problems caused by increased amounts of these substances.

Details of the Science Content

The combustion of fuels is a major source of atmospheric pollutants that can be harmful to health and the environment.
Carbon monoxide is formed by the incomplete combustion of hydrocarbon fuels when there is not enough air. Carbon monoxide is a toxic gas that combines very strongly with haemoglobin in the blood. At low doses it puts a strain on the heart by reducing the capacity of the blood to carry oxygen. At high doses it kills.
Sulfur dioxide is produced by burning fuels that contain some sulfur. These include coal in power stations and some diesel fuel burnt in ships and heavy vehicles. Sulfur dioxide turns to sulfuric acid in moist air.
Oxides of nitrogen are produced by the reaction of nitrogen and oxygen from the air at the high temperatures involved when fuels are burned.
Sulfur dioxide and oxides of nitrogen cause respiratory problems in humans and cause acid rain. Acid rain damages plants and buildings. It also harms living organisms in ponds, rivers and lakes.
Particulates in the air include soot (carbon) from diesel engines and dust from roads and industry. The smaller particulates can go deep into people’s lungs and cause damage that can lead to heart disease and lung cancer.

Scientific, Practical and Mathematical Skills

WS 1.4

Describe, explain or evaluate ways in which human activities affect the environment.

The Water Cycle

GCSE Science Subject Content

Explain the importance of the water cycle to living organisms.

Details of the Science Content

Scientific, Practical and Mathematical Skills

WS 1.2

Draw and interpret diagrams to represent the main stores of water and the flows of water between them in the cycle.

Sources of Potable Water

GCSE Science Subject Content

Describe the principal methods for increasing the availability of potable water in terms of the separation techniques used, including ease of treatment of waste, ground and salt water.
Describe, explain and exemplify the processes of simple distillation.

Details of the Science Content

Water that is safe to drink is called potable water. Potable water is not pure water in the chemical sense because it contains dissolved substances.
The methods used to produce potable water depend on available supplies of water and local conditions. In the UK, rain provides water with low levels of dissolved substances (fresh water)
that collects in the ground and in lakes and rivers and most potable water is produced by:

• choosing an appropriate source of fresh water

• passing the water through filters

• sterilising.

Sterilising agents used for potable water include chlorine, ozone or ultraviolet light. If supplies of fresh water are limited, desalination of salty water or sea water may be required. Desalination can be done by distillation or by processes that use membranes such as reverse osmosis. Energy resources have to be used to run these processes. Urban lifestyles and industrial processes produce large amounts of waste water that require treatment before being released into the environment. Sewage and agricultural waste water require removal of organic matter and harmful microbes. Industrial waste water may require removal of organic matter and harmful chemicals.
Sewage treatment includes:
• screening and grit removal
• sedimentation to produce sewage sludge and effluent
• anaerobic digestion of sewage sludge
• aerobic biological treatment of effluent.

Scientific, Practical and Mathematical Skills

WS 1.4

Explain everyday and technological applications of science; evaluate associated personal, social, economic and environmental implications with reference to the sources of potable water and treatment of waste water

Ecosystems and Biodiversity

GCSE Science Subject Content

Describe different levels of organisation in an ecosystem from individual organisms to the whole ecosystem.

Details of the Science Content

An ecosystem is made up of all the living organisms in a particular environment together with the non-living components such as soil, air and water. A habitat is where a particular organism lives in an ecosystem. A population is made up of all the individuals of the same species in a habitat. A community is made up of all the populations of different organisms that live in the same habitat. Feeding relationships within a community can be represented by food chains. All food chains
begin with a producer that synthesises molecules. This is usually a green plant, which absorbs light to make glucose.
A food web can be used to understand the interdependence of species within an ecosystem in terms of food sources. Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers and then tertiary consumers. Consumers that kill and eat other animals are
predators, and those eaten are prey. In a community the numbers of predators and prey rise and fall in cycles.

Scientific, Practical and Mathematical Skills

WS 1.2

Interpret graphs used to model predator–prey cycles.

Interdependence and Competition

GCSE Science Subject Content

Describe the importance of interdependence and competition in a community.

Details of the Science Content

To survive and reproduce, organisms require a supply of materials from their surroundings and from the other living organisms in an ecosystem. Plants often compete with each other for light and space, and for water and nutrients from the soil. Animals often compete with each other for food, mates and territory. Within a community each species depends on other species for food, shelter, pollination, seed dispersal etc. If one species is removed it affects the whole community. A stable community is one where all the species and environmental factors are in balance so that population sizes remain fairly constant.

Factors that Affect Communities

GCSE Science Subject Content

Explain how some abiotic and biotic factors affect communities.

Details of the Science Content

Abiotic factors that can affect a community are:

• light intensity

• temperature

• moisture levels

• soil pH and mineral content

• wind intensity and direction

• carbon dioxide levels for plants

• oxygen levels for aquatic animals.

Biotic factors that can affect a community are:

• availability of food
• new predators arriving
• new diseases
• one species outcompeting another.

Scientific, Practical and Mathematical Skills

WS 1.2

Predict how a change in an abiotic, or biotic, factor would affect a given community given appropriate data or context.

MS 1c

Calculate the percentage of mass.

MS 2c, 4a

Extract and interpret information from charts, graphs and tables.

Field Investigations

GCSE Science Subject Content

Describe how to carry out a field investigation into the distribution and abundance of organisms in an
ecosystem and explain how to determine their numbers in a given area.

Details of the Science Content

Ecologists use a range of investigation methods using transects and quadrats to determine the distribution and abundance of species in an ecosystem.

Scientific, Practical and Mathematical Skills

MS 2b

Calculate arithmetic means.

WS 3.3

Carry out and represent mathematical and statistical analysis.

MS 4a, 4c

Plot and draw appropriate graphs, selecting appropriate scales for the axes.

MS 2d
Understand the principles of sampling as applied to scientific data.

Biodiversity

GCSE Science Subject Content

Explain some of the benefits and challenges of maintaining local and global biodiversity.

Details of the Science Content

Biodiversity is greater in ecosystems that provide a bigger range of different habitats, which are home to larger populations of a variety of organisms. Small populations are in greater danger of dying out if an ecosystem is disrupted in some way. Ecosystems with high levels of biodiversity help to provide the resources needed to sustain life, including human life. Ecosystems with higher biodiversity offer economic benefits by sustaining the resources needed for agriculture, fishing and forestry.

Negative Human Impacts on Ecosystems

GCSE Science Subject Content

Describe negative human interactions within ecosystems and explain their impact on biodiversity.

Details of the Science Content

Examples of human interactions with local ecosystems that can diminish or destroy biodiversity include:

• building, quarrying, farming, clearing woods and other activities that destroy habitats

• the destruction of peat bogs, and other areas of peat, to produce garden compost

• pollution of streams, rivers and lakes by sewage, toxic wastes and fertilisers.

An example of a global impact of human activities is global warming leading to climate
change (The Earth’s atmosphere (page 67)).

Scientific, Practical and Mathematical Skills

WS 1.4
Evaluate given information about ways in which human activities affect the environment.

Positive Human Impacts on Ecosystems

GCSE Science Subject Content

Describe positive human interactions within ecosystems and explain their impact on biodiversity.

Details of the Science Content

There are programmes to reduce these negative effects on ecosystems and biodiversity. These include:

• breeding programmes for endangered species
• protecting and regenerating habitats
• reintroducing wider field margins and hedgerows in areas of monoculture
• recycling resources rather than dumping waste in landfill
• production of peat-free composts
• reducing deforestation and carbon dioxide emissions.

Scientific, Practical and Mathematical Skills

WS 1.4

Evaluate given information about methods that can be used to tackle problems caused by human impacts on the environment.

Inheritance

Chromosomes and Genes

GCSE Science Subject Content

Explain the following terms: gamete, chromosome and gene. Describe DNA as a polymer made up of
two strands forming a double helix.
Describe the genome as the entire genetic material of an organism.

Details of the Science Content

Sexual reproduction involves the joining (fusion) of male and female gametes (sperm and egg cells in animals). In sexual reproduction there is mixing of genetic information, which leads to variety in the
offspring. The formation of gametes involves meiosis.
The genetic material in the nucleus of a cell is composed of a chemical called DNA contained in the chromosomes. Human body cells contain 23 pairs of chromosomes. DNA is made of very large molecules in long strands, twisted to form a double helix.
A gene is a small section of DNA on a chromosome. Each gene contains the code for a particular combination of amino acids to make a specific protein. The genome of an organism is made up of all the genes in the DNA of its body cells.

Scientific, Practical and Mathematical Skills

This topic has links with Cells in animals and plants (page 27).

Sex Determination in Humans

GCSE Science Subject Content

Describe sex determination in humans.

Details of the Science Content

In human cells, one of the 23 pairs of chromosomes carries the genes that determine sex. In females the sex chromosomes are the same (XX); in males the chromosomes are different (XY). All eggs contain an X chromosome. Sperm cells contain either an X or a Y chromosome.

Single Gene Inheritance

GCSE Science Subject Content

Explain single gene inheritance. Predict the results of single gene crosses. Explain the terms allele/variant, dominant, recessive, homozygous, heterozygous.

Details of the Science Content

Some characteristics are controlled by a single gene. Examples are fur colour in mice and red–green colour blindness in humans. Each gene may have different forms called alleles. A dominant allele is always expressed, even if only one copy is present. A recessive allele is only expressed if two copies are present (therefore no dominant allele present). If the two alleles present are the same the organism is homozygous for that trait, but if the alleles are different they are heterozygous.

Scientific, Practical and Mathematical Skills

WS 1.2

Complete a Punnett square diagram or interpret the results of a genetic cross diagram for a single gene, and understand family trees.

MS 2e (HT only)

Construct a Punnett square diagram to make predictions based on simple probability.

MS 1c

Use direct proportion and simple ratios in genetic crosses.

Genotype and Phenotype

GCSE Science Subject Content

Describe simply how the genome, and its interaction with the environment, influences the development of the phenotype of an organism. Explain the terms genotype and phenotype.
Recall that most phenotypic features are the result of multiple genes rather than single gene inheritance.

Details of the Science Content

All the genes present in an individual organism interact with the environment in which the organism grows and develops its observable appearance and character. These
characteristics are its phenotype.
The variation in the characteristics of individuals of the same kind may be due to
differences in:

• the genes they have inherited (genetic causes)

• the conditions in which they have developed (environmental causes)

• a combination of genes and the environment.

Human height is an example of a characteristic determined by many genes, each with different alleles. The set of alleles that determine the height of a person is the genotype for that characteristic. Height is also affected by diet and exercise which are part of the environment in which an individual grows up.

Scientific, Practical and Mathematical Skills

.WS 1.2

Explain why studies involving identical twins help to separate the contribution of genes and the environment to the development of their phenotypes.

WS 1.1

Given a context and related information, discuss the potential importance for medicine of our increasing understanding of the human genome.

Variation and Evolution

Mutations

GCSE Science Subject Content

State that there is usually extensive genetic variation within a population of a species. Recall that all variants arise from mutations, and that most have no effect on the phenotype, some influence the
phenotype and a very few determine the phenotype.

Details of the Science Content

Mutations are changes in DNA molecules that may affect genes. Mutation of a gene can alter the proteins that it contains the code for, or even prevent the protein being produced in cells.
Mutations can happen when DNA is copied during cell division or when cells are affected by environmental factors such as ionising radiation.

Evolution through Natural Selection

GCSE Science Subject Content

Describe evolution as a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of new species.
Explain how evolution occurs through natural selection of variants that give rise to phenotypes best suited to their environment.

Details of the Science Content

The theory of evolution by natural selection explains the evolution of all species of living things from simple life forms that first developed more than three billion years ago. If two populations of one species become isolated geographically or environmentally they may evolve in different ways to suit different conditions. If they become so different that they can no longer interbreed to produce fertile
offspring they have formed two new species.

Scientific, Practical and Mathematical Skills

WS 1.2

Use the theory of evolution by natural selection in an explanation.

Evidence for Evolution

GCSE Science Subject Content

Describe the evidence for evolution, including fossils and antibiotic resistance in bacteria.

Details of the Science Content

Evidence for evolution comes from the study of fossils that show how much or how little different organisms have changed as life developed on Earth. Evolution of bacteria can be observed happening in a much shorter time because they reproduce so fast. Bacteria that cause disease evolve by natural selection when exposed to antibiotics; this gives rise to a resistant strain

Scientific, Practical and Mathematical Skills

MS 2c, 4a

Extract and interpret information from charts, graphs and tables.

Identification and Classification of Living things

GCSE Science Subject Content

Describe the impact of developments in biology on classification systems.

Details of the Science Content

In studies of evolution it is essential to be able to identify and classify living things. Traditionally living things have been classified into groups depending on their structure and characteristics.
Organisms are named by the binomial system of genus and species. As evidence of internal structures became more developed due to improvements in microscopes and progress with the
understanding of biochemical processes, new models of classification have been proposed.
Modern classifications systems are based on theories about evolution developed from analysis of differences in DNA molecules.

Scientific, Practical and Mathematical Skills

WS 1.1

Show how new methods of investigation and new discoveries led to new scientific ideas.

Selective Breeding

GCSE Science Subject Content

Explain the impact of the selective breeding of food plants and domesticated animals.

Details of the Science Content

Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic traits.
Selective breeding involves choosing parents from a mixed population with the desired characteristic. They are bred together. From the offspring those with the desired characteristic are bred together. This continues over many generations until all the offspring
show the desired characteristic.
The trait can be chosen for usefulness or appearance. Selective breeding can lead to ‘inbreeding’
where some breeds are particularly prone to disease or inherited defects.

Scientific, Practical and Mathematical Skills

WS 1.3, 1.4

Evaluate the benefits and risks of selective breeding given appropriate information and consider related ethical issues.

Genetic Engineering

GCSE Science Subject Content

Describe genetic engineering as a process which involves modifying the genome of an organism to introduce desirable characteristics.
(HT only) Describe the main steps in the process of genetic engineering.
Explain some of the possible benefits and risks, including practical and ethical considerations, of
using gene technology in modern agriculture.

Details of the Science Content

In genetic engineering, selected genes from one organism are transferred to another organism which may, or may not, belong to the same species. This process for genetic modification uses enzymes and vectors (such as bacterial plasmids or viruses) to transfer genes. It is much faster than selective breeding.
Genes can be transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with the desired characteristics.
Crops that have had their genes modified in this way are called genetically modified crops (GM crops). Crops can be genetically modified to give increased yields or to increase the amount of a vitamin in the food from the crop.
Genetically modified crops also include ones that are resistant to insect attack or to herbicides. This means that farmers can cut down on the use of pesticides. They can also spray to kill weeds while leaving the crop plant unaffected.
Concerns about GM crops include the effect on populations of wild flowers and insects as a result of cross-pollination. Insects may evolve to become resistant so that the GM crops are no longer protected.

Scientific, Practical and Mathematical Skills

WS 1.4

Evaluate the advantages and disadvantages of GM technologies based on data or other information.

WS 1.3

Give a simple ethical argument about the rights and wrongs of a GM technology. Recognise, in given information, the difference between a practical and an ethical argument.

The Periodic Table

Atomic Number and the Periodic Table

GCSE Science Subject Content

Explain how the position of an element in the periodic table is related to the arrangement of electrons in its atoms and hence to its atomic number.

Explain in terms of isotopes how this changes the arrangement proposed by Mendeleev.

Details of the Science Content

The elements in the periodic table are arranged in order of atomic (proton) number, so that elements with similar properties are in columns known as groups. The table is called a periodic table because similar properties occur at regular intervals.
Electrons occupy particular energy levels. Each electron in an atom is at a particular energy level (in a particular shell). The electrons in an atom occupy the lowest available energy levels (innermost available shells). Elements in the same group in the periodic table have the same number of electrons in their outer shell (outer electrons) and this gives them similar chemical properties.

Following Mendeleev, the elements in the periodic table were arranged in order of relative atomic mass. In this order some elements appeared to be in the wrong group. These problems were solved once it was realised that most elements occur as mixtures of isotopes and that elements should be
arranged in the table in order of atomic number.

Scientific, Practical and Mathematical Skills

WS 1.2

Represent the electronic structure of the first 20 elements of the periodic table in the following forms:
sodium
2,8,1
Predict possible reactions and probable reactivity of elements from their positions in the periodic table.
This topic links with Atomic structure (page 24).

WS 1.1

Show how scientific methods and theories have changed over time. This topic links with Atomic structure (page 24).

Metals and Non-metals

GCSE Science Subject Content

Explain how the atomic structure of metals and non-metals relates to their position in the periodic table. Explain how the reactions of elements are related to the arrangement of electrons in their atoms and hence to their atomic number.

Details of the Science Content

The majority of elements are metals. Metals are found to the left and towards the bottom of the periodic table. Non-metals are found towards the right and top of the periodic table.
Elements that react by losing their outer electrons to form positive ions are metals.
Elements that do not form positive ions are non-metals. The more reactive non-metals, such as the halogens, react with metals by gaining electrons to form negative ions.

Scientific, Practical and Mathematical Skills

WS 1.2
Describe metals and non-metals and explain the differences between them in terms of their characteristic physical and chemical properties (see Structure and bonding (page 98) and the sections about groups 1, 7 and 0 in this topic).

Group 0

GCSE Science Subject Content

Recall the simple
properties of Group 0.
Explain how the observed simple properties of Group 0 depend on the outer shell of electrons of the atoms and predict properties from given trends down the group.

Details of the Science Content

The elements in Group 0 of the periodic table are called the noble gases. They are unreactive
and do not easily form molecules because their atoms have stable arrangements of electrons.
The noble gases have eight electrons in their highest energy level (outer shell), except for
helium, which has only two electrons.
The boiling points of the noble gases increase with increasing relative atomic mass (going
down the group).

Scientific, Practical and Mathematical Skills

WS 1.2

Predict properties from given trends down Group 0.

Group 1

GCSE Science Subject Content

Recall the simple properties of Group 1.
Explain how the observed simple properties of Group 1 depend on the outer shell of electrons of the atoms and predict properties from given trends down the group.

Details of the Science Content

The elements in Group 1 of the periodic table are known as the alkali metals. They:

• are soft metals with low density

• react with non-metals, including chlorine and oxygen, to form colourless ionic compounds

• react with water

• form hydroxides that give alkaline solutions in water.

In Group 1, the further down the group an element is, the more reactive the element.

Scientific, Practical and Mathematical Skills

WS 1.2
Predict properties from given trends down Group 1.

Group 7

GCSE Science Subject Content

Recall the simple properties of Group 7.
Explain how the observed simple properties of Group 7 depend on the outer shell of electrons of the atoms and predict properties from given trends down the group.

Details of the Science Content

The elements in Group 7 of the periodic table are known as the halogens. They:

• are non-metals

• consist of molecules

• react with metals to form ionic compounds

• form molecular compounds with other non-metallic elements.

In Group 7, the further down the group an element is the higher its relative molecular mass, melting point and boiling point.
In Group 7, reactivity of the elements decreases going down the group. A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.

Scientific, Practical and Mathematical Skills

WS 1.2

Predict properties from given trends down Group 7.

Chemical Quantities

Chemical Equations

GCSE Science Subject Content

Use the names and symbols of common elements and
compounds and the principle of conservation of mass to write formulae and
balanced chemical equations. (HT only) and half equations.
Use chemical symbols to write the formulae of elements and simple covalent and ionic compounds.
Describe the physical states of products and reactants using state symbols (s, l, g and aq).

Details of the Science Content

Atoms of each element are represented by a chemical symbol, eg O represents an atom of oxygen, Na represents an atom of sodium.
There are about 100 different elements.
Elements are shown in the periodic table.
Compounds are formed from elements by chemical reactions.
Compounds contain two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were
formed. Compounds can only be separated into elements by chemical reactions.
Chemical reactions always involve the formation of one or more new substances, and often involve a detectable energy change. Chemical reactions can be represented by word equations or equations using symbols and formulae.
In chemical equations, the three states of matter are shown as (s), (l) and (g), with (aq) for aqueous solutions.

Scientific, Practical and Mathematical Skills

WS 4.1
Use the names and symbols of the first 20 elements, groups 1, 7 and 0 and other common elements from a supplied periodic table to write formulae and balanced chemical equations where appropriate.
Name compounds of these elements from given formulae or symbol equations.
Write word equations for the reactions in this specification.
Write formulae and balanced chemical equations for the reactions in this specification.

Conservation of Mass

GCSE Science Subject Content

Recall and use the law of conservation of mass.

Explain any observed changes in mass in non-enclosed systems during a chemical reaction and explain them using the particle model.

Details of the Science Content

The law of conservation of mass states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants. This means that chemical reactions can be represented by symbol equations that are balanced in terms of the numbers of atoms of each element involved on both sides of the equation.

Some reactions may appear to involve a change in mass but this can usually be explained because a reactant or product is a gas and its mass has not been taken into account.

Scientific, Practical and Mathematical Skills

MS 1a
Use arithmetic computation and ratio when writing and
balancing equations.

WS 1.2
Explain any observed changes in mass in nonenclosed systems during a chemical reaction given the balanced symbol
equation for the reaction.

Relative Formula Masses

GCSE Science Subject Content

Calculate relative formula masses of species separately and in a balanced chemical equation.
Students should be able to calculate the percentage by mass in a compound given the relative formula mass and the relative atomic masses.

Details of the Science Content

The relative atomic mass of an element compares the mass of atoms of the element with the 12C isotope. It is an average value for the isotopes of the element.
The relative formula mass (Mr) of a compound is the sum of the relative atomic masses of the atoms in the numbers shown in the formula.
In a balanced chemical equation, the sum of the relative formula masses of the reactants in the quantities shown equals the sum of the relative formula masses of the products in the quantities shown.
Students will not be expected to calculate relative atomic masses from isotopic abundances

Scientific, Practical and Mathematical Skills

MS 1a, 3a

Calculate the relative formula mass (Mr ) of a compound from its formula, given the relative atomic masses.

WS 3.3

Carry out and represent mathematical and statistical analysis.

Amounts in Moles (HT only)

GCSE Science Subject Content

Explain how the mass of a given substance is related to the amount of that substance in moles and vice versa.
Recall and use the definitions of the Avogadro constant (in standard form) and of the mole.

Details of the Science Content

Chemical amounts are measured in moles. The symbol for the unit mole is mol. The mass of one mole of a substance in grams is numerically equal to its relative formula mass.
One mole of a substance contains the same number of the stated particles, atoms, molecules or ions as one mole of any other substance.
The number of atoms, molecules or ions in a mole of a given substance is the Avogadro constant. The value of the Avogadro constant is 6.02 × 1023 per mole.

Scientific, Practical and Mathematical Skills

MS 1a, 1b, 1c, 2a

Recognise and use expressions in decimal form when using the relative formula mass of a substance to calculate the amount in moles in a given mass of that substance and vice versa, giving the answer in the appropriate units.

MS 3b, 3c

Change the subject of a mathematical equation.

WS 4.6, MS 2a

Provide answers to an appropriate number of significant figures.

MS 1b

Calculate with numbers written in standard form when using the Avogadro constant.

MS 3a

Understand and use the symbols: =, <, <<, >>, >, ∝ , ~

Calculations Based on Equations (HT only)

GCSE Science Subject Content

Deduce the stoichiometry of an equation from the masses of reactants and products and explain the effect of a limiting quantity of a reactant.

Use a balanced equation to calculate masses of reactants or products.

Details of the Science Content

The balancing numbers in a symbol equation can be calculated from the masses of reactants and products by converting the masses in grams to amounts in moles and converting the numbers of moles to simple whole number ratios.
In a chemical reaction involving two reactants, it is common to use an excess of one of the reactants to ensure that all of the other reactant is used. The reactant that is completely used up is called the limiting reactant.

The masses of reactants and products can be calculated from balanced symbol equations.
Chemical equations can be interpreted in terms of moles. For example:

Mg + 2HCl → MgCl2 + H2

shows that one mole of magnesium reacts with two moles of hydrochloric acid to produce one mole of magnesium chloride and one mole of hydrogen gas.

Scientific, Practical and Mathematical Skills

MS 3c, 3d
Balance an equation given the masses of reactants and products.
Explain the effect of a limiting quantity of a reactant on the amount of products it is possible to obtain in terms of amounts in moles or masses in grams.

MS 1a, 1c, 3c, 3d

Calculate the masses of reactants and products from the balanced symbol equation and the mass of a given reactant or product.

WS 4.6, MS 2a

Provide answers to an appropriate number of significant figures.

Concentrations of Solutions

GCSE Science Subject Content

(HT only) Explain how the mass of a solute and the volume of the solution is related to the concentration of the solution.

Details of the Science Content

Many chemical reactions take place in solutions. The concentration of a solution can be measured in mass per given volume of solution, eg grams per dm³ (g/dm³ ).

Scientific, Practical and Mathematical Skills

MS 1c, 3c

Calculate the mass of solute in a given volume of solution of known concentration in terms of mass per given volume of solution.

Forces and Energy Changes

Forces as Vectors

GCSE Science Subject Content

Recall examples of ways in which objects interact: by gravity, electrostatics, magnetism and by contact (including normal contact force and friction), and describe how such examples involve interactions between pairs of objects which produce a force on each object, representing such forces as vectors.

Details of the Science Content

Scalar quantities have magnitude only. Vector quantities have magnitude and an associated direction.
Force is a vector quantity. A vector quantity may be represented by an arrow. The length of the arrow represents the magnitude, and the direction of the arrow the direction of the vector quantity.
A force is a push or pull that acts on an object due to the interaction with another object. All forces between objects are either:

• contact forces – the objects are physically touching
or

• non-contact forces – the objects are physically separated.

Resolving forces (HT only)

GCSE Science Subject Content

Describe examples of the forces acting on an isolated solid object or system; describe, using free body diagrams, examples where several forces lead to a resultant force on an object and the special case of balanced forces when the resultant force is zero (qualitative only).

Details of the Science Content

A number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together. This single force is called the resultant force. A free body diagram shows the magnitude and direction of the forces acting on an object. A single force can be resolved into two components acting at right angles to each other. The two component forces together have the same effect as the single force.

Scientific, Practical and Mathematical Skills

WS 1.2, MS 4a, 5a, 5b

Use vector diagrams to illustrate resolution of forces and equilibrium situations and determine the resultant of two forces, to include both magnitude and direction (scale drawings only).

Work

GCSE Science Subject Content

Describe and calculate the changes in energy involved when a system is changed by the work done by forces acting upon it.
Use the relationship between work done, force and distance moved along the line of action of the force, describing the energy transfer involved.

Details of the Science Content

A force does work on an object when the force causes a displacement of the object. work done = force × distance moved along the line of action of the force W = F s work done, W, in joules, J force, F, in newtons, N distance, s, in metres One joule of work is done when a force of one newton causes a displacement of one metre. 1 joule = 1 newton-metre

Scientific, Practical and Mathematical Skills

WS 1.2, MS 3b, 3c

Recall and apply this equation to calculate energy transfers.

WS 4.5, MS 1c, 3c

Convert between newton-metres and joules.

Mass and Weight

GCSE Science Subject Content

Define weight, describe how it is measured and describe the relationship between the weight of that body and the gravitational field strength.

Details of the Science Content

Weight is the force acting on an object due to gravity. The force of gravity close to the Earth is due to the gravitational field around the Earth.
The weight of an object depends on the gravitational field strength at the point where the object is:

weight = mass × gravitational field strength

W = m g
weight, W, in newtons , N
mass, m, in kilograms, kg
gravitational field strength, g, in newtons per
kilogram, N/kg

The weight of an object and the mass of an object are directly proportional. Weight is measured using a calibrated spring balance (a newtonmeter).

Scientific, Practical and Mathematical Skills

WS 1.2, MS 3b, 3c

Recall and apply this equation. In any calculation the value of the gravitational field strength (g) will be
given.

MS 3a
Understand and use the symbol for proportionality, ∝

Gravitational Potential Energy

GCSE Science Subject Content

Calculate the amounts of energy associated with an object raised above ground level.

Details of the Science Content

An object raised above ground level gains gravitational potential energy

g . p . e . = mass × gravitational f ield strength
× height

Ep = m g h

gravitational potential energy, Ep, in joules, J mass, m, in kilograms, kg
gravitational field strength, g, in newtons per kilogram, N/kg height, h, in metres, m

Scientific, Practical and Mathematical Skills

WS 1.2, MS 3c
Recall and apply this equation to calculate changes in stored energy.
In any calculation the value of the gravitational field
strength (g) will be given.

W
ethical issues.

Elastic Deformation

GCSE Science Subject Content

Explain, with examples, that to stretch, bend or compress an object, more than one force has to be applied. Describe the difference between elastic and inelastic distortions caused by stretching forces; describe the relationship between force and extension for a spring and other simple systems;
describe the difference between linear and non-linear relationships between force and extension, and calculate a spring constant in linear cases.

Details of the Science Content

An object that has been stretched has been elastically deformed if the object returns to its original length after the forces are removed. An object that does not return to its original length after the forces have been removed has been inelastically deformed.
The extension of an elastic object, such as a spring, is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.
force = spring constant x extension
[F = k e]
force, F, in newtons, N
spring constant, k, in newtons per metre, N/m
extension, e, in metres, m
A force that stretches (or compresses) a spring does work, and elastic potential energy is stored
in the spring. Provided the spring does not go past the limit of proportionality the work done on the spring and the elastic potential energy stored are equal.

Scientific, Practical and Mathematical Skills

WS 1.2, MS 3c, 4a, 4b, 4c

Recall and apply this equation

Energy Stored in a Stretched Spring

GCSE Science Subject Content

Calculate the amounts of energy associated with a stretched spring.

Details of the Science Content

Elastic potential energy is stored in a stretched
spring.
elastic potential energy = 0.5 × spring constant ×(extension)²
Ee = 1/2 k e²
(assuming the limit of proportionality has not been exceeded)
elastic potential energy, Ee, in joules, J spring constant, k, in ewtons per metre, N/m extension, e, in metres, m

Scientific, Practical and Mathematical Skills

WS 1.2, MS 1c, 3c
Calculate the work done in stretching.
MS 3b, 3c
Apply this equation, which is given on the Physics equations sheet.

Structure and Bonding

Types of Chemical Bonding

GCSE Science Subject Content

Describe and compare the nature and arrangement of chemical bonds in ionic compounds, simple
molecules, giant covalent structures, and polymers and metals.

Details of the Science Content

There are three types of strong chemical bonds: ionic, covalent and metallic.
For ionic bonding the particles are oppositely charged ions.
For covalent bonding the particles are atoms that share pairs of electrons.
For metallic bonding the particles are atoms that share delocalised electrons.
Ionic bonding occurs in compounds formed from metals combined with non-metals. Covalent bonding occurs in non-metallic elements and in compounds of non-metals. Metallic bonding occurs in metallic elements and alloys.

Ionic Bonding

GCSE Science Subject Content

Explain chemical bonding in terms of electrostatic forces and the transfer of electrons.
Construct dot and cross diagrams for simple ionic substances.
Deduce the empirical formula of a compound from the relative numbers of atoms present or from a
model or diagram and vice versa.
Use the formulae of common ions to deduce the formula of a compound.

Details of the Science Content

When a metal atom reacts with a non-metal atom electrons in the outer shell of the metal atom are transferred. Metal atoms lose electrons to become positively charged ions.
Non-metal atoms gain electrons to become negatively charged ions. The ions produced by metals in groups 1 and 2 and by non-metals in groups 6 and 7 have the electronic structure of a noble gas (Group 0).
The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram, eg for sodium chloride:

The charge on the ions produced by metals in groups 1 and 2 and by non-metals in groups 6 and 7 relates to the group number of the element in the periodic table.
An ionic compound is a giant structure of ions. Ionic compounds are held together by strong
electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called ionic bonding.
The structure of sodium chloride can be represented in the following forms:

Knowledge of the structures of specific ionic compounds other than sodium chloride is not required.

Scientific, Practical and Mathematical Skills

WS 1.2

Draw dot and cross diagrams for ionic compounds formed by metals in groups 1 and 2 with non-metals in groups 6 and 7. Work out the charge on the ions of metals and non-metals from the group number of the element, limited to the metals in groups 1 and 2, and non-metals in groups 6 and 7. Describe the limitations of particular representations and models to include dot and cross diagrams, ball and stick models and two- and three dimensional representations.

MS 4a

Translate data between diagrammatic and numeric forms.

MS 5b

Draw or complete diagrams to represent 2D and 3D forms including twodimensional representations of 3D structures.

MS 1a

Use arithmetic computation and ratio when determining empirical formulae.

Properties of Ionic Compounds

GCSE Science Subject Content

Explain how the bulk properties of materials are related to the different types of bonds they contain, their bond strengths and the ways in which their bonds are arranged, recognising that the atoms themselves do not have these properties.

Details of the Science Content

Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions.
These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds.
When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.

Scientific, Practical and Mathematical Skills

WS 1.2

Use ideas about energy transfers and the relative strength of chemical bonds and intermolecular forces to explain the different temperatures at which changes of state occur. Use data to predict states of substances under given conditions.

Covalent Bonding

GCSE Science Subject Content

Explain chemical bonding in terms of electrostatic forces and the sharing of electrons.
Construct dot and cross diagrams for simple covalent substances.
Deduce the empirical formula of a compound from the relative numbers of atoms present or from a
model or diagram and vice versa..

Details of the Science Content

When atoms share pairs of electrons they form covalent bonds. These bonds between atoms are strong. Covalently bonded substances may consist of small molecules. Some covalently bonded substances have very large molecules, such as polymers. Some covalently bonded substances have giant covalent structures, such as diamond and silicon dioxide.
The covalent bonds in molecules and giant structures can be represented in the following forms:

Scientific, Practical and Mathematical Skills

WS 1.2

Recognise substances as small molecules, polymers or giant structures from diagrams showing their bonding. Draw dot and cross diagrams for the molecules of hydrogen, chlorine, oxygen, nitrogen, hydrogen chloride, water, ammonia and methane. Represent the covalent bonds in small molecules, in the repeating units of polymers and in part of giant covalent structures, using a line to represent a single bond.

Describe the limitations of particular representations and models to include dot and cross diagrams, ball and stick models and two- and three dimensional representations.

MS 5b

Draw or complete diagrams to represent 2D and 3D forms including two dimensional representations of 3D molecules.

MS 1a

Use arithmetic computation and ratio when determining empirical formulae.

Properties of Substances with Covalent Bonding

GCSE Science Subject Content

Explain how the bulk properties of materials are related to the different types of bonds they contain, their bond strengths in relation to intermolecular forces and the ways in which their bonds are arranged, recognising that the atoms themselves do not have these properties.

Details of the Science Content

Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.
These substances have only weak forces between the molecules (intermolecular forces).
It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.
The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points. These substances do not conduct electricity because the molecules do not have an overall electric charge.
Polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds. The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature. Substances that consist of giant covalent structures are solids with very high melting points. All of the atoms in these structures are
linked to other atoms by strong covalent bonds. These bonds must be overcome to melt or boil these substances. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures

Scientific, Practical and Mathematical Skills

WS 1.2

Use the idea that intermolecular forces are weak compared with covalent bonds to explain the bulk
properties of molecular substances.
Use ideas about energy transfers and the relative strength of chemical bonds and intermolecular forces to explain the different temperatures at which changes of state occur.
Recognise polymers from diagrams showing their bonding.
Recognise giant covalent structures from diagrams showing their bonding.
Use data to predict states of substances under given conditions.

Metallic Bonding

GCSE Science Subject Content

Explain chemical bonding in terms of electrostatic forces and the sharing of electrons..

Details of the Science Content

Metals consist of giant structures of atoms arranged in a regular pattern.
The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure. The sharing of delocalised electrons gives rise to strong metallic bonds. The bonding in metals may be represented in the following form:

Scientific, Practical and Mathematical Skills

MS 5b

Draw or complete diagrams to represent 2D and 3D forms including twodimensional representations of 3D structures.

Properties of Metals

GCSE Science Subject Content

Details of the Science Content

Metals have giant structures of atoms with strong metallic bonding. This means that most metals have high melting and boiling points.
The layers of atoms in a metal crystal can slide over each other. This means metals can be bent and shaped.
Pure metals are too soft for many uses and so are mixed with other metals to make alloys. The different sizes of atoms in an alloy distort the crystal structure, making alloys harder than pure metals.
Metals are good conductors of electricity because the delocalised electrons in the metal carry electrical charge through the metal.

Scientific, Practical and Mathematical Skills

WS 1.2

Magnetism and Electromagnetism

Magnets

GCSE Science Subject Content

Describe the attraction and repulsion between unlike and like poles for permanent magnets and describe the difference between permanent and induced magnets.

Details of the Science Content

The poles of a magnet are the places where the magnetic forces are strongest. When two magnets are brought close together they exert a force on each other. Attraction and repulsion between two magnetic poles are examples of non-contact force. A permanent magnet produces its own magnetic field. An induced magnet is a material that becomes a magnet when it is placed in a magnetic field. Induced magnetism always causes a force of attraction. When removed from the magnetic field an induced magnet loses most/all of its magnetism quickly.

Magnetic Fields

GCSE Science Subject Content

Describe the characteristics of the magnetic field of a magnet, showing how strength and direction
change from one point to another.

Details of the Science Content

The region around a magnet where a force acts on another magnet or on a magnetic material (iron, steel, cobalt and nickel) is called the magnetic field.
The force between a magnet and a magnetic material is always one of attraction.
The strength of the magnetic field depends on the distance from the magnet. The field is strongest at the poles of the magnet.
The direction of the magnetic field at any point is given by the direction of the force that would act on another north pole placed at that point.
The direction of a magnetic field line is from the north (seeking) pole of a magnet to the south (seeking) pole of the magnet.

Scientific, Practical and Mathematical Skills

WS 2.2

Draw the magnetic field pattern of a bar magnet and describe how to plot the magnetic field pattern using a compass.

The Earth’s Magnetism

GCSE Science Subject Content

Explain how the behaviour of a magnetic compass is related to evidence that the core of the Earth
must be magnetic.

Details of the Science Content

A magnetic compass contains a small bar magnet. The Earth has a magnetic field. The compass needle points in the direction of the Earth’s magnetic field.
The Earth’s magnetic field is probably caused by movements in the liquid, iron-rich part of the outer core of the Earth. The slow changes to the positions of the magnetic north and south poles, and the way that the field reverses its direction from time to time, show that the magnetism of the core is dynamic and not static. The intervals between reversals are not uniform. The last reversal happened about 800,000 years ago.

Scientific, Practical and Mathematical Skills

WS 1.3

Explain why the data needed to answer a scientific question, in a given context, may not be available because of matters of scale and complexity.

The Magnetic Effect of an Electric Current

GCSE Science Subject Content

Describe how to show that a current can create a magnetic effect and describe the directions of the
magnetic field around a conducting wire.

Recall that the strength of the field depends on the current and the distance from the conductor, and explain how solenoid arrangements can enhance the magnetic effect.

Details of the Science Content

When a current flows through a conducting wire a magnetic field is produced around the wire. The shape of the magnetic field can be seen as a series of concentric circles in a plane perpendicular to the wire. The direction of these field lines depends on the direction of the current.

The strength of the magnetic field depends on the current through the wire and the distance from the wire.
Shaping a wire to form a solenoid increases the strength of the magnetic field created by a current through the wire. The magnetic field inside a solenoid is strong and uniform.
The magnetic field around a solenoid has a similar shape to that of a bar magnet. Adding an iron core increases the magnetic field strength of a solenoid. An electromagnet is a solenoid with an iron core.

Scientific, Practical and Mathematical Skills

WS 1.2, 3.1

Draw the magnetic field pattern for a straight wire carrying a current (showing the direction of the field).

WS 1.2

Use the ‘right-hand grip rule’ to predict the direction of the field.

WS 3.1

Draw the magnetic field pattern for a solenoid carrying a current (showing the direction of the field).

WS 1.4

Compare the advantages and disadvantages of permanent and electromagnets for particular uses.

The Motor Effect (HT only)

GCSE Science Subject Content

Describe how a magnet and a current carrying conductor exert a force on one another and show that
Fleming’s left-hand rule represents the relative orientations of the force, the conductor and the magnetic field.

Apply the equation that links the force on a conductor to the magnetic flux density, the current and the
length of conductor to calculate the forces involved.

Details of the Science Content

When a conductor carrying a current is placed in a magnetic field the magnet producing the field and the conductor exert a force on each other. This is called the motor effect.
The direction of the force on the conductor is reversed if either the direction of the current or the direction of the magnetic field is reversed.

The size of the force on the conductor depends on:

• the magnetic flux density

• the current in the conductor

• the length of conductor in the magnetic field.

For a conductor at right angles to a magnetic field and carrying a current:

force = magnetic f lux density × current × length
[F = B I | ]
force, F, in newtons, N
magnetic flux density, B, in tesla, T
current, I, in amperes, A (amp is acceptable for ampere)
length, l, in metres, m

Scientific, Practical and Mathematical Skills

WS 1.2

Use Fleming’s lefthand rule to predict the direction of the force on a conductor.

MS 3c

Apply this equation, which is given on the Physics equations sheet.

WS 3.3

Carry out and represent mathematical and statistical analysis.

Electric Motors (HT only)

GCSE Science Subject Content

Explain how this force is used to cause rotation in electric motors.

Details of the Science Content

A simple electric motor consists of a rectangular coil of wire that is free to turn in the magnetic field of a permanent magnet. A commutator reverses the direction of the current every half turn, to allow the rotation to continue.

Scientific, Practical and Mathematical Skills

WS 1.2

Apply Fleming’s lefthand rule to a simple electric motor.

WS 1.4

Explain everyday and technological applications of science.

Force and Motion

Speed and Velocity

GCSE Science Subject Content

Explain the vector– scalar distinction as it applies to displacement, distance, velocity and speed. Recall typical speeds encountered in everyday experience for wind and sound,
and for walking, running, cycling and other transportation systems.

Details of the Science Content

Distance is how far an object moves. Distance does not involve direction. Distance is a scalar quantity.
Displacement includes both the distance an object moves, measured in a straight line from the start point to the finish point, and the direction of that straight line. Displacement is a vector quantity.
Speed does not involve direction.

Speed is a scalar quantity. The velocity of an object is its speed in a given direction. Velocity is a vector quantity. The speed of a moving object is rarely constant. When people walk, run or travel in a car their speed is constantly changing. The speed that a person can walk, run or cycle depends on many factors, including age, terrain, fitness and distance travelled. Typical mean values are:

• walking 1.5 m/s

• running 3 m/s

• cycling 6 m/s.

It is not only moving objects that have varying speed. The speed of sound and the speed of the wind also vary. A typical value for the speed of sound is 330 m/s.

Distance, Speed and Time

GCSE Science Subject Content

Make measurements of distances and times, calculate speeds, and make and use graphs of these to determine the speeds and accelerations involved.

Details of the Science Content

The distance travelled by an object moving at constant speed increases with time.

distance travelled = speed × time

s = v t

distance, s, in metres, m
speed, v, in metres per second, m/s
time, t, in seconds, s

If an object moves along a straight line, how far it is from a certain point can be represented by a distance–time graph.
The speed of an object can be calculated from the gradient of its distance–time graph. (HT only) If an object is accelerating, its speed at any particular time can be determined by drawing a tangent and measuring the gradient of the distance–time graph at that time.

Scientific, Practical and Mathematical Skills

MS 3b, 3c

Recall and apply this equation.

WS 4.5, MS 1c, 3b, 3c

Use ratios and proportional reasoning to convert units and to compute rates.

WS 1.2, 3.5, MS 4a, 4b, 4c, 4d, 4f

Relate changes and differences in motion to appropriate distance– time, and velocity–time graphs, and interpret lines, slopes and enclosed areas in such graphs.

MS 1a, 1c, 2f, 3c

Calculate average speed for non-uniform motion.

Circular motion (HT only)

GCSE Science Subject Content

Explain with examples that motion in a circular orbit involves constant speed but changing velocity (qualitative only).

Details of the Science Content

The velocity of an object is its speed in a given direction. Velocity is a vector quantity. When an object moves in a circle the direction of the object is continually changing. This means that an object moving in a circle at constant speed has a continually changing velocity.

Free Fall

GCSE Science Subject Content

Recall the acceleration in free fall and estimate the magnitudes of everyday accelerations

Details of the Science Content

Acceleration is the rate at which the velocity of an object changes. acceleration = change in velocity time taken

a = ∆ v t

acceleration, a, in metres per second squared, m/s² change in velocity, ∆v, in metres per second, m/s time, t, in seconds, s

An object that slows down (decelerates) has a negative acceleration. The acceleration of an object can be calculated from the gradient of a velocity–time graph. The distance travelled by an object (or displacement of an object) can be calculated from the area under a velocity–time graph.

(HT only) The following equation applies to uniform motion: f inal velocity 2 − initial velocity 2 = 2 × acceleration × distance

v ² − u² = 2 as final velocity, v, in metres per second, m/s initial velocity, u, in metres per second, m/s acceleration, a, in metres per second squared, m/s ² distance, s, in metres, m Near the Earth’s surface any object falling freely under gravity has an acceleration of about 9.8 m/s² .

An object falling through a fluid initially accelerates due to the force of gravity. Eventually the resultant force will be zero and the object will move at its terminal velocity.

Scientific, Practical and Mathematical Skills

WS 1.2, 3.3, MS 3b, 3c

Recall and apply this equation.

WS 1.2, 3.5, MS 4a, 4b, 4c, 4d, 4f, 5c

Relate changes and differences in motion to appropriate velocity–time graphs, and interpret lines and
slopes to determine acceleration.
(HT only) Interpret enclosed areas in such graphs to determine distance travelled (or displacement).
(HT only) Measure, when appropriate, the area under a velocity– time graph by counting squares.

WS 1.2, 3.3, MS 3c
(HT only)

Apply this equation, which is given on the Physics equation sheet.

Newton’s First Law

GCSE Science Subject Content

Apply Newton’s First Law to explain the motion of objects moving with uniform velocity and also objects where the speed and/or direction change.

Details of the Science Content

Newton’s First Law:
If the resultant force acting on an object is zero and:

• the object is stationary, the object remains stationary

• the object is moving, the object continues to move at the same speed and in the same direction. So the object continues to move at the same velocity.

Circular motion (HT only)

GCSE Science Subject Content

Apply Newton’s Second Law in calculations relating forces, masses and accelerations.

(HT only) Explain that inertial mass is a measure of how difficult it is to change the velocity of an object and that it is defined as the ratio of force over acceleration.

Details of the Science Content

Newton’s Second Law: The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object. resultant force = mass × acceleration F = m a force, F, in newtons, N mass, m, in kilograms, kg acceleration, a, in metres per second squared, m/s²

(HT only) The tendency of objects to continue in their state of rest or of uniform motion is called inertia.
Inertial mass is a measure of how difficult it is to change the velocity of an object. Inertial mass is defined by the ratio of force over acceleration.

Scientific, Practical and Mathematical Skills

MS 3a

Recognise and be able to use the symbol:

• for proportionality, α

• that indicates an approximate value or answer, ̴
WS 1.2, 3.3, MS 3c

Recall and apply this equation.

Newton’s Third Law

GCSE Science Subject Content

Recall Newton’s Third Law and apply it to examples of equilibrium situations

Details of the Science Content

Newton’s Third Law: Whenever two objects interact, the forces they exert on each other are equal and opposite.

Momentum (HT only)

GCSE Science Subject Content

Define momentum and describe examples of momentum in collisions.

Details of the Science Content

Momentum is a property of moving objects. Momentum is defined by the equation:
momentum = mass × velocity
p = m v
momentum, p, in kilograms metre per second, kg m/s

mass, m, in kilograms, kg
velocity, v, in metres per second, m/s

In a closed system, the total momentum before an event is equal to the total momentum after
the event. This is called conservation of momentum.

Scientific, Practical and Mathematical Skills

WS 1.2, 3.3, MS 3c

Recall and apply this equation.

WS 1.2 Use the concept of momentum as a model to analyse an event such as a collision.

Kinetic Energy

GCSE Science Subject Content

Calculate the amounts of energy associated with a moving body. Describe all the changes involved in
the way energy is stored when a system changes for common situations: a moving object hitting an obstacle, or an object being accelerated by a constant force.

Details of the Science Content

The kinetic energy of a moving object depends
on the mass and the velocity of the object.
kinetic energy = 0.5 × mass × (speed)²
Ek = 1/2 m v²
kinetic energy, Ek , in joules, J mass, m, in kilograms, kg speed, v, in metres per second, m/s

Scientific, Practical and Mathematical Skills

WS 1.2, 3.3, MS 3c

Recall and apply this equation.

Stopping Distances

GCSE Science Subject Content

Explain the factors which affect the distance required for road transport vehicles to come to rest in emergencies and the implications for safety

Explain the dangers caused by large decelerations. Describe all the changes involved in the way energy is stored when a system changes, for common situations, like a vehicle slowing down.

Details of the Science Content

The stopping distance of a vehicle is the sum of the distance the vehicle travels during the driver’s reaction time (thinking distance) and the distance it travels under the braking force (braking distance).
For a given braking force the greater the speed of the vehicle, the greater the stopping distance. The braking distance of a vehicle can be affected by wet or icy weather and poor condition of the vehicle’s brakes or tyres. A driver’s reaction time (see The human nervous system (page 41)) can be affected by tiredness, drugs and alcohol. Distractions may also affect a driver’s ability to react.

When a force is applied to the brakes of a vehicle, work done by the friction force between the brakes and the wheel reduces the kinetic energy of the vehicle and the temperature of the brakes increases.
The greater the speed of a vehicle the greater the braking force needed to stop the vehicle in a certain distance. The greater the braking force the greater the deceleration of the vehicle. Large decelerations may lead to brakes overheating and/or loss of control.

Scientific, Practical and Mathematical Skills

WS 3.6

Analyse a given situation to explain why braking could be affected.

WS 1.5

Discuss the implications for safety.

WS 3.5, MS 4a

Interpret graphs relating speed to stopping distance for different types of vehicles.

WS 1.5, 2.2, MS 1a, 1c

Evaluate the effect of various factors on thinking distance based on given data.

WS 1.5, MS 1d (HT only)

Estimate the forces involved in typical situations on a public road.

Electricity

Electric Current

GCSE Science Subject Content

Recall that current is a rate of flow of charge, that for a charge to flow a source of potential difference
and a closed circuit are needed and that a current has the same value at any point in a single closed loop. Recall and use the relationship between quantity of charge, current and time.

Details of the Science Content

For electrical charge to flow through a closed circuit the circuit must include a source of potential difference.
Electric current is a flow of electrical charge. The size of the electric current is the rate of flow of electrical charge.
charge f low = current × time
Q = I t
charge flow, Q, in coulombs, C current, I, in amperes, A (amp is acceptable for ampere)
time, t, in seconds, s
A current has the same value at any point in a single closed loop.

Scientific, Practical and Mathematical Skills

WS 3.3, MS 3b, 3c

Recall and apply this equation.

Current, Resistance and Potential Difference

GCSE Science Subject Content

Recall that current (I) depends on both resistance (R) and potential difference (V) and the units in which these are measured; recall and apply the relationship between I, R and V, and explain that for some resistors the value of R remains constant.

Explain that in other types of resistor the value of R can change as the current changes; explain the design and use of circuits to explore such effects – including lamps, diodes, thermistors and light-dependent resistors (LDRs).

Details of the Science Content

The current through a component depends on both the resistance of the component and the potential difference across the component. The greater the resistance of the component the smaller the current for a given potential difference across the component.
potential di f f erence = current × resistance
V = I R
potential difference, V, in volts, V current, I, in amperes, A (amp is acceptable for ampere)
resistance, R, in ohms, Ω
The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the conductor.
This means that the resistance remains constant as the current changes.

The resistance of components such as lamps, diodes, thermistors and LDRs is not constant; it changes with the current through the component.
The resistance of a filament lamp increases as the temperature of the filament increases. The current through a diode flows in one direction only. The diode has a very high resistance in the reverse direction.
The resistance of a thermistor decreases as the temperature increases. The resistance of an LDR decreases as light intensity increases

Scientific, Practical and Mathematical Skills

WS 3.3, MS 3c

Recall and apply this equation.

WS 1.2, 3.5, MS 4c, 4d, 4e

Use graphs to determine whether circuit components are linear or non-linear and relate the curves produced to the function and properties of the component.

Series and Parallel Circuits

GCSE Science Subject Content

Describe the difference between series and parallel circuits; explain why, if two resistors are
in series, the net resistance is increased, whereas with two in parallel the net resistance is decreased (qualitative explanation only).Calculate the currents, potential differences and resistances in direct current (dc) series circuits, and explain the design and use of such circuits for
measurement and testing purposes.

Details of the Science Content

There are two ways of joining electrical components: in series and in parallel. Some circuits include both series and parallel parts. For components connected in series:

• there is the same current through each component

• the total potential difference of the power supply is shared between the components

• the total resistance of two components is the sum of the resistance of each component.

Rtotal = R1 + R2
resistance, R, in ohms, Ω

For components connected in parallel:

• the potential difference across each component is the same

• the total current through the whole circuit is the sum of the currents through the separate components

• the total resistance of two resistors is less than the resistance of the smallest individual resistor.

Scientific, Practical and Mathematical Skills

WS 3.3, MS 1c, 3b, 3c, 3d

Solve problems for circuits which include resistors in series using the concept of equivalent resistance.

WS 3.3, MS 1c, 3b, 3c, 3d

Calculate the currents, potential differences and resistances in dc series circuits. Calculating the total resistance of two resistors joined in parallel is not required.

Circuit Elements

GCSE Science Subject Content

Represent in dc series circuits with the conventions of positive and negative terminals, the symbols that represent common circuit elements, including diodes, LDRs and thermistors.

Details of the Science Content

Circuit diagrams use standard symbols.

Direct and Alternating Currents

GCSE Science Subject Content

Recall that the domestic supply in the UK is ac, at 50Hz and about 230 volts; explain the difference between direct and alternating voltage.

Details of the Science Content

Cells and batteries supply current that always passes in the same direction. This is called direct current (dc).
An alternating current (ac) is one that changes direction. In the UK ac supply the current changes direction 50 times per second.

Mains Cables

GCSE Science Subject Content

Recall the differences in function between the live, neutral and earth mains wires, and the potential differences between these wires;hence explain that a live wire may be dangerous even when a switch in a mains circuit is open, and explain the dangers of providing any connection between the live wire and earth.

Details of the Science Content

Most electrical appliances are connected to the mains using three-core cable. The insulation covering each wire is colour coded for easy identification.

• Live wire – brown

• Neutral wire – blue

• Earth wire – green and yellow stripes

The live wire carries the alternating potential difference from the supply. The neutral wire completes the circuit. The earth wire is a safety wire to stop the appliance becoming live.
The potential difference between the live wire and earth (0 V) is about 230 V. The neutral wire is at or close to earth potential (0 V). The earth wire is at 0 V; it carries a current only if there is a fault.
Our bodies are at earth potential (0 V). Touching the live wire produces a large potential difference across our body. This causes a current to flow through our body, resulting in an electric shock.

Scientific, Practical and Mathematical Skills

WS 1.5 Identify an electrical hazard in a given context.

Power

GCSE Science Subject Content

Explain, with reference to examples, the definition of power as the rate at which energy is transferred.

Details of the Science Content

Power is defined as the rate at which energy is transferred or the rate at which work is done.
power = energy transferred / time
P = E/t
power = work done/time
P = W/t
power, P, in watts, W energy transferred, E, in joules, J time, t, in seconds, s work done, W, in joules, J
An energy transfer of 1 joule per second is equal to a power of 1 watt.

The power of an electrical device is related to the potential difference across it and the current through it by the equation: power = potential difference × current P = V I power = current² × resistance P = I R power, P, in watts, W potential difference, V, in volts, V current, I, in amperes, A (amp is acceptable for ampere) resistance, R, in ohms, Ω

Scientific, Practical and Mathematical Skills

WS 1.2, 3.3,MS 3b, 3c

Recall and apply both of these equations.

WS 1.2, 3.3, MS 3b, 3c

Recall and apply both of these equations.

Power and Domestic Electric Appliances

GCSE Science Subject Content

Describe how, in different domestic devices, energy is transferred from batteries and the ac mains to the energy of motors or of heating devices. Describe all the changes involved in the way energy is stored when a system changes, for common situations: bringing water to a boil in an electric kettle.
Describe, with examples, the relationship between the power ratings for domestic electrical appliances and the changes in stored energy when they are in use.
Describe and calculate the changes in energy involved when a system is changed by work done when a current flows.

Details of the Science Content

Everyday electrical appliances are designed to bring about energy transfers. The amount of energy an appliance transfers depends on how long the appliance is switched on for and the power of the appliance.
Work is done when charge flows in a circuit. The amount of energy transferred can be calculated using the equations:

energy transferred = power × time
E = P t

energy transferred = charge flow × potential difference

E = Q V
energy transferred, E, in joules, J power, P, in watts, W time, t, in seconds, s charge flow, Q, in coulombs, C potential difference, V, in volts, V

Scientific, Practical and Mathematical Skills

WS 1.4

Explain everyday and technological applications of science.

WS 1.2, 3.3, MS 3c

Recall and apply both of these equations

The National Grid

GCSE Science Subject Content

Recall that, in the national grid, electrical power is transferred at high voltages from power stations and then transferred at lower voltages in each locality for domestic use; and explain how this system is an efficient way to transfer energy.

Details of the Science Content

The National Grid is a system of cables and transformers linking power stations to consumers.
Electrical power is transferred from power stations to consumers using the National Grid.
Step-up transformers are used to increase the potential difference from the power station to the transmission cables then step-down transformers are used to decrease the potential difference to a much lower value for domestic use.
(HT only) Students should be able to select and use the equation:
potential difference across primary coil x current in primary coil = potential difference across secondary coil x current in secondary coil
as given on the equation sheet.

Scientific, Practical and Mathematical Skills

WS 1.4

Explain everyday and technological applications of science. Detailed knowledge of the structure of a transformer is not required.

Reactions of Acids

GCSE Science Subject Content

Recall that acids react with some metals and with carbonates, and write equations predicting products from given reactants. Describe tests to identify selected gases including hydrogen and carbon dioxide.

Details of the Science Content

Scientific, Practical and Mathematical Skills

WS 1.2 (HT only)

Explain, in terms of gain or loss of electrons, that the reactions of metals with acids are redox reactions (see Atoms into ions and ions into atoms (page 134)).

WS 4.1 (HT only) Identify which species are oxidised and which are reduced in given chemical reactions.

Making Salts

GCSE Science Subject Content

Describe neutralisation as acid reacting with alkali to form a salt plus water.
Describe, explain and exemplify the processes of filtration and crystallisation. Suggest suitable
purification techniques given information about the substances involved.

Details of the Science Content

Acids are neutralised by alkalis (eg soluble metal hydroxides) and bases (eg insoluble metal hydroxides and metal oxides) to produce salts and water, and by metal carbonates to produce salts, water and carbon dioxide.
The particular salt produced in any reaction between an acid and a base or alkali depends on:

• the acid used (hydrochloric acid produces chlorides, nitric acid produces nitrates and sulfuric acid produces sulfates)

• the positive ions in the base, alkali or carbonate.
Soluble salts can be made from acids by reacting them with solid insoluble substances such as metals, metal oxides, hydroxides or carbonates.

The solid is added to the acid until no more reacts, and the excess solid is filtered off to produce a solution of the salt. Salt solutions can be crystallised to produce solid salts.

Scientific, Practical and Mathematical Skills

WS 1.2

Predict products from given reactants. Use the formulae of common ions to deduce the formulae of salts.

Energy Changes and Reactions

GCSE Science Subject Content

Distinguish between endothermic and exothermic reactions on the basis of the temperature change of the surroundings.

Details of the Science Content

When chemical reactions occur, energy is transferred to or from the surroundings. Energy is conserved in chemical reactions. The total amount of energy in the reaction mixture and its surroundings at the end of a chemical reaction is the same as it was at the start. An exothermic reaction is one that gives out energy. This heats up the reaction mixture. Energy then transfers to the surroundings as the reaction mixture then cools. Neutralisation of an acid with an alkali is an example of an exothermic reaction. An endothermic reaction is one that that takes in energy. This cools the reaction mixture. Energy then transfers from the surroundings as the reaction mixture then warms up again. The reaction of citric acid and sodium hydrogen carbonate is an example of an endothermic reaction.

Scientific, Practical and Mathematical Skills

WS 1.2

Identify examples of exothermic and endothermic reactions based on the temperature change of the reaction mixture.

The PH Scale and Neutralisation

GCSE Science Subject Content

Recall that acids form hydrogen ions when they dissolve in water and solutions of alkalis contain hydroxide ions. (HT only) Use the formulae of common ions to write balanced ionic equations.
Recall that relative acidity and alkalinity are measured by pH.
Recognise that aqueous neutralisation reactions can be generalised to hydrogen ions reacting with hydroxide ions to form water.

Details of the Science Content

Acids produce hydrogen ions (H+ ) in aqueous solutions. Aqueous solutions of alkalis contain hydroxide ions (OH–).
The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution and can be measured using universal indicator or a pH probe.
A solution with pH 7 is neutral. Aqueous solutions of acids have pH values of less than 7 and aqueous solutions of alkalis have pH values greater than 7.
In neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water.

Scientific, Practical and Mathematical Skills

WS 1.2

Write an ionic equation to represent neutralisation.

WS 2.3

Describe the use of universal indicator or a wide range indicator to measure the approximate pH of a solution.

WS 3.2

Use the pH scale to identify acidic or alkaline solutions.

Strong and Weak Acids (HT only)

GCSE Science Subject Content

Use and explain the terms dilute and concentrated (amount of substance) and weak and strong
(degree of ionisation) in relation to acids.
Recall that as hydrogen ion concentration increases by a factor of ten the pH value of a solution decreases by a factor of one.
Describe neutrality and relative acidity and alkalinity in terms of the effect of the concentration of
hydrogen ions on the numerical value of pH (whole numbers only).

Details of the Science Content

A strong acid is completely ionised in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids. A weak acid is only partially ionised in aqueous solution. Examples of weak acids are ethanoic, citric and carbonic acids. For a given concentration of aqueous solutions, the stronger an acid, the lower the pH.

Factors that Affect Reaction Rates

GCSE Science Subject Content

Describe the effect of changes in temperature, concentration, pressure, and surface area on rate of
reaction.
Suggest practical methods for determining the rate of a given reaction.

Details of the Science Content

The rate of a chemical reaction can be found by measuring the quantity of a reactant used or the quantity of product formed over time:

mean rate of reaction = quantity of reactant used/ time taken

mean rate of reaction = quantity of product formed/ time taken

The quantity of reactant or product can be measured by the mass in grams, by a volume in cm³ ((HT only) or by an amount in moles). The units of rate of reaction may be given as g/s, cm³ /s ((HT only) or mol/s). The rate of a chemical reaction can be determined by measuring:

• the loss in mass of a reactant’s mixture

• the volume of gas produced

• the time for a solution to become opaque or coloured.

Scientific, Practical and Mathematical Skills

WS 3.3, MS 1a, 1c

Calculate the mean rate of a reaction from given information about the quantity of a reactant used or the quantity of a product formed and the time taken.

WS 3.5, MS 4a, 4b, 4c

Draw, and interpret, graphs showing the quantity of product formed or quantity of reactant used up against time to compare or determine rates of reaction.

WS 3.3, MS 4e

Draw tangents to the curves on these graphs and use the gradient of the tangent as a measure of the rate of reaction.

WS 3.3, MS 4d, 4e (HT only)

Calculate the gradient of a tangent to the curve on these graphs as a measure of rate of reaction at a specific time.

The Effect of Surface Area on Rates of Reaction

GCSE Science Subject Content

Explain the effects on rates of reaction of changes in the size of the pieces of a reacting solid in terms of surface area to volume ratio.

Details of the Science Content

Breaking up a solid reactant into smaller pieces increases the surface area that can be in contact with any solution with which it reacts.
Increasing the ratio of surface area to volume increases the rate of reaction for a given mass of a solid reactant.

Scientific, Practical and Mathematical Skills

MS 1c

Use proportionality when comparing factors affecting rate of reaction.

MS 5c

Calculate surface areas and volumes of cubes.

The Effect of Temperature, Concentration and Pressure on Rates of Reaction

GCSE Science Subject Content

Explain the effects on rates of reaction of changes in temperature, concentration and pressure in terms of the frequency and energy of collision between particles.

Details of the Science Content

According to collision theory, chemical reactions can occur only when reacting particles collide with each other and with sufficient energy. The minimum amount of energy that particles must have to react is called the activation energy.
Increasing the concentration of reactants in solution, the pressure of reacting gases and the surface area of solid reactants increases the frequency of collisions and so increases the rate of reaction.
Increasing the temperature increases the frequency of collisions and makes the collisions more energetic, and so increases the rate of reaction.

Scientific, Practical and Mathematical Skills

WS 1.2

Predict and explain the effects of changing conditions on the rate of a reaction.

Activation Energy

GCSE Science Subject Content

Explain activation energy as the energy needed for a reaction to occur.
Draw and label a reaction profile for an exothermic and an endothermic reaction, identifying activation
energy.

Details of the Science Content

Chemical reactions can occur only when reacting particles collide with each other and with sufficient energy. The minimum amount of energy that particles must have to react is called the activation energy.
Reaction profiles can be used to show the relative energies of reactants and products, the activation energy and the overall energy change of a reaction.

Scientific, Practical and Mathematical Skills

WS 3.2, 3.5, MS 4a

Interpret reaction profiles, including using them to identify reactions as exothermic or endothermic.

Bond Breaking and Bond Forming (HT only)

GCSE Science Subject Content

Calculate energy changes in a chemical reaction by considering bond making and bond breaking energies.

Details of the Science Content

During a chemical reaction:

• energy must be supplied to break bonds in the reactants

• energy is given out when bonds in the products are formed.

The energy needed to break bonds and the energy given out when bonds are formed can be calculated from bond energies. The difference between the sum of the energy needed to break bonds in the reactants and the sum of the energy given out when bonds in the products are formed is the overall energy change of the reaction.
In an exothermic reaction, the energy given out from forming new bonds is greater than the energy needed to break existing bonds.
In an endothermic reaction, the energy needed to break existing bonds is greater than the energy given out from forming new bonds.

Scientific, Practical and Mathematical Skills

WS 3.3, MS 1a

Use arithmetic computation when calculating energy changes.

WS 1.2, 3.3, MS 1a, 4a

Calculate the energy transferred in chemical reactions between simple molecules in the gas state using bond energies supplied.

Catalysts

GCSE Science Subject Content

Describe the characteristics of catalysts and their effect on rates of reaction.
Identify catalysts in reactions.
Explain catalytic action in terms of activation energy.

Details of the Science Content

Catalysts change the rate of chemical reactions but are not used up during the reaction. Different reactions need different catalysts.
Knowledge of the names of catalysts other than those specified in the subject content is not required.

Scientific, Practical and Mathematical Skills

WS 3.5

Identify catalysts in reactions from their effect on the rate of reaction and because they are not included in the chemical equation for the reaction.

WS 1.2

Use reaction profiles to explain catalytic action.

Enzymes

GCSE Science Subject Content

Recall that enzymes act as catalysts in biological systems. Explain the mechanism of enzyme action
including the active site, enzyme specificity and factors affecting the rate of enzymatic reaction.

Details of the Science Content

Enzymes are important as biological catalysts which allow all the reactions in cells to occur.
Enzymes are large protein molecules. The shape of an enzyme is vital for its function.
Each enzyme has an active site with a unique shape to bind a specific substrate molecule.
High temperatures and extremes of pH denature the enzyme, changing the shape of the active site. The ‘lock and key’ model is a simplified model of enzyme action.
Different enzymes work fastest at different temperatures and pH values.

Scientific, Practical and Mathematical Skills

WS 3.3, 3.5, MS 1a,
1c, 1d
Carry out rate calculations for chemical reactions and make estimates of simple calculations without using a calculator.

Reversable Reactions

GCSE Science Subject Content

Recall that some reactions may be reversed by altering the reaction conditions.

Details of the Science Content

In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called reversible reactions and are represented:
A + B = C + D
The direction of reversible reactions can be changed by changing the temperature. Examples include the effect of changing the temperature on the decomposition of ammonium chloride and of hydrated copper(II) sulfate.

Dynamic Equilibrium

GCSE Science Subject Content

Recall that dynamic equilibrium occurs when the rates of forward and reverse reactions are equal.

Details of the Science Content

When a reversible reaction occurs in apparatus which prevents the escape of reactants and products, equilibrium is reached when the forward and reverse reactions occur at exactly the same rate.

Factors Affecting the Position of Equilibrium (HT only)

GCSE Science Subject Content

Predict the effect of changing reaction conditions on equilibrium position.

Predict the effect of changing concentration on equilibrium position and suggest appropriate conditions to produce a particular product.

Predict the effect of changing temperature on equilibrium position and suggest appropriate conditions to produce a particular product.

Predict the effect of changing pressure on equilibrium position and suggest appropriate conditions
to produce a particular product.

Details of the Science Content

The relative amounts of all the reactants and products at equilibrium depend on the conditions of the reaction.
If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change.

If the concentration of one of the reactants or products is changed, the system is no longer at equilibrium and the concentrations of all the substances change until equilibrium is reached again.
If the concentration of a reactant is increased, more products form until equilibrium is reached again.
If the concentration of a product is decreased, more reactants react until equilibrium is reached again.

If the temperature of a system at equilibrium is increased:

• the relative amount of products at equilibrium increases for an endothermic reaction

• the relative amount of products at equilibrium decreases for an exothermic reaction.

If the temperature of a system at equilibrium is decreased:

• the relative amount of products at equilibrium decreases for an endothermic reaction

• the relative amount of products at equilibrium increases for an exothermic reaction.

For gaseous reactions at equilibrium:

• an increase in pressure causes the equilibrium position to shift towards the side with the smaller number of molecules, as shown by the symbol equation for that reaction

• a decrease in pressure causes the equilibrium position to shift towards the side with the larger number of molecules, as shown by the symbol equation for that reaction.

Scientific, Practical and Mathematical Skills

WS 1.2

Apply Le Châtelier’s principle to make qualitative predictions about the effect of changes on systems at equilibrium when given appropriate information.

WS 3.5
Interpret appropriate given data to predict the effect of a change in concentration of a reactant or product on given reactions at equilibrium.

WS 1.2

Apply the idea that if a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction.

Atoms into Ions and Ions into Atoms

A Reactivity Series for Metals

GCSE Science Subject Content

Explain how the reactivity of metals with water or dilute acids is related to the tendency of the metal to form its positive ion.

Details of the Science Content

When metals react with other substances the metal atoms form positive ions. Metals can be arranged in order of their reactivity in a
reactivity series. The metals potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper can be put in order of their reactivity from their reactions with water and dilute acids.
The non-metals hydrogen and carbon are often included in the reactivity series.
A more reactive metal can displace a less reactive metal from a compound.
The reactions of metals with water and acids are limited to room temperature and do not include reactions with steam.

Scientific, Practical and Mathematical Skills

WS 3.8
Recall and describe the reactions, if any, of potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper with water or dilute acids.
WS 3.5
Deduce an order of reactivity of metals based on experimental results.
WS 1.2
(HT only) Write ionic equations for displacement reactions

Electrolysis

GCSE Science Subject Content

Describe electrolysis in terms of the ions present and reactions at the electrodes.
Recall that metals (or hydrogen) are formed at the cathode and non-metals are formed at the anode in electrolysis using inert electrodes.

Details of the Science Content

When an ionic compound is melted or dissolved in water, the ions are free to move about within the liquid or solution. These liquids and solutions are able to conduct electricity and are called electrolytes. Passing an electric current through electrolytes causes the ions to move to the electrodes. Positively charged ions move to the negative electrode (the cathode), and negatively charged ions move to the positive electrode (the anode). Ions are discharged at the electrodes producing elements. This process is called electrolysis. When a simple ionic compound is electrolysed in the molten state using inert electrodes, the metal is produced at the cathode and the nonmetal is produced at the anode.

Scientific, Practical and Mathematical Skills

WS 1.2

Predict the products of electrolysis of binary ionic compounds in the molten state. (HT only) Write half equations for the reactions occurring at the electrodes during electrolysis. Students may be required to complete and balance supplied half equations.

Electrolysis of Aqueous Solutions

GCSE Science Subject Content

Describe competing reactions in the electrolysis of aqueous solutions of ionic compounds in terms of the different species present.

Details of the Science Content

The ions discharged when an aqueous solution is electrolysed using inert electrodes depend on the relative reactivity of the elements involved.
At the negative electrode (cathode), hydrogen is produced if the metal is more reactive than hydrogen.
At the positive electrode (anode), oxygen is produced unless the solution contains halide ions when the halogen is produced.
This happens because in the aqueous solution water molecules break down producing hydrogen ions and hydroxide ions that are discharged.

Scientific, Practical and Mathematical Skills

WS 1.2 (HT only)

Write half equations for the reactions occurring at the electrodes during electrolysis. Students may be required to complete and balance supplied half equations

Tests for Gases

GCSE Science Subject Content

Describe tests to identify selected gases including oxygen, hydrogen and chlorine.

Details of the Science Content

The test for hydrogen uses a burning splint held at the open end of a test tube of the gas.
The test for oxygen uses a glowing splint inserted into a test tube of the gas.
The test for chlorine uses damp litmus paper put into chlorine gas.

Scientific, Practical and Mathematical Skills

WS 3.5

Interpret the observations from gas tests.

Electron Transfer Reactions (HT only)

GCSE Science Subject Content

Explain reduction and oxidation in terms of gain or loss of electrons, identifying which species are
oxidised and which are reduced.

Details of the Science Content

Oxidation is the loss of electrons and reduction is the gain of electrons.
During electrolysis, at the cathode (negative electrode), positively charged ions gain electrons and so the reactions are reductions.
At the anode (positive electrode), negatively charged ions lose electrons and so the reactions are oxidations

Scientific, Practical and Mathematical Skills

WS 4.1

Identify, in a given reaction, symbol equation or half equation, which species are oxidised and which are reduced.

Carbon Chemistry

Bonding and Structure in Forms of Carbon

GCSE Science Subject Content

Explain the properties of diamond, graphite, fullerenes and graphene in terms of their structures and
bonding.

Details of the Science Content

Diamond is very hard, has a very high melting point and does not conduct electricity. In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure.
Graphite is soft, has a high melting point and conducts electricity.
In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings. There are no covalent bonds between layers. One electron from each carbon is delocalised.
Graphene is a single layer of graphite and so is one atom thick. It has properties that make it useful in electronics and composites.
Fullerenes are molecules of carbon atoms with hollow shapes. The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms. The first fullerene to be discovered was buckminsterfullerene (C60), which has a spherical shape.
Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios. Their properties make them useful for nanotechnology, electronics and materials.

Scientific, Practical and Mathematical Skills

MS 5b

Visualise and represent 2D and 3D forms including twodimensional representations of 3D objects. WS 1.4

Give examples of the uses of diamond, graphite and fullerenes, including carbon nanotubes.

Hydrocarbons in Crude Oil

GCSE Science Subject Content

Recall that crude oil is a main source of hydrocarbons and is a feedstock for the petrochemical industry.
Recognise that crude oil is a finite resource. Recall that carbon can form four covalent bonds.
Explain that the vast array of natural and synthetic organic compounds occur due to the ability of carbon to form families of similar compounds, chains and rings.
Describe the fractions as largely a mixture of compounds of formula CnH2n+2 which are members of the alkane homologous series.

Details of the Science Content

Crude oil is a finite resource found in rocks. Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud.
Crude oil is a mixture of a very large number of compounds. Most of the compounds in crude oil are hydrocarbons, which are molecules made up of hydrogen and carbon atoms only.
Alkane molecules can be represented in the following forms:

C2H6 .

Knowledge of the names of specific alkanes other than methane, ethane, propane and butane is not required.

Scientific, Practical and Mathematical Skills

WS 1.2, MS 5b

Recognise substances as alkanes given their formulae.

Fractional Distillation of Crude Oil

GCSE Science Subject Content

Describe and explain the separation of crude oil by fractional distillation.
Describe, explain and exemplify the processes of fractional distillation.
Explain how modern life is crucially dependent upon hydrocarbons.

Details of the Science Content

Some properties of hydrocarbons depend on the size of their molecules, including:

• boiling point

• viscosity, and

• flammability.

These properties influence how hydrocarbons are separated and how they are used as fuels.
Knowledge of trends in properties of hydrocarbons is limited to boiling point, viscosity and flammability.
The many hydrocarbons in crude oil may be separated into fractions, each of which contains molecules with a similar number of carbon atoms, by fractional distillation.
The fractions can be processed to produce fuels and feedstock for the petrochemical industry.
Many of the fuels on which our modern lifestyle depends such as petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases, are produced from crude oil. Knowledge of the names of other specific fractions or fuels is not required.
The combustion of hydrocarbon fuels releases energy. During combustion, the carbon and hydrogen in the fuels are oxidised. The complete combustion of a hydrocarbon produces carbon dioxide and water.
Many useful materials on which modern life depends are produced by the petrochemical industry. These include solvents, lubricants, polymers and detergents.

Scientific, Practical and Mathematical Skills

WS 1.2
Write balanced equations for the complete combustion of hydrocarbons with a given formula. Relate trends in the hydrocarbons to molecular size using ideas in Covalent bonding (page 101).

Cracking Hydrocarbons

GCSE Science Subject Content

Describe the production of materials that are more useful by cracking.

Details of the Science Content

Hydrocarbons can be broken down to produce smaller, more useful molecules by catalytic cracking or by steam cracking.
The products of cracking include alkanes and another type of hydrocarbon called alkenes.
Recall of the formulae or names of individual alkenes, other than ethene, is not required.
There is a high demand for fuels with small molecules and so some of the products of cracking are useful as fuels.
Alkenes are used to produce polymers and as starting materials for the production of many other chemicals. Small ethene molecules polymerise to produce long-chain molecules of poly(ethene) (see also Covalent bonding (page 101)).

Scientific, Practical and Mathematical Skills

WS 1.2

Balance chemical equations as examples of cracking given the formulae of the reactants and products.

Resources of Materials and Energy

Metal Extraction by Reduction of Oxides

GCSE Science Subject Content

Explain reduction and oxidation in terms of loss or gain of oxygen, identifying which species are oxidised and which are reduced.
Explain, using the position of carbon in the reactivity series, the principles of industrial processes
used to extract metals, including extraction of a non-ferrous metal

Details of the Science Content

Metals react with oxygen to produce metal oxides. These are oxidation reactions. Reduction involves the loss of oxygen.
Unreactive metals such as gold are found in the Earth as the metal itself but most metals are found as compounds that require chemical reactions to extract the metal.
Knowledge and understanding are limited to the reduction of oxides using carbon.
Metals less reactive than carbon can be extracted from their oxides by reduction with carbon.
Knowledge of the details of processes used in the extraction of metals is not required.

Scientific, Practical and Mathematical Skills

WS 1.2

Identify the substances which are oxidised or reduced in terms of gain or loss of oxygen.

WS 1.4

Explain in terms of the reactivity series why some metals are extracted with carbon and others by electrolysis. Interpret or evaluate specific metal extraction processes when given appropriate information.

Metal Extraction by Electrolysis

GCSE Science Subject Content

Explain why and how electrolysis is used to extract some metals from their ores.

Details of the Science Content

Metals can be extracted from molten compounds using electrolysis. Electrolysis is used if the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon. Large amounts of energy are used in the extraction process to melt the compounds and to produce the electrical current.
Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite using positive electrodes (anodes) made of carbon. The anodes have to be replaced from time to time

Scientific, Practical and Mathematical Skills

WS 1.4

Explain technological applications of science, including the use of cryolite for the extraction of aluminium and the need to replace the anodes.

Metal Extraction by Biological Methods (HT only)

GCSE Science Subject Content

Evaluate alternative biological methods of metal extraction (bacterial and phytoextraction).

Details of the Science Content

Copper ores are becoming scarce and new ways of extracting copper from low-grade ores include phytomining and bioleaching. These methods avoid traditional mining methods of digging, moving and disposing of large amounts of rock. Phytomining uses plants to absorb metal compounds. The plants are harvested and then burned to produce ash that contains metal compounds. Bioleaching uses bacteria to produce leachate solutions that contain metal compounds. The metal compounds can be processed to obtain the metal. For example, copper can be obtained from solutions of copper compounds by displacement using scrap iron or by electrolysis.

Scientific, Practical and Mathematical Skills

WS 1.4

Evaluate environmental implications of the applications of science.

Energy Resources

GCSE Science Subject Content

Describe the main energy resources available for use on Earth (including fossil fuels, nuclear fuel, biofuel, wind, hydroelectricity, the tides and the Sun); compare the ways in which they are used and distinguish between renewable and non-renewable resources.

Details of the Science Content

Non-renewable resources of energy include:

• coal

• crude oil

• natural gas

• nuclear fuel.

A renewable energy resource is one that is being (or can be) replenished as it is used.
Examples include:

• plants that provide biofuel

• wind turbines

• hydroelectricity

• tidal barrages or undersea turbines

• solar panels that produce electricity or
heat water.

Scientific, Practical and Mathematical Skills

WS 1.4

Explain technological applications of science. Explain patterns and trends in given data about the use of energy resources. Evaluate the use of different energy resources, taking into account reliability, cost and impact on the environment.

WS 4.4, MS 1c, 2c, 4a

Interpret data with energy quantities given, using the prefixes kilo, mega, giga and tera.

Energy Conservation and Dissipation

GCSE Science Subject Content

Describe, with examples, where there are energy transfers in a system and where there is no net change to the total energy of a closed system (qualitative only).
Describe, with examples, how in all system changes, energy is dissipated so that it is stored in less useful ways.

Details of the Science Content

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.
Whenever there are energy transfers in a system only part of the energy is usefully transferred. The rest of the energy is dissipated so that it is stored in less useful ways. This energy is often described as being ‘wasted’.

Scientific, Practical and Mathematical Skills

WS 3.3, MS 1a, 1c, 3c

Make calculations of the energy changes associated with changes in a system, recalling or selecting the relevant equations for mechanical, electrical and thermal processes; thereby express in quantitative form and on a common scale the overall redistribution of energy in the system.

Preventing Unwanted Energy Transfers

GCSE Science Subject Content

Explain ways of reducing unwanted energy transfer, eg through lubrication and thermal insulation;
describe the effects, on the rate of cooling of a building, of the thickness and thermal conductivity of its walls (qualitative only).

Details of the Science Content

Unwanted energy transfers can be reduced in a number of ways, for example through:

• lubrication – work done against the frictional forces acting on an object causes a rise in the temperature of the object and dissipates useful energy

• the use of thermal insulation – the higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material.

Scientific, Practical and Mathematical Skills

WS 1.4

Explain technological applications of science.

Energy Efficiency

GCSE Science Subject Content

Calculate energy efficiency for any energy transfer, (HT only) and describe ways to increase efficiency.

Details of the Science Content

The energy efficiency for any energy transfer
can be calculated using the equation:

efficiency = useful output energy transfer / total input energy transfer

Scientific, Practical and Mathematical Skills

WS 3.3, MS 3c

Recall and apply this equation.

MS 1a, 1c, 3c

Calculate or use efficiency values as a decimal or as a percentage.

Life Cycle Assessment

GCSE Science Subject Content

Describe the basic principles in carrying out a life cycle assessment of a material or product.
Interpret data from a life cycle assessment of a material or product.

Details of the Science Content

Life cycle assessments (LCAs) are carried out to assess the environmental impact of the materials used and the energy resources needed for products in each of these stages:

• extracting and processing raw materials

• manufacturing and packaging

• use and operation during its lifetime

• disposal at the end of its useful life including transport and distribution at each stage.

The use of water, energy resources and materials, as well as the production of some wastes, can be fairly easily quantified.
Allocating numerical values to pollutant effects is less straightforward and requires value judgements, so LCA is not a purely objective process.
Selective or abbreviated LCAs can be devised to evaluate a product but these can be misused to reach pre-determined conclusions, eg in support of claims for advertising purposes.

Scientific, Practical and Mathematical Skills

WS 1.3, 1.4, 3.3, 3.5

Interpret data from LCAs of materials or products given appropriate information.

MS 1a

Recognise and use expressions in decimal form.

MS 1d

Make estimates of the results of simple calculations.

WS 4.6, MS 2a

Use an appropriate number of significant figures.

WS 3.5, MS 4a

Translate information between graphical and numeric form.

Recycling

GCSE Science Subject Content

Describe a process where a material or product is recycled for a different use, and explain why this is viable.

Details of the Science Content

Reuse and recycling of materials by end users cuts down the use of limited material resources. It can also cut the use of energy resources and the production of waste. Metals can be recycled by melting and recasting or reforming into different products. The amount of separation required for recycling depends on the metal and the properties required of the final product. For example, in steel making some scrap steel is added to the iron from a blast furnace to reduce the amount of iron that needs to be extracted from iron ore.

Scientific, Practical and Mathematical Skills

WS 1.4

Evaluate factors that affect decisions on recycling, given appropriate information.

AQA GCSE COMBINED SCIENCE: SYNERGY

Building Blocks

States of matter

A particle model

Density

Gas Pressure

Heating and Changes of State

Meanings of Purity

Atomic Structure

Scientific Models of the Atom

The Size of Atoms

Sub-Atomic Particles

Isotopes

²³ Na 11

Electrons in Atoms

Electron Microscopy

Cell Structures

Transport Into and Out of Cells

Mitosis and the Cell Cycle

Meiosis

Cell Differentiation

Waves

Transverse and Longitudinal Waves

A Wave Equation

Electromagnetic Waves

Radio Waves (HT only)

Reflection and Refraction of Electromagnetic Waves (HT only)

Transport Over Larger Distances

Respiration

Exchange Surfaces

The Human Circulatory System

Blood Cells

The Human Digestive System

The Human Nervous System

The Human Endocrine System

Plants and Photosynthesis

Meristem Tissue

Plant Structures

Transpiration

Chlorophyll and Other Plant Pigments

Photosynthesis

Factors Affecting the Rate of Photosynthesis

Translocation

Plant Diseases

Lifestyle and Health

Health and Disease

Risk Factors for Non-Communicable Diseases

Treatments for Cardiovascular Disease

Homeostasis

Insulin and diabetes

Human Reproductive Hormones

Contraception

Treatments for Infertility (HT only)

Absorption and Emission of Radiation

Radioactive Decay

Half-Life

Penetration Properties of Radiations

Contamination and Irradiation

Ionising Radiations

Cancer

Spread of Communicable Diseases

Human Communicable Diseases

Defences Against Pathogens

The Human Immune System

Vaccination

Medicines

Testing New Drugs

Genetic Modification

Stem Cells

Interactions Between Different Types of Disease

Development of the Earth’s Atmosphere

The Carbon Cycle

The Greenhouse Effect

Human Impacts on the Climate

Climate Change: Impacts and Mitigation

Pollutants that affect air quality

The Water Cycle

Sources of Potable Water

Ecosystems and Biodiversity

Interdependence and Competition

²³ Na ₁₁