GCSE Combined Science specification checklist

FoundationEvery student

• 1.1Describe plant and animal cells (eukaryotic cells) as having a cell membrane, cytoplasm and genetic material enclosed in a nucleus, and bacterial cells (prokaryotic cells) as much smaller, with cytoplasm and a cell membrane surrounded by a cell wall, and genetic material that is a single DNA loop not enclosed in a nucleus, plus plasmids.
• 1.2Explain how the main sub-cellular structures — nucleus, cell membrane, mitochondria, ribosomes, and in plant cells chloroplasts and a permanent vacuole plus a cellulose cell wall — are related to their functions.
• 1.3Use estimations to explain the relative size and scale of cells, including order-of-magnitude calculations in standard form and the prefixes centi, milli, micro and nano.
• 1.4Explain how the structures of specialised cells — sperm, nerve and muscle cells; root hair, xylem and phloem cells — relate to their functions, and describe cells becoming specialised by differentiation.
• 1.5Carry out the microscopy required practical: use a light microscope to observe, draw and label a selection of plant and animal cells, including a magnification scale, and explain why electron microscopes gave scientists a clearer picture of sub-cellular structures.
• 1.6Use the equation magnification = image size ÷ real size, converting between centimetres, millimetres, micrometres and nanometres.
• 1.7Describe the nucleus as containing chromosomes made of DNA molecules, with each chromosome carrying a large number of genes; in body cells chromosomes are normally found in pairs.
• 1.8Describe the cell cycle: before a cell divides it grows and copies its DNA, during mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides, and finally the cytoplasm and cell membrane divide to form two identical cells — important for the growth and development of multicellular organisms.
• 1.9Describe the function of stem cells in embryonic tissue, in adult bone marrow and in the meristems of plants, and evaluate the benefits and risks of using stem cells in medicine, including therapeutic cloning in which an embryo is produced with the same genes as the patient.

FoundationEvery student

• 2.1Describe diffusion as the spreading out of particles of a substance from an area of higher concentration to an area of lower concentration, down the concentration gradient, and explain how the rate is affected by the concentration gradient, temperature and membrane surface area.
• 2.2Give examples of substances transported into and out of cells by diffusion, including oxygen and carbon dioxide in gas exchange and the waste product urea from cells into blood plasma, and explain why single-celled organisms can rely on diffusion across their surface.
• 2.3Calculate and compare surface area to volume ratios, and explain how multicellular organisms need exchange surfaces and a transport system because their surface-area-to-volume ratio is too small for diffusion alone.
• 2.4Describe osmosis as the diffusion of water through a partially permeable membrane, from a dilute solution (higher water concentration) to a concentrated solution (lower water concentration), and explain how plant cells are supported by osmotic water uptake.
• 2.5Carry out the required practical: investigate the effect of a range of concentrations of salt or sugar solution on the mass of plant tissue, calculating and graphing percentage change in mass, and use the graph to find the concentration of the plant cell sap.
• 2.6Describe active transport as the movement of substances from a more dilute solution to a more concentrated solution against the concentration gradient, requiring energy from respiration, and explain its role in absorbing mineral ions into plant root hairs and sugar from the gut into the blood.
• 2.7Compare diffusion, osmosis and active transport in terms of direction, membrane requirement and energy use.

FoundationEvery student

• 3.1Describe the levels of organisation in living organisms: organelles, cells, tissues, organs and organ systems, with the digestive system as an example of an organ system in which several organs work together.
• 3.2Describe the role of digestive enzymes — amylase, proteases and lipase — in breaking down starch, proteins and lipids into sugars, amino acids and glycerol plus fatty acids, and name the organs that produce each enzyme.
• 3.3Describe where in the digestive system each enzyme acts, and explain the effect of pH and temperature on enzyme activity, including denaturation changing the shape of the active site.
• 3.4Describe the role of bile in neutralising stomach acid and emulsifying fats to increase the surface area for lipase, and name the liver, gall bladder and small intestine in that process.
• 3.5Carry out the required practical: use qualitative reagents to test for carbohydrates, lipids and proteins — Benedict’s test for sugars, iodine test for starch and biuret test for protein.
• 3.6Carry out the required practical: investigate the effect of pH on the rate of reaction of amylase, using continuous sampling with iodine and controlling temperature with a water bath.
• 3.7Calculate the rate of enzyme reactions from timings, and explain how the products of digestion are used to build new carbohydrates, proteins and lipids, with some glucose released in respiration.

FoundationEvery student

• 4.1Describe the heart as a double pump: the right side pumps deoxygenated blood to the lungs to collect oxygen, the left side pumps oxygenated blood around the body, and valves prevent backflow.
• 4.2Describe the structure and function of arteries, veins and capillaries, and explain how their structures suit their jobs, including how capillaries exchange substances with tissues.
• 4.3Describe blood as a tissue containing plasma, red blood cells, white blood cells and platelets, and explain the function of each component, including the transport of oxygen by haemoglobin.
• 4.4Describe coronary heart disease as the build-up of fatty material in the coronary arteries narrowing them and reducing blood flow to the heart muscle, and evaluate stents and statins as treatments.
• 4.5Describe health as the state of physical and mental wellbeing, explain how diseases can interact (for example immune reactions and physical mental health effects), and describe risk factors — including diet, smoking, exercise, alcohol and inherited factors — for non-communicable diseases, interpreting data on their effects.
• 4.6Describe cancer as the result of changes in cells leading to uncontrolled growth and division, distinguish benign tumours (contained in a membrane, not spreading) from malignant tumours (invading tissue and spreading), and link genetic and lifestyle risk factors — including smoking, alcohol, obesity, ionising radiation and viruses — to cancer risk.
• 4.7Calculate rates of blood flow and cardiac output from given data, and interpret graphs of disease incidence against lifestyle factors.

FoundationEvery student

• 5.1Describe the leaf as a plant organ containing tissues: epidermis, palisade mesophyll, spongy mesophyll, xylem, phloem and guard cells around stomata, and relate each tissue to its function.
• 5.2Explain how root hair cells increase the absorbing surface area of roots, and describe the transport of water and mineral ions into the plant.
• 5.3Describe xylem tissue as hollow strengthened tubes that transport water and dissolved mineral ions from the roots to the stems and leaves, and explain the transpiration stream.
• 5.4Describe phloem tissue as living cells with pores in their end walls that transport dissolved sugars from the leaves to the rest of the plant (translocation), for immediate use or storage.
• 5.5Describe how stomata and guard cells open and close to control gas exchange and water loss, and explain the effect of temperature, humidity, air movement and light intensity on the rate of transpiration.
• 5.6Calculate rates of water uptake from practical data, and interpret graphs of transpiration rate against environmental conditions.

FoundationEvery student

• 6.1Describe communicable diseases as those caused by pathogens — viruses, bacteria, fungi and protists — and explain how pathogens are spread by direct contact, air (droplets) and water.
• 6.2Give examples of communicable diseases — measles, HIV, tobacco mosaic virus, salmonella, gonorrhoea, rose black spot and malaria — naming the pathogen type, how each spreads and its main effects or symptoms.
• 6.3Describe the human defence systems — skin, hairs and mucus in the airways, and stomach acid — that prevent pathogens entering the body, and explain the immune response: phagocytes engulfing pathogens and lymphocytes producing antibodies whose shape matches the pathogen’s antigens.
• 6.4Explain how vaccination introduces small quantities of inactive or dead pathogens or their antigens to stimulate antibody production, producing immunity, and evaluate the benefits of herd immunity.
• 6.5Explain that antibiotics cure bacterial infections by killing bacteria (or stopping their growth) but do not work against viruses, that painkillers relieve symptoms without killing pathogens, and describe how antibiotic-resistant strains (such as MRSA) arise and how their spread can be reduced.
• 6.6Describe the discovery of drugs from plants and microorganisms (digitalis, aspirin, penicillin) and the stages of modern drug development: preclinical testing for toxicity and efficacy in cells, tissues and live animals, then clinical trials on healthy volunteers and patients, including double-blind trials with placebos.
• 6.7Interpret data on infection, vaccination coverage and antibiotic resistance, including calculating rates and percentage differences.

FoundationEvery student

• 7.1Describe photosynthesis as an endothermic reaction in which carbon dioxide and water react, using light energy absorbed by chlorophyll, to produce glucose and oxygen, and state the word and balanced symbol equations.
• 7.2Explain the effect of light intensity, carbon dioxide concentration, temperature and (for higher tier) chlorophyll availability on the rate of photosynthesis, and interpret graphs to identify the limiting factor.
• 7.3Carry out the required practical: investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed, and explain the inverse-square relationship between distance and light intensity.
• 7.4Describe the uses of glucose produced by photosynthesis: respiration, conversion into insoluble starch for storage, into cellulose for cell walls, into amino acids (with nitrate ions) for protein, and into lipids for seeds.
• 7.5Describe respiration as an exothermic reaction that transfers energy from glucose, and state the aerobic equation; explain the anaerobic pathway in muscles (lactic acid, oxygen debt) and in yeast and plant root cells (ethanol and carbon dioxide, or carbon dioxide and water in roots).
• 7.6Explain how the body responds during exercise — increased heart rate, breathing rate and breath volume — to supply muscles with more oxygenated blood, and describe metabolism as the sum of all reactions in a cell or body, giving examples.
• 7.7Calculate rates from practical data, use the inverse-square law, and interpret response data from exercise experiments.

FoundationEvery student

• 8.1Explain that homeostasis is the regulation of internal conditions to keep them close to a set optimum, and describe automatic control systems as receptors detecting a stimulus, a coordination centre processing it and effectors producing a response.
• 8.2Describe the structure of the nervous system — the brain and spinal cord forming the central nervous system, connected to the body by neurones — and sequence the reflex arc from stimulus through receptor, sensory neurone, coordination centre and motor neurone to effector.
• 8.3Describe how an impulse crosses a synapse when neurotransmitters diffuse across the gap, and explain why reflexes are fast and automatic because they do not involve the conscious parts of the brain.
• 8.4Carry out the required practical: investigate the effect of a factor (such as caffeine) on human reaction time using the ruler-drop method, converting drop distance to reaction time and using repeats and means.
• 8.5Describe the principles of hormonal coordination: endocrine glands secrete hormones into the blood, the pituitary gland acts as a master gland, and hormones act more slowly but for longer than electrical impulses.
• 8.6Explain how blood glucose concentration is controlled by the pancreas releasing insulin to lower glucose and glucagon to raise it, as an example of negative feedback.
• 8.7Describe Type 1 diabetes as the pancreas producing little or no insulin and Type 2 diabetes as body cells no longer responding to insulin, and evaluate the link between obesity (BMI = mass ÷ height²) and Type 2 diabetes along with their treatments.
• 8.8Describe the roles of testosterone and oestrogen at puberty, the menstrual cycle with its roughly 28-day pattern, and how FSH, LH, oestrogen and progesterone interact (Higher) to control it.
• 8.9Explain how hormones are used in contraception and fertility treatment, including the evaluation of in vitro fertilisation (IVF).

FoundationEvery student

• 9.1Compare sexual reproduction (fusion of gametes from two parents, producing variation) with asexual reproduction (one parent, genetically identical offspring), and describe meiosis as the cell division that makes gametes.
• 9.2Describe DNA as a polymer of two strands coiled into a double helix, a gene as a section of DNA coding for a sequence of amino acids, and the genome as the entire genetic material of an organism, including why studying the human genome matters.
• 9.3Use the language of inheritance — alleles, dominant, recessive, homozygous, heterozygous, genotype, phenotype — and predict the results of crosses with Punnett squares and family trees, including probabilities (Higher).
• 9.4Describe sex determination: body cells contain 23 pairs of chromosomes including the sex chromosomes XX (female) and XY (male), so each pregnancy has an equal chance of each sex.
• 9.5Describe polydactyly as an inherited disorder caused by a dominant allele and cystic fibrosis as one caused by a recessive allele, and describe variation as genetic, environmental or both, arising from mutations and sexual reproduction.
• 9.6Describe mutations as random changes in DNA that occur continuously, most having no effect, and explain Darwin’s theory of evolution by natural selection, including antibiotic-resistant bacteria as a modern example.
• 9.7Describe selective breeding as choosing parents with desired characteristics over generations and genetic engineering as transferring useful genes between organisms, and discuss the benefits and concerns of each.
• 9.8Describe the Linnaean classification system with the binomial naming of species, and interpret evolutionary trees that show how species are related.

FoundationEvery student

• 10.1Describe a population, a community and an ecosystem, and levels of organisation in food chains: producers making glucose by photosynthesis, primary, secondary and tertiary consumers, and the role of decomposers.
• 10.2Carry out the required practical: measure the population size of a common species using quadrats placed randomly, and estimate the whole-habitat population from the mean count per unit area.
• 10.3Describe organisms’ adaptations to their environments as structural, behavioural or functional, including extremophiles living in extreme conditions.
• 10.4Describe the water cycle (evaporation and transpiration, condensation, precipitation) and the carbon cycle (photosynthesis, respiration, combustion, decomposition), including the role of decomposers in returning nutrients.
• 10.5Describe biodiversity as the variety of organisms in an area and explain how human impacts — land use, deforestation, peat destruction, pollution and fertiliser run-off — reduce it.
• 10.6Describe conservation programmes such as protected habitats, breeding programmes and replanting that maintain biodiversity.

FoundationEvery student

• 11.1Describe atoms, elements, compounds and mixtures, and recall the physical separation methods — filtration, crystallisation, simple distillation, fractional distillation and chromatography — choosing one for a given mixture.
• 11.2Describe how the model of the atom developed: indivisible spheres, the plum pudding model, Rutherford’s nuclear model from alpha scattering, Bohr’s shells and Chadwick’s neutron.
• 11.3Describe atoms in terms of protons, neutrons and electrons, use mass numbers and atomic numbers, describe isotopes, and calculate relative atomic mass from isotope abundances (Higher).
• 11.4Write electron configurations up to element 20 and link them to an element’s period and group.
• 11.5Describe how Mendeleev arranged his periodic table, leaving gaps and predicting properties, and how the modern table orders elements by atomic (proton) number.
• 11.6Describe the reactions of Group 1 alkali metals with water and oxygen, and explain the increase in reactivity down the group.
• 11.7Describe the states and colours of Group 7 halogens at room temperature, displacement reactions, and the decrease in reactivity down the group.
• 11.8Describe the unreactivity of Group 0 noble gases in terms of their full outer shells and the trend in their boiling points down the group.

FoundationEvery student

• 12.1Describe the three states of matter in the particle model, the changes of state between them, and conservation of mass during changes of state.
• 12.2Describe ionic bonding: metal atoms losing electrons and non-metal atoms gaining them to form ions with full outer shells, held together by strong electrostatic forces in a giant lattice.
• 12.3Deduce the formulae of ionic compounds from the charges of their ions and draw dot-and-cross diagrams for simple ionic compounds.
• 12.4Describe covalent bonding as the sharing of electron pairs in simple molecules and giant structures, and draw dot-and-cross diagrams for molecules such as H₂, HCl, H₂O, CH₄, O₂ and NH₃.
• 12.5Explain the properties of ionic compounds (high melting points, conduction when molten or dissolved) and of simple molecular substances (low melting points, no conduction) in terms of their bonding and structure.
• 12.6Describe polymers as long covalently bonded chains and metals as giant lattices of positive ions in a sea of delocalised electrons, and explain their properties, including why alloys are harder than pure metals.
• 12.7Describe the allotropes of carbon — diamond, graphite, graphene and fullerenes — linking each structure to its properties and uses.

FoundationEvery student

• 13.1Explain conservation of mass in chemical reactions — atoms are rearranged, never created or destroyed — and account for apparent mass changes when gases enter or escape.
• 13.2Balance symbol equations by adjusting the large balancing numbers, and write balanced equations with state symbols (s), (l), (g) and (aq).
• 13.3Calculate the relative formula mass (Mr) of a compound from relative atomic masses.
• 13.4Calculate the concentration of a solution in g/dm³ from the mass of solute and the volume of solution, converting cm³ to dm³.
• 13.7Estimate the uncertainty in a mean from repeated measurements as half the range.

HigherHigher tier only

• 13.5(Higher) Use the Avogadro constant, convert between mass and moles with moles = mass ÷ Mr, and calculate reacting masses from balanced equations.
• 13.6(Higher) Identify the limiting reactant from amounts in moles and calculate the maximum mass of product.

FoundationEvery student

• 14.1Describe the reactivity series as metals ranked by how readily they form positive ions, with carbon and hydrogen as reference points, and recall the order for common metals.
• 14.2Describe how metals react with dilute acids and with water, and use observations to place metals in order of reactivity.
• 14.3Describe displacement reactions: a more reactive metal displaces a less reactive metal from its salt solution, and explain the observation-based evidence.
• 14.4Define oxidation as the gain of oxygen and reduction as the loss of oxygen, and identify both in reactions such as metal extraction; (Higher) explain oxidation and reduction as loss and gain of electrons (OIL RIG).
• 14.5Explain how metals less reactive than carbon are extracted from their ores by reduction with carbon, and why metals above carbon need electrolysis.
• 14.6Describe why unreactive metals such as gold are found native in the Earth.

HigherHigher tier only

• 14.7(Higher) Describe alternative extraction methods for low-grade ores — phytomining and bioleaching — and evaluate their advantages and disadvantages.

FoundationEvery student

• 15.1Use the pH scale from 0 to 14: acids below 7, neutral solutions exactly 7, alkalis above 7; describe acids as sources of hydrogen ions, H⁺(aq), aqueous alkalis as sources of hydroxide ions, OH⁻(aq), and neutralisation as H⁺(aq) + OH⁻(aq) → H₂O(l) with a salt as the other product; measure pH with universal indicator or a pH probe.
• 15.2Describe and write equations for the reactions of acids with metals (salt + hydrogen), metal oxides and hydroxides (salt + water) and metal carbonates (salt + water + carbon dioxide), and predict the salt formed from the acid family (chloride, sulfate, nitrate) and the metal ion of the other reagent.
• 15.3Describe the required practical of preparing a pure, dry sample of a soluble salt from an insoluble base: warming the dilute acid, adding the base in excess, filtering, evaporating to crystallisation and cooling, including the variables, hazards and why each step matters.
• 15.5Describe electrolysis as decomposition by electricity, possible only when an ionic compound is molten or dissolved so its ions can move; identify the negative cathode (attracting cations) and positive anode (attracting anions), and predict the products of electrolysis of a molten binary ionic compound.
• 15.6Explain the extraction of aluminium: molten aluminium oxide with cryolite added to lower the operating temperature, aluminium at the cathode, oxygen at the anode, carbon anodes burning away, and why the process is so energy-hungry.
• 15.7Predict the products of aqueous electrolysis with inert electrodes — hydrogen at the cathode unless the metal is less reactive than hydrogen, halogen at the anode if a halide is present, otherwise oxygen — and describe the required practical of electrolysing aqueous solutions (concentrated sodium chloride, copper(II) sulfate, dilute sulfuric acid) with gas tests.
• 15.9Describe uses of neutralisation, including treating acidic soil with calcium hydroxide (liming) and neutralising acid indigestion with antacid bases.

HigherHigher tier only

• 15.4(Higher) Distinguish strong acids (fully ionised in aqueous solution — hydrochloric, sulfuric, nitric) from weak acids (partially ionised — ethanoic, citric), and explain that as pH decreases by one unit the hydrogen ion concentration increases by a factor of ten.
• 15.8(Higher) Write half equations for the reactions at each electrode, balanced for atoms and charge, and explain reduction as electron gain at the cathode and oxidation as electron loss at the anode; explain observations such as the 2 : 1 hydrogen-to-oxygen volume ratio and the fading blue of copper sulfate solution.

FoundationEvery student

• 16.1Distinguish exothermic reactions, which transfer energy to the surroundings and raise the temperature (combustion, many oxidations, neutralisation), from endothermic reactions, which take in energy from the surroundings and lower the temperature (thermal decomposition, citric acid with sodium hydrogencarbonate).
• 16.2Describe everyday applications of energy changes, including hand warmers (iron rusting or salt crystallisation), self-heating cans (a metal oxide reacting with water) and self-chilling cans (an endothermic dissolving reaction).
• 16.3Draw and interpret reaction profiles: in an exothermic reaction the products sit at lower energy than the reactants with a negative ΔH; in an endothermic reaction the products sit higher with a positive ΔH.
• 16.6Describe the required practical of investigating the temperature changes in reacting solutions: adding measured portions of alkali to acid in a polystyrene cup, recording the maximum temperature after each addition, and identifying the reacting ratio from the maximum temperature change; include variables, hazards and evaluation.

HigherHigher tier only

• 16.4(Higher) Define the activation energy as the minimum energy particles need to react, identify it on a reaction profile from the reactants up to the peak, and explain that a catalyst lowers the activation energy without changing ΔH.
• 16.5(Higher) Explain that bond breaking is endothermic and bond making is exothermic, and calculate the overall energy change using ΔH = energy to break bonds − energy released making bonds, given bond energies in kJ/mol.

FoundationEvery student

• 17.1Calculate the mean rate of a reaction from the quantity of product formed or reactant used divided by the time taken, with units such as cm³/s, g/s or mol/s.
• 17.2Describe the factors that change the rate — concentration or pressure, temperature, surface area of solids and catalysts — and explain each using collision theory: reactions need collisions with at least the activation energy, and factors raise collision frequency or energy.
• 17.3Describe catalysts as substances that increase the rate by providing a lower-activation-energy route while remaining chemically unchanged and unchanged in mass at the end.
• 17.4Interpret rate graphs: the steepest section is the fastest rate, the curve flattens when a reactant is used up, and the rate at a chosen moment is found from the gradient of a tangent to the curve.
• 17.5Describe the required practical of investigating how concentration changes the rate — by the disappearing-cross (precipitate) method or by collecting gas — including the variables that must be controlled, the method, and the use of 1/time comparisons.
• 17.6Describe reversible reactions (such as hydrated and anhydrous copper(II) sulfate) and dynamic equilibrium: in a closed system the forward and reverse reactions run at equal rates, so the amounts of reactants and products stay constant.

HigherHigher tier only

• 17.7(Higher) Predict, using the principle that an equilibrium shifts to oppose a change, the effect of changing concentration or pressure on the position of equilibrium (for example, increasing pressure favours the side with fewer gas molecules).

FoundationEvery student

• 18.1Describe crude oil as a finite resource formed over millions of years from the remains of ancient marine organisms, and as a mixture of hydrocarbons — compounds containing hydrogen and carbon only.
• 18.2Describe fractional distillation: crude oil is heated and its fractions condense at different temperatures in a fractionating column, with short-chain fractions condensing near the cool top and long-chain fractions near the hot bottom.
• 18.3Recall that alkanes are saturated hydrocarbons with the general formula CnH2n+2, name the first four (methane, ethane, propane, butane), and describe the trends as chain length increases — higher boiling point, greater viscosity, lower flammability.
• 18.4Describe complete combustion of hydrocarbons (carbon dioxide and water) and incomplete combustion in a limited oxygen supply, which additionally produces carbon monoxide and soot (carbon particles), and explain why carbon monoxide is toxic.
• 18.5Describe the pollutants released by burning fossil fuels — carbon dioxide, carbon monoxide, soot, sulfur dioxide and oxides of nitrogen — and their effects, including global warming, acid rain and harm to health.
• 18.6Describe cracking as the splitting of long, less useful alkane molecules into shorter alkane and alkene molecules using heat and a catalyst, explain why it is needed commercially, and write balanced cracking equations.
• 18.7Describe alkenes as unsaturated hydrocarbons with the general formula CnH2n containing a carbon-to-carbon double bond, and describe the bromine-water test: alkenes decolourise orange bromine water, alkanes do not.

FoundationEvery student

• 19.1Describe a pure substance as a single element or compound (not a mixture), and explain that pure substances melt and boil at specific temperatures, while impurities widen the melting range and lower the melting point.
• 19.2Describe formulations as mixtures designed for a specific purpose, in which each component is present in a measured amount, with examples such as fuels, alloys, fertilisers, medicines and cleaning products.
• 19.3Describe paper chromatography: the mobile phase (the solvent) moves through the stationary phase (the paper), and dissolved substances separate because they have different attractions for the two phases.
• 19.4Calculate Rf values (distance moved by the substance divided by distance moved by the solvent), use reference values to identify substances, and interpret chromatograms — the number of spots — to judge how many substances and whether a sample is pure.
• 19.5Carry out the paper chromatography required practical: run known and unknown food colourings on the same paper, describe the method, variables, hazards and typical results, and use Rf values to identify an unknown dye.
• 19.6Describe the tests for gases: hydrogen — a lighted splint gives a squeaky pop; oxygen — a glowing splint relights; carbon dioxide — limewater turns cloudy; chlorine — damp litmus paper is bleached white.

FoundationEvery student

• 20.1Describe the evolution of the atmosphere in phases: volcanoes releasing gases (mainly carbon dioxide with water vapour and nitrogen), the oceans forming as water vapour condensed and dissolving much of the carbon dioxide, and green plants and algae raising the oxygen level through photosynthesis.
• 20.2Describe today's atmosphere as approximately 78% nitrogen, 21% oxygen, about 1% argon and around 0.04% carbon dioxide.
• 20.3Describe the greenhouse effect — water vapour, carbon dioxide and methane absorbing outgoing long-wave radiation and re-radiating it back — and the enhanced greenhouse effect from rising human emissions, plus the peer-reviewed, multi-source evidence for human-caused climate change.
• 20.4Describe the carbon footprint as the total greenhouse gases emitted over the full life cycle of a product, service or event; describe ways to reduce it and explain why reductions are difficult (international cooperation needed, economic costs).
• 20.5Describe the common atmospheric pollutants from burning fuels — carbon monoxide, soot (particulates), sulfur dioxide and oxides of nitrogen — how each forms, and their effects (toxicity, health problems, global dimming, acid rain).
• 20.6State that Earth's resources are finite (used faster than they form) or renewable, and describe what sustainable development requires.
• 20.7Describe potable water as water safe to drink but not chemically pure, and its production: choosing a fresh source, sedimentation and filtration to remove solids, sterilisation with chlorine, ozone or ultraviolet light; and desalination of seawater by distillation or reverse osmosis, with their energy costs.
• 20.8Describe how urban waste water is treated: screening, sedimentation into sludge and effluent, anaerobic digestion of sludge producing biogas, and aerobic biological treatment of the effluent before safe release.
• 20.10Describe a life cycle assessment (extraction of raw materials, manufacturing, packaging and transport, use, disposal), explain why LCAs can be subjective and selective, and describe reduce, reuse and recycle as ways to cut resource use, including the energy saved compared with extracting and processing raw materials.

HigherHigher tier only

• 20.9Describe (Higher) alternative ways of extracting copper from low-grade ores: phytomining — plants absorb copper ions, are harvested and burned, and the metal is obtained from the ash — and bioleaching — bacteria produce a solution (leachate) containing copper compounds — followed by displacement with scrap iron or electrolysis.

FoundationEvery student

• 21.1Identify the energy stores — kinetic, gravitational potential, elastic potential, thermal, chemical, magnetic, electrostatic and nuclear — and describe systems changing between them (an object accelerated by a force, a ball thrown upwards, a vehicle braking, a kettle boiling water).
• 21.2State the principle of conservation of energy: energy cannot be created or destroyed, only transferred between stores; in a closed system the total energy stays constant.
• 21.3Calculate kinetic energy (E = ½mv²), gravitational potential energy (E = mgh) and elastic potential energy (E = ½ke²), choosing the right equation and units.
• 21.4Define power as the energy transferred per second, calculate P = E ÷ t, and use appliance power ratings to find the energy transferred over a time.
• 21.5Describe dissipation: unwanted energy transfers end up as less useful stores (usually thermal energy of the surroundings), and explain how lubrication reduces friction and thermal insulation (thickness and low thermal conductivity) reduces heating losses.
• 21.6Calculate efficiency as useful energy output ÷ total energy input (or useful power ÷ total power), as a ratio or percentage, and explain why devices can never be fully efficient and how design improves efficiency.
• 21.7Define specific heat capacity and calculate the change in thermal energy using ΔE = mcΔθ.
• 21.8Carry out the required practical: measure the specific heat capacity of a metal (or water) using a heater and joulemeter or an ammeter–voltmeter circuit, controlling the method, identifying variables, hazards and sources of error.

FoundationEvery student

• 22.1List the main energy resources: fossil fuels (coal, oil, gas), nuclear fuel, biofuel, wind, hydroelectricity, geothermal, the tides, the Sun and water waves.
• 22.2Describe how energy resources are used — generating electricity, heating, cooking and transport — and which resources dominate each use.
• 22.3Distinguish renewable resources, which are replenished as they are used, from non-renewable resources, which are consumed faster than they form.
• 22.4Describe the environmental issues of each resource: landscape and wildlife damage, noise, carbon dioxide and other emissions, and the decommissioning of power stations.
• 22.5Explain why some resources are more reliable than others: some generate whatever the weather or time of day, while others depend on sunshine, wind or rainfall.
• 22.6Describe trends in the use of energy resources, including the historic dependence on (and decline of) fossil fuels and the growth of renewables in the UK energy mix.
• 22.7Calculate domestic energy use and cost in kilowatt-hours: energy transferred (kWh) = power (kW) × time (h), and cost = number of kWh × price per kWh, knowing 1 kWh = 3.6 MJ.
• 22.8Evaluate the use of different energy resources for a given purpose, weighing reliability, environmental effects, cost and scale — and explain why variable renewables still need reliable backup or storage.

FoundationEvery student

• 23.1Draw and interpret standard circuit symbols: cell, battery, switch, lamp, resistor, variable resistor, ammeter, voltmeter, diode, thermistor, LDR, LED and fuse.
• 23.2Describe current as the rate of flow of charge, measured in amperes by an ammeter in series, and calculate charge flow using Q = It.
• 23.3Describe potential difference as energy transferred per unit charge, measured in volts by a voltmeter in parallel, and use V = IR to link potential difference, current and resistance.
• 23.4State the series-circuit rules: current is the same at every point, the supply p.d. is shared between components, and total resistance is the sum of the separate resistances.
• 23.5State the parallel-circuit rules: each branch receives the full supply p.d., the total current is the sum of the branch currents, and adding resistors in parallel reduces the total resistance.
• 23.6Interpret the I–V characteristics of a fixed resistor (straight line through the origin at constant temperature), a filament lamp (curve that flattens as heating raises its resistance) and a diode (conducts in one direction only, above about 0.7 V forwards).
• 23.7Describe applications of thermistors (their resistance falls as temperature rises) and LDRs (resistance falls as light level rises) in sensing circuits such as thermostats and automatic night lights.
• 23.8Explain why the resistance of a wire increases with length and decreases with cross-sectional area, using the model of electrons drifting through a lattice of vibrating ions.
• 23.9Carry out the required practicals: measure how a wire's resistance depends on its length (and investigate resistor combinations in series and parallel), and use a variable-resistor circuit to obtain the I–V characteristics of a fixed resistor, a filament lamp and a diode.

HigherHigher tier only

• 23.10Calculate currents, p.d.s and total resistance in mixed series–parallel circuits, and explain qualitatively why parallel connections lower resistance (more paths for charge).

FoundationEvery student

• 24.1Describe direct potential difference (d.c.) as a p.d. that keeps the same polarity, and alternating potential difference (a.c.) as a p.d. that repeatedly reverses polarity; recall that UK mains is a.c. at about 230 V with a frequency of 50 Hz.
• 24.2Describe the functions of the live, neutral and earth wires, their colour coding (brown, blue, green-and-yellow stripes), and explain why the live wire is dangerous even when a switch in it is open.
• 24.3Explain how fuses, circuit breakers and earthing protect users and cables: a fault current through the earth connection blows the fuse and disconnects the live supply; the switch and fuse are always placed in the live wire.
• 24.4Explain why appliances with plastic (insulating) cases need no earth wire — double insulation — and select an appropriate fuse rating slightly above an appliance's normal operating current.
• 24.5Calculate the power of mains appliances using P = V I, and the energy transferred using E = P t, in both joules and kilowatt-hours, including the cost of domestic electricity from meter readings.
• 24.6Describe the National Grid as the network of cables and transformers that carries electrical power from power stations to consumers, using step-up transformers before transmission and step-down transformers before local supply.
• 24.8Describe how a transformer works only with a.c. — the changing current in the primary coil produces a changing magnetic field that induces a p.d. across the secondary coil — and state that step-up transformers raise voltage (lowering current) while step-down transformers lower it for safe domestic use.

HigherHigher tier only

• 24.7Explain, using P = I² R, why the Grid transmits power at very high voltage and correspondingly low current: heating losses in the cables scale with the square of the current, so a small current keeps the wasted power small.

FoundationEvery student

• 25.1Describe the particle model: solids have particles vibrating about fixed positions in a regular arrangement, liquid particles are close together but free to move past one another, and gas particles are far apart and move rapidly in random directions.
• 25.2Describe changes of state (melting, freezing, evaporation, boiling, condensation, sublimation) as physical changes that conserve mass, and explain internal energy as the total kinetic and potential energy stored by the particles.
• 25.3Calculate density using ρ = m/V, in kg/m³ and g/cm³, and convert between them (1 g/cm³ = 1000 kg/m³).
• 25.4Carry out the density required practical: measure the density of a regular solid from its dimensions, of an irregular solid by displacement of water (displacement can or measuring cylinder) and of a liquid using a balance and measuring cylinder.
• 25.5Explain heating curves and cooling curves: temperature rises while one state is heated, and holds constant during a change of state because the energy supplied goes into changing particle arrangements rather than raising temperature.
• 25.7Explain gas pressure as the result of particles colliding with the walls of a container, and explain why heating a gas in a sealed, rigid container raises the pressure (faster particles collide harder and more often).
• 25.9Explain how doing work on a gas (compressing it quickly, as in a bike pump) raises its internal energy and its temperature.

HigherHigher tier only

• 25.6Calculate the energy for a change of state using E = m L, for both fusion (melting) and vaporisation (boiling); specific latent heat is the energy needed to change the state of 1 kg with no change in temperature.
• 25.8Calculate changes in gas pressure and volume at constant temperature using p₁ V₁ = p₂ V₂, and explain qualitatively why reducing the volume raises the pressure.

FoundationEvery student

• 26.1Describe the structure of the atom: a nucleus of protons and neutrons surrounded by electrons at set distances (energy levels), with an atom radius of about 1 × 10⁻¹⁰ m and a nucleus about 10 000 times smaller.
• 26.2Recall the charges and masses of protons, neutrons and electrons; use atomic number Z (number of protons) and mass number A (protons + neutrons); define isotopes as atoms of the same element with different numbers of neutrons, and describe positive and negative ion formation.
• 26.3Describe how the atomic model developed: the plum pudding model, the alpha-scattering experiment (most alpha particles passed through the foil; a few bounced back), the nuclear model, Bohr's shells and Chadwick's discovery of the neutron.
• 26.4Describe radioactive decay: unstable nuclei emit radiation to become stable; decay is random and spontaneous; activity is the rate of decay, measured in becquerels (Bq), and is unaffected by temperature, pressure or chemical bonding.
• 26.5Compare alpha particles (helium nuclei, highly ionising, stopped by paper), beta-minus particles (fast electrons from the nucleus, moderately ionising, stopped by a few millimetres of aluminium) and gamma rays (electromagnetic waves, weakly ionising, reduced by thick lead or concrete).
• 26.6Use and balance nuclear equations: mass number A and atomic number Z are conserved; alpha emission lowers A by 4 and Z by 2; beta-minus emission raises Z by 1 (a neutron changes into a proton and an electron) and leaves A unchanged.
• 26.7Define half-life as the time for half the unstable nuclei in a sample to decay, or for the activity (corrected count rate) to halve; read and sketch decay curves and calculate activity after whole numbers of half-lives.
• 26.8Describe sources of background radiation: radon gas from rocks and soil (the largest natural contributor in many UK homes), cosmic rays, radioactive materials in food and buildings, plus man-made sources such as medical uses and the nuclear industry.
• 26.9Distinguish radioactive contamination (radioactive material where it should not be) from irradiation (exposure to radiation from a source elsewhere), and describe how each creates hazard.
• 26.10Describe uses and risks: medical tracers (gamma emitters with short half-lives), radiotherapy, sterilising sealed instruments and radiocarbon dating; alpha sources are most dangerous inside the body, gamma outside; safe handling uses shielding, distance and short exposure times.

FoundationEvery student

• 27.1Distinguish scalars (speed, distance, mass, time, energy) from vectors (velocity, displacement, force, weight, acceleration); recall that weight is a force measured in newtons, calculated as W = m g, acting through the centre of mass.
• 27.2Find the resultant of forces along a straight line and draw free-body diagrams; explain that zero resultant force means rest or constant velocity, and that a non-zero resultant force changes the velocity.
• 27.3Interpret distance–time and velocity–time graphs: speed is the gradient of a d–t graph, acceleration is the gradient of a v–t graph, and distance travelled is the area under a v–t graph.
• 27.4Calculate acceleration with a = (v − u) ÷ t, including decelerations as negative accelerations.
• 27.5Apply Newton's first law (no resultant force → no change in velocity), Newton's second law as F = m a, and Newton's third law (pairs of equal, opposite forces acting on different objects).
• 27.6Carry out the acceleration required practical: vary the applied force on a trolley of constant mass (falling weights over a pulley), using light gates or ticker timers, with a tilted runway compensating friction; the graph of acceleration against force is a straight line through the origin.
• 27.7Carry out the force–extension required practical: adding loads to a spring gives a straight-line graph of force against extension in the linear region, F = k e with spring constant k in N/m; beyond the limit of proportionality the graph curves and the spring may deform.
• 27.8Describe stopping distance as thinking distance plus braking distance: thinking distance grows with speed and reaction time (tiredness, alcohol, distractions); braking distance grows with speed, vehicle condition (brakes, tyres), road condition and mass.
• 27.9Explain why braking distance grows with the square of the speed: the work done by the brakes equals the kinetic energy (½ m v²), so doubling the speed quadruples the braking distance; very large decelerations overheat brakes and endanger passengers.
• 27.10Explain terminal velocity qualitatively: as speed grows, drag grows until it balances the weight, the resultant force falls to zero and the object moves at a steady speed (e.g. a skydiver before the parachute opens).

FoundationEvery student

• 28.1Describe work done as energy transferred by a force: W = F s, where s is the distance moved along the line of action of the force, measured in joules (1 J = 1 N m).
• 28.2Explain that work done against friction transfers energy to the thermal store of the surfaces (and surroundings), which is why machines and moving objects warm up.
• 28.3Calculate power as energy transferred per second, P = E ÷ t, in watts, and use it to compare machines, including lifting (P = m g h ÷ t in context).
• 28.4Describe the filling and release of elastic potential energy in contexts such as bows, catapults and springs, linking the work done stretching to the energy later transferred (the ½ k e² equation itself is met in chapter 21).
• 28.8Explain how road and sport safety features — crumple zones, air bags, seat belts, cycle helmets and gym mats — protect people by extending the time over which momentum changes, so reducing the peak force on the body.

HigherHigher tier only

• 28.5Calculate momentum as p = m v, in kilogram metres per second, remembering that momentum is a vector with direction shown by signs.
• 28.6Use conservation of momentum in a closed system: the total momentum before a collision or explosion equals the total momentum after — including objects that couple together and recoil problems.
• 28.7Relate force to the rate of change of momentum, F t = Δ(m v): for a fixed momentum change, a longer contact time means a smaller force.

FoundationEvery student

• 29.1Describe waves as ripples that transfer energy without any net transfer of matter, distinguishing transverse waves (oscillations perpendicular to the direction of travel) from longitudinal waves (oscillations parallel to it), with examples of each.
• 29.2Define amplitude, wavelength, frequency and period; recall that period = 1 ÷ frequency (given when needed) and that frequency is measured in hertz; and recall and apply the wave equation v = f λ.
• 29.3Describe how to measure the frequency, wavelength and speed of waves in a ripple tank and waves on a stretched string, including counting waves passing a point, freezing the pattern with a stroboscope, and timing oscillations of a suspended string.
• 29.4Describe reflection at a boundary (angle of incidence = angle of reflection) and refraction as a change in direction when a wave crosses into a medium where its speed is different, remembering that frequency stays constant while speed and wavelength change.
• 29.5Describe sound as a longitudinal wave made by vibrating objects that needs a medium to travel, recall the approximate human hearing range of 20 Hz to 20 kHz, and note that sound reflects (echoes) and can be refracted.
• 29.6Describe seismic waves produced by earthquakes: P-waves (longitudinal, faster) and S-waves (transverse, slower), and explain how their paths provide evidence for the structure of the Earth, including the S-wave shadow as evidence for a liquid outer core.
• 29.7Describe electromagnetic waves as transverse waves that transfer energy from a source to an absorber, travel at the same speed (3 × 10⁸ m/s) through a vacuum, and form one continuous spectrum in order of wavelength and frequency: radio, microwave, infrared, visible light, ultraviolet, X-rays and gamma rays.
• 29.8Recall one practical use and one hazard for each part of the electromagnetic spectrum: radio (broadcasting), microwaves (satellite communication, cooking), infrared (heaters, thermal imaging, optical fibres, short-range controls), visible light (vision, illumination, photography), ultraviolet (fluorescent and energy-saving lamps, sterilising water), X-rays (medical imaging of bones) and gamma rays (cancer treatment, sterilising equipment).
• 29.9Describe the hazards of electromagnetic waves: heating of body tissue by microwaves, skin burns from infrared, skin damage and eye damage from ultraviolet, and mutation or cancer risk from the ionising X-rays and gamma rays, with the risk increasing as frequency increases.
• 29.10Describe that all bodies emit infrared radiation and that the hotter a body is, the more infrared it radiates in a given time; and recall the infrared practical comparing emission and absorption by different surfaces (matt black best, shiny silver worst).

FoundationEvery student

• 30.1Describe permanent and induced magnets, the attraction of magnetic materials (iron, steel, cobalt, nickel), the forces between poles (unlike poles attract, like poles repel), and magnetic fields as the region around a magnet where a magnetic material experiences a force, with field lines running from the north pole to the south pole outside the magnet.
• 30.2Describe how to plot the magnetic field around a bar magnet using a plotting compass, and explain that the compass needle points along the field line because it is itself a small magnet.
• 30.3Describe the magnetic field of a solenoid (a current-carrying coil) as matching a bar magnet’s field, and explain how an electromagnet is made and strengthened — more turns, a larger current, an iron core — with applications such as scrapyard cranes, relays and electric door locks.
• 30.4Describe the motor effect: a wire carrying a current in a magnetic field experiences a force; the force is largest when the wire is perpendicular to the field and zero when parallel, grows with the magnetic flux density, the current and the length of wire in the field, and reverses if either the current or the field direction reverses.

HigherHigher tier only

• 30.5Use Fleming’s left-hand rule to predict the direction of the motor-effect force, and calculate the force with F = B I L, with flux density in teslas, current in amperes and length in metres.
• 30.6Explain how a DC electric motor works: opposite forces on the two sides of a current-carrying coil in a field turn the coil, and the split-ring commutator reverses the current every half turn so the rotation continues in one direction; the motor turns faster with a larger current or stronger field, and reverses if the current (or field) is reversed.