Revision / Bio
AQA · Higher Tier · Triple Science · Paper 1

Paper One,
Biology
essentials.

Required practicals, six-marker model answers, key definitions, and equations — distilled for grade 9. Toggle between subjects in the header.

Required Practicals

Biology Paper 1 · 5 practicals
RP 01

Microscopy

Topic 1 · Cell Biology

Method

  1. Place onion cell on slide, add a drop of iodine stain.
  2. Lower coverslip with a mounted needle at 45° to avoid air bubbles.
  3. Start on the lowest objective lens, focus with coarse then fine knob.
  4. Move to higher magnification once focused.
  5. Draw with sharp pencil, clear continuous lines, no shading, label with ruler.

Calculations

Magnification = image size ÷ real size. Always convert units (1 mm = 1000 μm).

Why iodine?

Stains starch granules so structures show up clearly under the microscope.

RP 02

Osmosis in Potatoes

Topic 1 · Cell Biology

Method

  1. Cut potato cylinders to equal size with a cork borer; dry on paper towel; measure initial mass.
  2. Place into different sugar solution concentrations (0.0, 0.2, 0.4, 0.6, 0.8, 1.0 mol/dm³).
  3. Leave for set time (e.g. 30 min) at the same temperature.
  4. Dry and reweigh; calculate % change in mass.

Why % change?

Allows fair comparison even if initial masses differ slightly.

Results

Mass increases in dilute (water in by osmosis), decreases in concentrated. Point where line crosses x-axis = concentration of potato cytoplasm.

Pat potatoes dry before weighing — surface water inflates final mass and ruins reliability.
RP 03

Food Tests

Topic 2 · Organisation

Tests & positive results

NutrientReagentPositive
StarchIodine solutionBlue-black
Reducing sugarBenedict's + heatBrick-red
ProteinBiuret reagentPurple/lilac
LipidEthanol + waterCloudy white
Grind food with water first to release nutrients, then filter.
RP 04

Enzymes (Amylase pH)

Topic 2 · Organisation

Method

  1. Place a drop of iodine in each well of a spotting tile.
  2. Mix starch, amylase and pH buffer in a test tube.
  3. Every 30 seconds, remove a drop and add to iodine.
  4. Record time when iodine stops turning blue-black (starch fully digested).
  5. Repeat at different pH (3, 5, 7, 9, 11).

Result

Amylase has optimum pH around 7. Outside this, the active site denatures, no enzyme-substrate complex forms, rate falls.

Don't say enzymes "die" — they denature. Active site changes shape, substrate no longer fits.
RP 05

Photosynthesis (Pondweed)

Topic 4 · Bioenergetics

Method

  1. Submerge pondweed (Cabomba/Elodea) in dilute sodium hydrogencarbonate (CO₂ source) in a boiling tube.
  2. Place lamp at fixed distance; allow to equilibrate.
  3. Count bubbles released per minute (or measure O₂ volume with a gas syringe — more accurate).
  4. Repeat at different distances (10, 20, 30, 40 cm).

Inverse square law

Light intensity ∝ 1/distance². Doubling distance = ¼ the intensity. Plot rate vs 1/d² for a straight line.

Controls

Use a water bath/beaker of water between lamp and tube to absorb heat — keeps temperature constant.

Six-Mark Questions

Full-mark model answers · Biology Paper 1
"Explain how substances are exchanged in the alveoli."
6 marks

Model Answer

  1. Alveoli have a large surface area due to millions of tiny air sacs, increasing space for diffusion.
  2. Walls are one cell thick (single layer of squamous epithelium), giving a short diffusion distance.
  3. Surrounded by a dense capillary network, which carries oxygen away quickly and brings CO₂ in, maintaining a steep concentration gradient.
  4. Moist lining allows gases to dissolve before diffusing.
  5. Oxygen diffuses from alveolus (high concentration) → blood (low concentration).
  6. Carbon dioxide diffuses the opposite way, from blood → alveolus, and is exhaled.
Always link a feature to how it speeds up diffusion — examiners credit the explanation, not just listing features.
"Explain how the heart and circulatory system are adapted for their function."
6 marks

Model Answer

  1. The heart is a double pump: right side pumps deoxygenated blood to the lungs, left side pumps oxygenated blood to the body.
  2. The left ventricle has a thicker muscular wall than the right, generating higher pressure to pump blood around the whole body.
  3. Valves (tricuspid, bicuspid, semilunar) prevent backflow, ensuring one-way circulation.
  4. Arteries have thick muscular elastic walls and narrow lumens to withstand high pressure.
  5. Capillaries are one cell thick with permeable walls, allowing exchange of oxygen, glucose and waste.
  6. Veins have wider lumens, thinner walls and valves to return low-pressure blood to the heart.
"Describe how non-communicable diseases like cardiovascular disease can be treated."
6 marks

Model Answer — give pros AND cons

  1. Statins: drugs that lower LDL cholesterol, slowing fatty deposits in arteries. Negatives: long-term medication, side effects (headache, muscle pain), don't reverse damage.
  2. Stents: mesh tubes inserted into narrowed coronary arteries to keep them open. Negatives: risk of infection/blood clots, surgery required.
  3. Heart transplant or artificial heart: for end-stage failure. Negatives: donor shortage, risk of rejection (need immunosuppressants).
  4. Lifestyle changes: reduce saturated fat, more exercise, stop smoking. Cheap and preventative but rely on patient.
  5. Treatment choice depends on severity, age, other conditions, and patient preference.
  6. Best approach: prevention through public health — exercise programmes, smoking bans, sugar tax.
"Evaluate" or "discuss" questions need both sides — strengths + limitations + a final judgement.
"Explain how the body controls blood glucose concentration." (HIGHER)
6 marks

Model Answer

  1. Controlled by negative feedback involving the pancreas.
  2. When blood glucose is too high (e.g. after a meal): pancreas releases insulin.
  3. Insulin causes liver and muscle cells to absorb glucose and convert it to glycogen for storage.
  4. When blood glucose is too low (e.g. after exercise): pancreas releases glucagon.
  5. Glucagon causes the liver to break glycogen back down into glucose, releasing it into the blood.
  6. This is a homeostatic mechanism — keeps glucose within narrow limits despite intake and demand.
"Compare cancerous tumours: benign vs malignant."
6 marks

Model Answer

  1. Both result from uncontrolled cell division producing a mass of cells.
  2. Benign tumours stay in one place, usually inside a membrane, and don't invade other tissues.
  3. Benign tumours are not usually life-threatening but can cause issues if pressing on organs (e.g. brain).
  4. Malignant tumours grow and invade neighbouring tissues.
  5. Malignant cells can break off and spread via the blood to form secondary tumours — this is metastasis.
  6. Malignant tumours are cancers and are life-threatening.

Key Definitions

Examiner-approved wording
Diffusion
Net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient.
Osmosis
Movement of water from a dilute solution to a more concentrated solution across a partially permeable membrane.
Active Transport
Movement of substances against a concentration gradient, requiring energy from respiration.
Mitosis
Cell division producing two genetically identical diploid daughter cells. Used for growth, repair and asexual reproduction.
Stem Cell
An undifferentiated cell capable of dividing to produce more stem cells or specialised cells.
Enzyme
A biological catalyst (protein) that speeds up reactions without being used up. Works by lock-and-key model.
Denatured
The active site of an enzyme changes shape so the substrate no longer fits — no enzyme-substrate complex forms.
Aerobic Respiration
Glucose + Oxygen → Carbon dioxide + Water (+ energy). Occurs in mitochondria.
Anaerobic Respiration (animal)
Glucose → Lactic acid (+ small amount of energy). No oxygen needed.
Photosynthesis
Endothermic reaction: Carbon dioxide + Water → Glucose + Oxygen, using light energy absorbed by chlorophyll.
Limiting Factor
The factor in shortest supply that prevents the rate of a reaction increasing further (light, CO₂, temp, chlorophyll).
Communicable Disease
A disease caused by a pathogen that can be passed from one organism to another.
Pathogen
A microorganism that causes infectious disease (bacteria, viruses, fungi, protists).
Antibody
A protein produced by lymphocytes that binds to a specific antigen on a pathogen, marking it for destruction.
Vaccination
Introducing a small/dead/inactive form of a pathogen so the body produces antibodies and memory cells, giving immunity.

Equations

Word and symbol equations — learn both
Magnification = image size ÷ real size
Use with microscope drawings. Convert units (mm → μm, ×1000).
Glucose + Oxygen → CO₂ + Water
Aerobic respiration. Symbol: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
Glucose → Lactic acid
Anaerobic respiration in muscles. Causes oxygen debt.
Glucose → Ethanol + CO₂
Anaerobic respiration in yeast (fermentation).
CO₂ + Water → Glucose + Oxygen
Photosynthesis (light, chlorophyll). Symbol: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
% change = (final − initial) ÷ initial × 100
Osmosis practical. Sign tells you direction (+ = gained, − = lost).
Rate = change ÷ time
General rate formula. Units like cm³/s, bubbles/min etc.
Light intensity ∝ 1/distance²
Inverse square law — double the distance, light is 4× weaker.

Must-Know Extras

Common exam stings · Grade 9 boosters
EX 01

Cell organelles & jobs

Animal vs Plant vs Bacterial
PartFunction
NucleusContains DNA, controls cell
CytoplasmWhere reactions happen
MitochondriaAerobic respiration
RibosomesProtein synthesis
Cell wall (plant)Cellulose, supports cell
ChloroplastsPhotosynthesis
VacuoleStores cell sap, keeps turgid
Plasmid (bact.)Small DNA loop

Bacteria have no nucleus — DNA is a loop in the cytoplasm. They are prokaryotic.

EX 02

The Immune Response

3 lines of defence

Non-specific

  • Skin — physical barrier
  • Stomach acid — kills pathogens in food
  • Cilia + mucus in trachea — trap microbes
  • Tears — contain lysozyme

Specific (white blood cells)

  • Phagocytes engulf pathogens (phagocytosis)
  • Lymphocytes produce antibodies (specific to one antigen)
  • Lymphocytes also make antitoxins (neutralise bacterial toxins)
  • Memory cells remain → faster response on re-infection
EX 03

Drug Development

Pre-clinical → clinical
  1. Pre-clinical: tested on cells, then tissues, then live animals.
  2. Clinical phase 1: low doses on healthy volunteers (safety).
  3. Clinical phase 2/3: on patients to find optimum dose & efficacy.
  4. Double-blind trial: neither doctor nor patient knows who gets drug or placebo — removes bias.
  5. Peer review before publication to detect false claims.

Tests for: toxicity, efficacy, dose.

EX 04

Plant Diseases & Defences

Topic 3 · Infection

Diseases

  • TMV — Tobacco Mosaic Virus → mosaic pattern on leaves, less photosynthesis.
  • Rose black spot — fungus → purple/black spots, leaves drop.
  • Ion deficiency: nitrate → stunted growth; magnesium → chlorosis (yellow leaves).

Plant defences

  • Physical: cellulose cell wall, tough waxy cuticle, layers of dead cells (bark)
  • Chemical: antibacterial chemicals, poisons to deter herbivores
  • Mechanical: thorns, hairs, drooping/curling on touch, mimicry
EX 05

Monoclonal Antibodies

Higher only
  1. Mouse injected with antigen → produces lymphocytes.
  2. Lymphocyte fused with tumour (myeloma) cell → hybridoma.
  3. Hybridoma divides rapidly AND produces antibodies → cloned.
  4. Antibodies collected and purified.

Uses

  • Pregnancy tests (bind to HCG hormone)
  • Diagnosis (detect pathogens, blood clots, cancer)
  • Treating cancer (attach drug/radioactive substance — only kills cancer cells)
EX 06

Communicable Diseases Table

Must memorise
DiseaseTypeSpread
MeaslesVirusDroplets (air)
HIVVirusBody fluids/sex/needles
TMVVirusPlant contact
SalmonellaBacteriumContaminated food
GonorrhoeaBacteriumSTI
Rose black spotFungusWater/wind
MalariaProtistMosquito vector

Required Practicals

Chemistry Paper 1 · 4 practicals
RP 01

Making Soluble Salts

Topic 4 · Chemical changes

Method (CuSO₄ from CuO + H₂SO₄)

  1. Warm dilute sulfuric acid in a beaker.
  2. Add insoluble copper oxide (the base) bit by bit, stirring, until excess remains (acid fully neutralised).
  3. Filter to remove excess CuO.
  4. Evaporate filtrate gently to crystallisation point.
  5. Leave to crystallise → blue copper sulfate crystals.
Don't boil dry — crystals will shatter and contain impurities.
RP 02

Titration

Topic 4 · Higher only

Method

  1. Pipette 25 cm³ of alkali into a conical flask + few drops of indicator (e.g. phenolphthalein — pink in alkali, colourless in acid).
  2. Fill burette with acid; record initial reading at the meniscus.
  3. Add acid slowly, swirling, until indicator just changes colour (end-point).
  4. Record final volume. Repeat until concordant (within 0.10 cm³) titres.
  5. Calculate the mean (ignore the rough trial).

Calculation

Moles = concentration × volume (in dm³). Use ratio from balanced equation.

RP 03

Electrolysis

Topic 4 · Chemical changes

Method

  1. Set up two inert (graphite) electrodes in a beaker of solution (e.g. copper chloride).
  2. Connect to a low-voltage DC power supply.
  3. Observe products at each electrode.

Rules for aqueous solutions

Cathode (−): Hydrogen produced UNLESS metal is less reactive than H (then metal forms).

Anode (+): Oxygen produced UNLESS a halide ion is present (then halogen forms).

OILRIG: Oxidation Is Loss (of electrons), Reduction Is Gain.
RP 04

Temperature change (energy)

Topic 5 · Energy changes

Method

  1. Polystyrene cup inside beaker (insulation), lid with thermometer hole.
  2. Measure 30 cm³ acid, record temperature.
  3. Add 5 cm³ alkali, stir, record max temperature.
  4. Repeat in 5 cm³ steps up to 40 cm³.
  5. Plot temperature change vs volume — peak shows neutralisation point.

Polystyrene cup reduces heat loss to surroundings; lid prevents evaporation losses.

Six-Mark Questions

Full-mark model answers · Chemistry Paper 1
"Describe and explain the trends in Group 1 (alkali metals) reactivity."
6 marks

Model Answer

  1. Group 1 metals (Li, Na, K, Rb, Cs) all have 1 electron in their outer shell.
  2. When they react, they lose this outer electron to form a +1 ion.
  3. Reactivity increases down the group.
  4. This is because the atoms have more electron shells as you go down, so the outer electron is further from the nucleus.
  5. There is also more shielding from inner electrons, reducing the attraction.
  6. So the outer electron is more easily lost in larger atoms → more reactive.
"Compare ionic, covalent and metallic bonding."
6 marks

Model Answer

  1. Ionic bonding occurs between a metal and a non-metal: electrons are transferred, forming +/− ions held by strong electrostatic attraction.
  2. Ionic compounds have high melting points (lots of energy to break bonds) and conduct when molten/dissolved (ions free).
  3. Covalent bonding occurs between non-metals: electrons are shared.
  4. Simple covalent (e.g. CO₂) has low MP — weak intermolecular forces. Giant covalent (e.g. diamond) has very high MP.
  5. Metallic bonding: positive metal ions in a sea of delocalised electrons.
  6. Metals conduct electricity (electrons flow), are malleable (layers slide), and have high melting points.
"Explain how the model of the atom has changed over time."
6 marks

Model Answer

  1. Dalton (early 1800s): atoms are tiny solid spheres, indivisible.
  2. JJ Thomson (1897): discovered the electron via cathode ray experiments → "plum pudding" model: ball of positive charge with electrons embedded.
  3. Rutherford (1911): gold foil/alpha scattering experiment → most α passed through, some deflected, very few bounced back. Concluded most of the atom is empty space with a tiny dense positive nucleus.
  4. Bohr: electrons orbit in fixed shells/energy levels at set distances — explained why atoms were stable.
  5. Chadwick (1932): discovered the neutron, explaining mass that wasn't from protons.
  6. Each model was modified as new experimental evidence emerged — the scientific method.
"Explain the properties of diamond, graphite and graphene in terms of structure and bonding."
6 marks

Model Answer

  1. All three are forms of carbon (allotropes), with strong covalent bonds.
  2. Diamond: each C bonded to 4 others tetrahedrally → giant rigid lattice → very hard, very high MP, doesn't conduct (no free electrons).
  3. Graphite: each C bonded to 3 others in hexagonal layers, with weak forces between layers.
  4. Layers slide → graphite is soft, used as a lubricant.
  5. Each C in graphite has one delocalised electron → conducts electricity (like a metal).
  6. Graphene: a single layer of graphite — one atom thick, extremely strong, good conductor, used in electronics.
"Explain how to extract a metal less reactive than carbon vs more reactive than carbon."
6 marks

Model Answer

  1. Metals are extracted from ores (rocks containing metal compounds, usually oxides).
  2. Extraction depends on the metal's position relative to carbon in the reactivity series.
  3. Metals less reactive than carbon (e.g. iron, zinc, copper) can be extracted by reduction with carbon: e.g. 2Fe₂O₃ + 3C → 4Fe + 3CO₂.
  4. Carbon takes the oxygen — iron oxide is reduced, carbon is oxidised.
  5. Metals more reactive than carbon (e.g. aluminium, sodium) are extracted by electrolysis of the molten compound.
  6. Electrolysis is more expensive because it needs a high temperature (to melt the ore) and a lot of electrical energy.

Key Definitions

Examiner-approved wording
Atom
The smallest part of an element that can exist. Has a nucleus of protons + neutrons, surrounded by electrons in shells.
Element
A substance made of only one type of atom (same number of protons).
Compound
Two or more elements chemically bonded together in fixed ratios.
Isotope
Atoms of the same element (same protons) with different numbers of neutrons.
Mixture
Two or more substances not chemically joined; can be separated by physical means.
Ionic Bond
Electrostatic attraction between oppositely charged ions, formed by transfer of electrons (metal to non-metal).
Covalent Bond
A shared pair of electrons between two non-metal atoms.
Metallic Bond
Electrostatic attraction between positive metal ions and delocalised electrons.
Oxidation
Gain of oxygen OR loss of electrons.
Reduction
Loss of oxygen OR gain of electrons.
Mole (Higher)
The amount of substance containing 6.02 × 10²³ particles (Avogadro's number).
Exothermic
Reaction that releases energy to the surroundings; temperature rises. e.g. combustion, neutralisation.
Endothermic
Reaction that takes in energy from surroundings; temperature falls. e.g. thermal decomposition.
Activation Energy
The minimum energy needed for a reaction to occur.
Electrolysis
Splitting an ionic compound (molten or in solution) using electricity.

Equations & Formulas

Memorise — given equations are minimal
Acid + Metal → Salt + Hydrogen
Universal pattern. Test for H₂: squeaky pop with lit splint.
Acid + Base → Salt + Water
Neutralisation. Base = metal oxide/hydroxide.
Acid + Carbonate → Salt + Water + CO₂
Test for CO₂: turns limewater milky/cloudy.
H⁺ + OH⁻ → H₂O
Ionic equation for neutralisation (Higher).
Moles = mass ÷ Mr
Used in every Higher calculation.
Moles = conc × vol (dm³)
For solutions (titration). 1 dm³ = 1000 cm³.
Concentration = mass ÷ volume
Units g/dm³ (or mol/dm³ if using moles).
% yield = (actual ÷ theoretical) × 100
Real chemistry never reaches 100% — losses, reversibility, side reactions.
Atom economy = (Mr useful product ÷ total Mr) × 100
Measures efficiency — high is greener.

Must-Know Extras

Grade 9 boosters
EX 01

Reactivity Series

Memorise the order

K Na Ca Mg Al (C) Zn Fe (H) Cu Ag Au

"Please Send Cute Monkeys And Cats Zooming Into Hot Coffee Shops And Gardens"

Carbon and hydrogen are non-metals, included for comparison.

  • Above C: needs electrolysis to extract.
  • Below C: extracted by reduction with carbon.
  • Above H: reacts with acids.
EX 02

Periodic Table Trends

Group 1, 7, 0

Group 1 (alkali metals)

React vigorously with water → metal hydroxide + H₂. Reactivity ↑ down group.

Group 7 (halogens)

F, Cl, Br, I. Form −1 ions, diatomic (Cl₂). Reactivity ↓ down group (atom larger → harder to gain electron).

Displacement: more reactive halogen displaces less reactive from its salt. e.g. Cl₂ + 2KBr → 2KCl + Br₂.

Group 0 (noble gases)

Full outer shells → very unreactive. BP increases down group.

EX 03

State Symbols & Balancing

Top exam tip
  • (s) solid · (l) liquid · (g) gas · (aq) aqueous (dissolved in water)

Balancing rules: NEVER change small subscripts (e.g. the 2 in H₂O). Only change big numbers in front. Same number of each atom on both sides.

Example: H₂ + O₂ → H₂O becomes 2H₂ + O₂ → 2H₂O.

EX 04

Tests for Gases

Easy marks
GasTestResult
HydrogenLit splintSqueaky pop
OxygenGlowing splintRelights
CO₂LimewaterCloudy/milky
ChlorineDamp litmusBleached white
EX 05

Energy Profile Diagrams

Exo vs Endo

Exothermic: products lower than reactants (energy released to surroundings).

Endothermic: products higher than reactants (energy absorbed).

Activation energy = the "hump" from reactants to peak. A catalyst lowers Ea by providing an alternative pathway — doesn't change ΔH.

Bond energy calc (Higher): energy change = (bonds broken) − (bonds made). Negative = exothermic.

EX 06

States of Matter & Particle Theory

Topic 2
  • Solid: particles in fixed pattern, vibrating. Strong forces.
  • Liquid: particles close, random, can flow.
  • Gas: particles far apart, fast, random.

Changes: melting/freezing (s↔l), boiling/condensing (l↔g), sublimation (s↔g).

Limitation of model: particles aren't really hard solid spheres, forces vary between substances, particle size is exaggerated.

Required Practicals

Physics Paper 1 · 4 practicals
RP 01

Specific Heat Capacity

Topic 1 · Energy

Method

  1. Measure mass of metal block. Insulate it.
  2. Insert thermometer and immersion heater into the holes.
  3. Record starting temperature.
  4. Switch on heater for set time (e.g. 10 min) using a joulemeter or known power × time.
  5. Record final temperature.

Calculation

E = m × c × ΔT, so c = E ÷ (m × ΔT).

Energy comes from E = Power × time if using a joulemeter or known PSU.

Insulate the block — heat losses make c look bigger than it is.
RP 02

Resistance of a Wire

Topic 2 · Electricity

Method

  1. Set up circuit: battery, ammeter (series), voltmeter (parallel across wire), crocodile clips on metre ruler.
  2. Vary the length of wire (e.g. 10, 20, 30… cm).
  3. For each length, record V and I. Calculate R = V ÷ I.
  4. Plot R against length.

Result

Straight line through origin → resistance is directly proportional to length.

Switch off between readings — current heats the wire, increasing resistance.
RP 03

I-V Characteristics

Topic 2 · Electricity

Method

  1. Use a variable resistor to change current through a component.
  2. Record V and I at each setting (include negative values by reversing battery).
  3. Plot V on x, I on y.

Shapes

  • Fixed resistor: straight line through origin (ohmic).
  • Filament lamp: S-shaped — heats up, resistance rises.
  • Diode: only current in one direction (curve in one quadrant).
RP 04

Density

Topic 3 · Particle Model

Regular shape

  • Mass on balance, volume = l × w × h. Density = m ÷ V.

Irregular shape (eureka can)

  1. Fill eureka can with water to overflow spout.
  2. Place measuring cylinder under spout.
  3. Lower object in gently; displaced water = volume of object.
  4. Mass on balance. Calculate density.

Liquids

Mass of empty cylinder, add liquid, find mass + volume difference.

Six-Mark Questions

Full-mark model answers · Physics Paper 1
"Describe the energy transfers in a coal-fired power station."
6 marks

Model Answer

  1. Coal stores chemical energy. Burning it transfers energy to the thermal store of water in a boiler.
  2. Hot water turns to high-pressure steam.
  3. Steam pushes the blades of a turbine — energy transferred kinetically.
  4. The turbine turns the generator, which transfers energy electrically.
  5. A step-up transformer increases voltage for efficient transmission (less current → less energy lost as heat in wires).
  6. Step-down transformer near homes reduces voltage to a safe level. Some energy is always dissipated to surroundings as wasted thermal energy.
"Compare renewable and non-renewable energy resources."
6 marks

Model Answer

  1. Non-renewable (coal, oil, gas, nuclear) will run out and are being used faster than they form.
  2. Fossil fuels release CO₂ (climate change) and sulfur dioxide (acid rain). Nuclear produces dangerous radioactive waste.
  3. However, they are reliable — always available on demand, high energy output.
  4. Renewable (solar, wind, hydro, geothermal, tidal, biofuel) replenishes naturally and is much cleaner.
  5. Most renewables are unreliable — depend on weather/conditions, often low power output.
  6. The world is moving towards renewables for environmental and ethical reasons, even if costs and reliability are still issues.
Always mention: reliability, cost, environmental impact, energy output.
"Explain how series and parallel circuits differ."
6 marks

Model Answer

  1. In a series circuit, components are on one loop — same current flows through every component.
  2. The total potential difference is shared between components.
  3. Total resistance = sum of resistances (R₁ + R₂ + ...). Adding more components increases resistance, decreases current.
  4. In parallel, components are on separate branches — each gets the same potential difference as the cell.
  5. Current is shared between branches; total current = sum of branch currents.
  6. Adding parallel branches decreases total resistance (more paths for current). Used in homes so each appliance has full mains voltage and can be switched independently.
"Compare contamination and irradiation."
6 marks

Model Answer

  1. Irradiation = being exposed to nuclear radiation from a source.
  2. The object itself does not become radioactive; once removed from the source, the danger ends.
  3. Protect against irradiation with shielding (lead, concrete), distance, and minimising exposure time.
  4. Contamination = radioactive atoms get onto or into an object/person.
  5. Contamination is ongoing — the radioactive material continues to emit radiation, often for a long time.
  6. Alpha is most dangerous if contaminated (highly ionising inside body); gamma is most dangerous as irradiation (penetrates deep).
"Describe the changes when ice is heated to steam in terms of particles and energy."
6 marks

Model Answer

  1. In ice, particles are in a fixed lattice, vibrating with low energy.
  2. As heat is added, particles vibrate more — internal energy rises, temperature rises.
  3. At 0 °C, energy is used to break bonds between particles — temperature stays constant (specific latent heat of fusion). Ice melts to water.
  4. In liquid water, particles can move past each other. Continued heating raises temperature again.
  5. At 100 °C, more energy breaks remaining bonds completely — water boils, temperature constant (specific latent heat of vaporisation).
  6. In steam, particles are far apart and fast moving. Mass is conserved throughout — only arrangement and energy change. Physical change, not chemical.

Key Definitions

Examiner-approved wording
Energy
A quantity that is conserved — never created or destroyed, only transferred between stores.
Power
The rate of energy transfer (or rate of doing work). Units: watts (W) = J/s.
Work Done
Energy transferred when a force moves an object. W = F × d.
Efficiency
The proportion of input energy that is usefully transferred. Useful output ÷ total input. Always < 1.
Specific Heat Capacity
Energy needed to raise 1 kg of a substance by 1 °C. Units: J/kg°C.
Specific Latent Heat
Energy needed to change the state of 1 kg of a substance with no temperature change.
Current
Rate of flow of electric charge. Units: amperes (A) = C/s.
Potential Difference
Energy transferred per unit charge between two points. Units: volts (V) = J/C.
Resistance
Opposition to the flow of current. R = V/I. Units: ohms (Ω).
Density
Mass per unit volume. ρ = m/V. Units kg/m³.
Internal Energy
Total kinetic + potential energy of all particles in a system.
Half-life
The time taken for the number of radioactive nuclei in a sample (or the count rate) to halve.
Alpha (α)
2 protons + 2 neutrons (helium nucleus). Strongly ionising. Stopped by paper or skin.
Beta (β)
High-speed electron from a neutron decay. Moderately ionising. Stopped by ~5 mm aluminium.
Gamma (γ)
High-energy EM wave. Weakly ionising but very penetrating. Stopped only by thick lead/concrete.

Equations & Formulas

★ = must memorise (not given) · ○ = given in equation sheet
★ KE = ½ m v²
Kinetic energy. mass (kg), velocity (m/s) → J.
★ GPE = m g h
Gravitational potential energy. g = 9.8 N/kg on Earth.
★ W = F × d
Work done. Force in line with motion.
★ P = E ÷ t
Power. Also P = W ÷ t.
★ Efficiency = useful ÷ total
As energy OR as power. Multiply by 100 for %.
○ E = m c ΔT
Specific heat capacity. c = J/kg°C.
○ E = m L
Specific latent heat (state change, no temp change).
★ ρ = m ÷ V
Density. kg/m³ or g/cm³.
★ Q = I × t
Charge = current × time. Coulombs.
★ V = I × R
Ohm's law. For ohmic conductors at constant T.
★ P = V × I
Electrical power. Also P = I²R.
★ E = V × Q
Energy transferred. Also E = P × t.
○ E = ½ k e²
Elastic PE (Paper 2, but appears).
In Physics, state the equation → substitute values → answer with units. Each step is a separate mark.

Must-Know Extras

Grade 9 boosters
EX 01

The 8 Energy Stores

Topic 1

Stores: kinetic, thermal, chemical, gravitational, elastic, electrostatic, magnetic, nuclear.

Transfer pathways: mechanically, electrically, by heating, by radiation (light/sound).

Energy is conserved — total stays the same. Wasted energy is usually dissipated as thermal energy to surroundings.

EX 02

National Grid

Topic 2
  • Power stations → step-up transformer → high voltage transmission → step-down → homes (230 V).
  • Higher voltage = lower current, so less energy lost as heat (P_lost = I²R).
  • Live wire: brown, 230 V. Neutral: blue, 0 V. Earth: green/yellow, safety.
  • Earth + fuse: if live touches casing, large current flows to earth, fuse melts, circuit broken.
EX 03

Atomic Model Timeline

Topic 4
  1. Dalton: solid spheres.
  2. Thomson: plum pudding (electrons in positive ball).
  3. Rutherford: alpha scattering → tiny dense nucleus, mostly empty.
  4. Bohr: electrons in fixed shells.
  5. Chadwick: discovered neutrons.

Atom radius ≈ 1 × 10⁻¹⁰ m. Nucleus ≈ 1/10 000 of that.

EX 04

Radiation: Penetration & Ionisation

Topic 4
TypeIonisingStopped byRange in air
AlphaVery highPaper/skin~5 cm
BetaMedium~5 mm Al~1 m
GammaLowThick leadFar
NeutronVariableWater/HFar

Half-life: after each half-life, activity halves. Used for dating, smoke alarms (Am-241), medical tracers.

EX 05

Circuit Symbols (recognise)

Topic 2
  • Cell — long+short line · Battery — multiple cells
  • Switch — gap in line · Fixed resistor — rectangle
  • Variable resistor — rectangle with arrow
  • Ammeter — A in circle (series) · Voltmeter — V in circle (parallel)
  • Diode — triangle with line · LED — diode with arrows out
  • Thermistor — resistance falls as temp rises · LDR — resistance falls as light rises
  • Fuse — rectangle with line through
EX 06

Conservation of Energy & Sankey

Topic 1

Sankey diagram: width of each arrow ∝ energy. Useful out the right, wasted (usually heat) downward.

Reducing waste: lubrication (less friction), insulation (less heat loss), streamlining (less air resistance).

House insulation: loft, cavity walls, double glazing, draught excluders. Thicker / lower thermal conductivity → less heat loss.