[SPEC] How many units does WJEC GCSE The Sciences (Double Award) have?

7 units: Units 1–3 (Year 10, one per discipline), Units 4–6 (Year 11, one per discipline), Unit 7 (Scientific Enquiry, sat in Year 11 spring term)

[SPEC] What does Unit 7 assess?

Scientific enquiry: learners complete 2 enquiries chosen from 3 (one each in biology, chemistry and physics). Each enquiry = 1-hour practical task + 1-hour written task.

[SPEC] What percentage of the qualification is Unit 7 worth?

10%

[SPEC] What are the two tiers in the new GCSE The Sciences Double Award?

Higher (A*–D) and Foundation (C–G). Learners may be entered at different tiers across units.

[SPEC] What are the paired grades used in the new science double award?

A*A*, AA, BB, CC, DD, EE, FF, GG. No mixed grades (no AB, BC, CD etc.).

[SPEC] When must 55% of the qualification be taken to meet the terminal rule?

In Year 11 — achieved by entering Units 4, 5, 6 and 7 in the final year.

[SPEC] What are the three assessment objectives and their weightings in The Sciences?

AO1 (knowledge and understanding) 25%; AO2 (apply knowledge) 50%; AO3 (analyse, interpret, evaluate) 25%

[SPEC] What replaced prescribed required practicals in the new science spec?

There are no prescribed required practicals. Practical skills (SE1–SE8) are embedded throughout all units and formally assessed in Unit 7.

[SPEC] What are the 6 discipline exam units and their titles?

Unit 1: Biology – Basis of Life; Unit 2: Chemistry – Chemical Substances and How They Behave; Unit 3: Physics – Forces, Motion and the Universe; Unit 4: Biology – Continuity of Life; Unit 5: Chemistry – Chemical Bonding, Reactions and Resources; Unit 6: Physics – Waves, Electricity and Energy

[SPEC] What is the 'making connections' feature in Units 4–6?

Each Year 11 paper (Units 4–6) includes 8 marks of questions that link back to the corresponding Year 10 unit (e.g. Unit 6 links to Unit 3). 25% of marks are common across Higher and Foundation.

[U1-BIO] What three types of cell are studied in GCSE biology?

Animal cells, plant cells, and bacterial (prokaryotic) cells

[U1-BIO] Name the structures found in a plant cell but NOT in an animal cell

Cell wall (cellulose), chloroplasts, large permanent vacuole

[U1-BIO] What is the function of mitochondria?

Site of aerobic respiration — releases energy (as ATP) from glucose

[U1-BIO] What is the function of ribosomes?

Site of protein synthesis

[U1-BIO] What is the function of the cell membrane?

Controls what enters and leaves the cell; partially permeable barrier

[U1-BIO] Define diffusion

Net movement of particles from an area of high concentration to low concentration, down a concentration gradient. Passive — requires no energy.

[U1-BIO] Define osmosis

Net movement of water molecules through a partially permeable membrane from a region of higher water potential (dilute solution) to lower water potential (concentrated solution). Passive.

[U1-BIO] Define active transport

Movement of substances against a concentration gradient (low to high) using energy (ATP) from respiration. Requires carrier proteins.

[U1-BIO] What is the word equation for aerobic respiration?

Glucose + oxygen → carbon dioxide + water (+ energy/ATP)

[U1-BIO] What is the word equation for anaerobic respiration in animals?

Glucose → lactic acid (+ small amount of energy)

[U1-BIO] What is the word equation for anaerobic respiration in yeast?

Glucose → ethanol + carbon dioxide (+ small amount of energy)

[U1-BIO] What is the word equation for photosynthesis?

Carbon dioxide + water → glucose + oxygen (using light energy, in chloroplasts)

[U1-BIO] What factors limit the rate of photosynthesis?

Light intensity, CO2 concentration, temperature, and water availability

[U1-BIO] What is an enzyme?

A biological catalyst (protein) that speeds up a chemical reaction without being used up; specific to one substrate due to its active site shape

[U1-BIO] Explain the lock and key model of enzyme action

The substrate fits into the enzyme's complementary active site, forming an enzyme-substrate complex. Products are released and the enzyme is unchanged.

[U1-BIO] What happens to an enzyme above its optimum temperature?

It denatures — the active site changes shape permanently, so the substrate can no longer bind

[U1-BIO] Name the main digestive enzymes and their substrates

Amylase: starch → sugars. Protease: proteins → amino acids. Lipase: fats → fatty acids + glycerol.

[U1-BIO] What is the difference between a tissue and an organ?

Tissue: a group of similar cells performing a specific function. Organ: a group of different tissues working together to perform a function.

[U1-BIO] Describe the structure of the heart

Four-chambered muscular pump. Right side pumps deoxygenated blood to lungs; left side pumps oxygenated blood to body. Valves prevent backflow.

[U1-BIO] What is the difference between arteries, veins and capillaries?

Arteries: thick muscular walls, carry blood away from heart at high pressure. Veins: thinner walls with valves, carry blood to heart. Capillaries: one cell thick, site of exchange with tissues.

[U1-BIO] What structures in the lungs are adapted for gas exchange?

Alveoli — tiny air sacs with large surface area, thin walls, moist lining, and rich blood supply. O2 diffuses in, CO2 diffuses out.

[U1-BIO] What is the role of haemoglobin?

Protein in red blood cells that binds oxygen in the lungs and releases it at respiring tissues

[U1-BIO] What is a pathogen?

A microorganism (bacterium, virus, fungus or protist) that causes disease

[U2-CHEM] What are the three subatomic particles and their charges?

Proton (+1, in nucleus), neutron (0, in nucleus), electron (−1, in shells around nucleus)

[U2-CHEM] What is atomic number?

The number of protons in an atom's nucleus (also equals the number of electrons in a neutral atom)

[U2-CHEM] What is mass number?

Total number of protons + neutrons in the nucleus

[U2-CHEM] What are isotopes?

Atoms of the same element with the same number of protons but different numbers of neutrons, giving different mass numbers

[U2-CHEM] How is the periodic table organised?

Elements in order of increasing atomic number. Vertical columns = groups (same number of outer electrons, similar properties). Horizontal rows = periods.

[U2-CHEM] What are the properties of Group 1 (alkali metals)?

Soft metals, low density, react vigorously with water producing hydrogen and a metal hydroxide. Reactivity increases down the group.

[U2-CHEM] What are the properties of Group 7 (halogens)?

Non-metals, diatomic molecules, form salts with metals. Reactivity decreases down the group.

[U2-CHEM] What are the properties of Group 0 (noble gases)?

Colourless gases, full outer electron shells, very unreactive. Used in lighting (neon signs) and as inert atmospheres.

[U2-CHEM] What is the difference between an element, a compound and a mixture?

Element: one type of atom only. Compound: two or more elements chemically bonded in a fixed ratio. Mixture: two or more substances not chemically combined; separable by physical methods.

[U2-CHEM] Name five methods of separating mixtures

Filtration, evaporation/crystallisation, simple distillation, fractional distillation, chromatography

[U2-CHEM] State the law of conservation of mass

In a chemical reaction the total mass of reactants equals the total mass of products. Atoms are not created or destroyed.

[U2-CHEM] What is the difference between exothermic and endothermic reactions?

Exothermic: releases energy to surroundings (temperature rises); e.g. combustion, neutralisation. Endothermic: absorbs energy from surroundings (temperature falls); e.g. thermal decomposition.

[U2-CHEM] What is a neutralisation reaction?

Acid + alkali → salt + water. The reaction between H+ ions and OH− ions to form water.

[U2-CHEM] What does the pH scale measure?

Acidity/alkalinity on a 0–14 scale: 0–6 = acidic, 7 = neutral, 8–14 = alkaline. Each unit represents a 10× change in H+ concentration.

[U2-CHEM] What happens when a metal reacts with an acid?

Single displacement reaction: metal + acid → salt + hydrogen gas. More reactive metals react faster.

[U2-CHEM] Name four factors that increase the rate of a chemical reaction

Increasing temperature, increasing concentration (or pressure for gases), increasing surface area, adding a catalyst

[U2-CHEM] What is a catalyst?

A substance that increases the rate of a reaction without being used up. Lowers the activation energy.

[U2-CHEM] How do you test for hydrogen gas?

Hold a lit splint near the gas — a 'squeaky pop' confirms hydrogen

[U2-CHEM] How do you test for carbon dioxide?

Bubble through limewater — turns cloudy/milky (calcium carbonate precipitate forms)

[U2-CHEM] How do you test for oxygen?

A glowing splint relights in the presence of oxygen

[U2-CHEM] Define oxidation and reduction (in terms of oxygen)

Oxidation: gain of oxygen. Reduction: loss of oxygen. OIL RIG (Oxidation Is Loss, Reduction Is Gain — of electrons).

[U2-CHEM] What is a displacement reaction?

A more reactive element displaces a less reactive element from its compound; e.g. Fe + CuSO4 → FeSO4 + Cu

[U2-CHEM] Give the reactivity series of metals in order (most to least reactive)

K, Na, Li, Ca, Mg, Al, (C), Zn, Fe, Sn, Pb, (H), Cu, Ag, Au, Pt

[U2-CHEM] What is relative formula mass (Mr)?

The sum of all relative atomic masses (Ar) of atoms in one formula unit of a substance

[U3-PHYS] What is the difference between speed and velocity?

Speed is scalar (magnitude only). Velocity is a vector (magnitude and direction). Both measured in m/s.

[U3-PHYS] What is the equation for speed?

Speed (m/s) = distance (m) ÷ time (s)

[U3-PHYS] What is acceleration and what is its equation?

Rate of change of velocity. Acceleration (m/s²) = change in velocity (m/s) ÷ time (s)

[U3-PHYS] What does a distance–time graph show?

Gradient = speed. Flat line = stationary. Steeper gradient = faster. Curve upward = accelerating.

[U3-PHYS] What does a velocity–time graph show?

Gradient = acceleration. Flat line = constant velocity. Area under graph = distance travelled.

[U3-PHYS] State Newton's First Law of Motion

An object remains at rest or moves at constant velocity unless acted upon by a resultant (unbalanced) force

[U3-PHYS] State Newton's Second Law of Motion

F = ma. Resultant force (N) = mass (kg) × acceleration (m/s²)

[U3-PHYS] State Newton's Third Law of Motion

Every action has an equal and opposite reaction. Forces act on different objects.

[U3-PHYS] What is the difference between mass and weight?

Mass: amount of matter in kg (same everywhere). Weight: gravitational force on that mass in N. W = m × g (g ≈ 10 N/kg on Earth).

[U3-PHYS] What is terminal velocity?

The constant maximum velocity reached when the driving force equals drag/resistive force. Resultant force = 0, so acceleration = 0.

[U3-PHYS] What is the equation for momentum?

p = mv. Momentum (kg m/s) = mass (kg) × velocity (m/s)

[U3-PHYS] State the law of conservation of momentum

In a closed system, total momentum before a collision = total momentum after, provided no external forces act

[U3-PHYS] What is the equation for work done?

W = Fd. Work done (J) = force (N) × distance moved in the direction of the force (m)

[U3-PHYS] What is the equation for gravitational potential energy?

GPE (J) = mass (kg) × gravitational field strength (N/kg) × height (m); GPE = mgh

[U3-PHYS] What is the equation for kinetic energy?

KE (J) = ½ × mass (kg) × velocity² (m/s)²; KE = ½mv²

[U3-PHYS] What is pressure and its equation?

Pressure (Pa) = force (N) ÷ area (m²)

[U3-PHYS] Describe the structure of the Solar System

Sun at the centre; 8 planets orbiting in ellipses (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune); also moons, asteroids and comets

[U3-PHYS] What is a light year?

The distance light travels in one year (≈ 9.46 × 10¹⁵ m). Used for distances between stars and galaxies.

[U3-PHYS] What is the Big Bang theory?

The universe began ~13.8 billion years ago from an extremely hot, dense point and has been expanding ever since. Supported by cosmic microwave background radiation and red-shift of distant galaxies.

[U3-PHYS] What is red-shift and what does it tell us?

Observed increase in wavelength (shift toward red end of spectrum) of light from distant galaxies, indicating they are moving away from us. Evidence that the universe is expanding.

[U3-PHYS] What is the life cycle of a star like our Sun?

Nebula → protostar → main sequence star → red giant → planetary nebula → white dwarf → (eventually) black dwarf

[U3-PHYS] What is the life cycle of a massive star?

Nebula → protostar → main sequence star → red supergiant → supernova → neutron star or black hole

[U4-BIO] What is the structure of DNA?

Double helix. Two strands of nucleotides, each containing deoxyribose sugar, a phosphate group, and a base (A, T, C or G). Base pairs: A-T and C-G.

[U4-BIO] What is a gene?

A section of DNA that codes for the production of a specific protein

[U4-BIO] How many chromosomes do human body cells have?

46 (23 pairs). Gametes (sperm and egg cells) have 23 (haploid).

[U4-BIO] What is the difference between mitosis and meiosis?

Mitosis: division for growth and repair; produces 2 genetically identical diploid daughter cells. Meiosis: division for sexual reproduction; produces 4 genetically varied haploid gametes.

[U4-BIO] What is the difference between genotype and phenotype?

Genotype: the allele combination an organism has. Phenotype: the observable characteristic expressed.

[U4-BIO] What is the difference between dominant and recessive alleles?

Dominant: expressed whenever present (one or two copies). Recessive: only expressed when two copies are present (homozygous recessive).

[U4-BIO] What do homozygous and heterozygous mean?

Homozygous: both alleles are identical (e.g. BB or bb). Heterozygous: alleles differ (e.g. Bb).

[U4-BIO] What is natural selection?

Process by which organisms with advantageous inherited variations survive and reproduce more, passing those traits to offspring. Over generations, beneficial allele frequencies increase in the population.

[U4-BIO] What is a mutation?

A random change in the DNA base sequence. Can alter the protein produced. Most are neutral; some harmful; rarely beneficial.

[U4-BIO] What is an ecosystem?

All living organisms (the community) in an area together with the non-living environment they interact with

[U4-BIO] What is a food chain and what does it show?

Shows feeding relationships and the direction of energy flow between organisms. Starts with a producer (plant). E.g. grass → rabbit → fox.

[U4-BIO] What is the difference between a producer and a consumer?

Producer: makes its own food by photosynthesis (plant). Consumer: obtains energy by eating other organisms (primary = eats plants; secondary = eats primary consumers).

[U4-BIO] What are decomposers and what do they do?

Bacteria and fungi that break down dead organic material, returning nutrients (e.g. nitrates) to the soil

[U4-BIO] What is biodiversity?

The variety of living organisms in an area, including species diversity, genetic diversity within species, and variety of habitats

[U4-BIO] Name the main human threats to biodiversity

Habitat destruction, pollution, overhunting/overfishing, invasive species introductions, climate change

[U4-BIO] What is homeostasis?

The maintenance of a stable internal environment (e.g. blood glucose, body temperature, water balance) despite changes in external conditions

[U4-BIO] How does the body regulate blood glucose levels?

High glucose: pancreas releases insulin → liver stores excess as glycogen. Low glucose: pancreas releases glucagon → liver converts glycogen back to glucose.

[U4-BIO] What does ADH do in water balance?

Antidiuretic hormone (from pituitary gland) causes kidneys to reabsorb more water when dehydrated → less, more concentrated urine is produced

[U4-BIO] Outline the key stages of the nitrogen cycle

Decomposition → ammonification → nitrification (nitrifying bacteria produce nitrates) → absorption by plants. Denitrifying bacteria return N2 to atmosphere. Nitrogen fixation (lightning or bacteria) adds N2 to soil.

[U4-BIO] What is the enhanced greenhouse effect and how does it relate to climate change?

Greenhouse gases (CO2, methane, water vapour) absorb outgoing IR radiation and re-emit it, warming Earth. Human emissions (fossil fuels, deforestation, agriculture) enhance this effect, causing global warming and climate change.

[U4-BIO] Give three impacts of climate change on ecosystems

Species range shifts; changes in migration and breeding timing; coral bleaching; increased extinction rates; sea-level rise threatening coastal habitats

[U5-CHEM] What is ionic bonding?

Transfer of one or more electrons from a metal atom to a non-metal atom. Produces oppositely charged ions held in a giant ionic lattice by electrostatic attraction.

[U5-CHEM] What are the properties of ionic compounds?

High melting/boiling points; conduct electricity when dissolved in water or molten (ions free to move); brittle; many are soluble in water.

[U5-CHEM] What is covalent bonding?

The sharing of a pair of electrons between two non-metal atoms. Each shared pair = one covalent bond.

[U5-CHEM] What is the difference between simple molecular and giant covalent structures?

Simple molecular (e.g. H2O, CO2): low m.p./b.p., usually gases or liquids at room temperature, don't conduct electricity. Giant covalent (e.g. diamond, graphite, SiO2): very high m.p./b.p., very hard (except graphite).

[U5-CHEM] Why does graphite conduct electricity?

Each carbon atom forms only 3 covalent bonds, leaving one delocalised electron per atom free to move through the structure and carry charge

[U5-CHEM] What is metallic bonding?

A lattice of positive metal ions (cations) surrounded by a 'sea' of delocalised electrons; strong electrostatic attraction between the two holds the structure together

[U5-CHEM] Why are metals good conductors of heat and electricity?

Delocalised electrons in the metallic structure are free to move, transferring energy and carrying charge throughout the material

[U5-CHEM] What is electrolysis?

Decomposition of an ionic compound (when molten or dissolved) by passing electricity through it. Cations move to cathode (−); anions move to anode (+).

[U5-CHEM] What are the products of electrolysis of brine?

Hydrogen gas at cathode, chlorine gas at anode, sodium hydroxide solution remains. Important industrial process (chlor-alkali industry).

[U5-CHEM] What is an alkane? Give four examples.

Saturated hydrocarbon. General formula CnH2n+2. All C-C single bonds. Examples: methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10).

[U5-CHEM] What is an alkene? Give an example.

Unsaturated hydrocarbon with at least one C=C double bond. General formula CnH2n. More reactive than alkanes. Example: ethene (C2H4).

[U5-CHEM] How do you test for an alkene?

Add bromine water. An alkene decolourises it (addition reaction across the double bond). An alkane leaves it orange/brown.

[U5-CHEM] What is cracking?

Thermal (or catalytic) decomposition of long-chain hydrocarbons from crude oil into shorter, more useful molecules including alkenes. Important for producing fuels and monomers.

[U5-CHEM] What is addition polymerisation?

Many small alkene monomers join through their double bonds to form a long polymer chain with no atoms lost. E.g. ethene → poly(ethene).

[U5-CHEM] What are the main fractions from fractional distillation of crude oil, in order of increasing boiling point?

Refinery gases → petrol → naphtha → kerosene → diesel → fuel oil → bitumen

[U5-CHEM] What are the conditions for the Haber process?

N2 + 3H2 ⇌ 2NH3. Conditions: ~450°C, ~200 atm, iron catalyst. A compromise between reaction rate and yield.

[U5-CHEM] What does sustainability mean in a chemistry context?

Using chemical resources in ways that meet current needs without compromising future generations' ability to meet theirs; includes reducing waste, recycling, and using renewable feedstocks (green chemistry principles)

[U5-CHEM] How is drinking water treated?

Screening (remove large debris) → sedimentation (particles settle) → filtration through sand/gravel → chlorination (kills microorganisms). Desalination used for seawater.

[U5-CHEM] How can agricultural fertilisers cause water pollution?

Excess nitrates and phosphates leach from farmland into waterways → eutrophication: algal bloom → algae die → bacteria decompose algae using dissolved O2 → fish and other aquatic life die from lack of oxygen

[U5-CHEM] What is the difference between empirical formula, molecular formula and structural formula?

Empirical: simplest whole-number ratio of atoms (e.g. CH2). Molecular: actual number of atoms in one molecule (e.g. C2H4). Structural: shows arrangement/connectivity of atoms.

[U6-PHYS] What is a wave?

A transfer of energy through a medium (or vacuum) without permanent transfer of matter. The medium oscillates as the wave passes.

[U6-PHYS] What is the difference between transverse and longitudinal waves?

Transverse: oscillation perpendicular to direction of travel (e.g. light, water waves). Longitudinal: oscillation parallel to direction of travel, creating compressions and rarefactions (e.g. sound).

[U6-PHYS] Define amplitude, wavelength, frequency and period

Amplitude: maximum displacement from equilibrium. Wavelength (λ): distance between two adjacent crests. Frequency (f): waves per second (Hz). Period (T): time for one complete wave; T = 1/f.

[U6-PHYS] What is the wave equation?

v = fλ. Wave speed (m/s) = frequency (Hz) × wavelength (m)

[U6-PHYS] What is the speed of all electromagnetic waves in a vacuum?

3 × 10⁸ m/s

[U6-PHYS] List the electromagnetic spectrum from lowest to highest frequency

Radio waves → microwaves → infrared → visible light → ultraviolet → X-rays → gamma rays

[U6-PHYS] What are uses and hazards of ultraviolet radiation?

Uses: sterilisation, fluorescent lamps. Hazards: causes skin cancer, cataracts; burns skin. Ozone layer absorbs most UV from the Sun.

[U6-PHYS] What are uses and hazards of X-rays?

Uses: medical imaging (bones), airport security. Hazards: ionising radiation — can damage DNA and cause cancer; exposure should be minimised.

[U6-PHYS] State the law of reflection

Angle of incidence = angle of reflection (both measured from the normal to the surface)

[U6-PHYS] What is refraction?

The change in speed (and usually direction) of a wave as it crosses a boundary between two different media. Light slows and bends toward the normal entering a denser medium.

[U6-PHYS] What is total internal reflection?

When light travels from a denser to a less dense medium and hits the boundary at an angle greater than the critical angle, all light is reflected back. Basis of optical fibres and endoscopes.

[U6-PHYS] State Ohm's Law and its equation

Current through an ohmic conductor is proportional to voltage (at constant temperature). V = IR. Voltage (V) = current (A) × resistance (Ω).

[U6-PHYS] What is the difference between series and parallel circuits?

Series: single loop; same current throughout; voltages add up. Parallel: separate branches; same voltage across each branch; currents add up.

[U6-PHYS] What is electrical power and its equation?

P = IV. Power (W) = current (A) × voltage (V). Also P = I²R.

[U6-PHYS] What is the difference between AC and DC?

DC: direct current flows in one direction (e.g. batteries). AC: alternating current reverses direction periodically (mains supply in UK = 230 V, 50 Hz).

[U6-PHYS] What is electromagnetic induction?

A changing magnetic field through a conductor induces an EMF (and current) in that conductor. Basis for generators and transformers.

[U6-PHYS] What is the transformer equation?

Vp/Vs = Np/Ns (ratio of voltages = ratio of turns). For an ideal transformer: power in = power out, so VpIp = VsIs.

[U6-PHYS] Why are power lines operated at high voltage?

High voltage → low current for the same power (P = IV) → less energy wasted as heat in cables (P = I²R). Step-up transformers increase voltage for transmission; step-down reduce it for consumers.

[U6-PHYS] What is specific heat capacity?

The energy needed to raise the temperature of 1 kg of a substance by 1°C. Q = mcΔT (energy = mass × specific heat capacity × temperature change).

[U6-PHYS] What is efficiency and how is it calculated?

Useful energy (or power) output ÷ total energy (or power) input. Often expressed as a percentage. An efficiency of 1 (or 100%) means no energy is wasted.

[U6-PHYS] What is the difference between renewable and non-renewable energy resources?

Non-renewable (fossil fuels, nuclear): finite supply, will eventually run out. Renewable (solar, wind, hydro, tidal, geothermal, biomass): replenished naturally; generally much lower carbon emissions.

[U6-PHYS] What are the advantages and disadvantages of nuclear power?

Advantages: very low CO2 emissions, reliable base-load, high energy density. Disadvantages: long-lived radioactive waste, risk of accidents, very high build costs, uranium mining impacts.

[U6-PHYS] What is static electricity and how does it arise?

A build-up of electric charge on an insulating surface. Caused by friction transferring electrons from one material to another. Like charges repel; opposite charges attract.

[U6-PHYS] What is the difference between alpha, beta and gamma radiation?

Alpha (α): helium nucleus (2p+2n); most ionising; stopped by paper or a few cm of air. Beta (β): fast electron from nucleus; moderately ionising; stopped by a few mm of aluminium. Gamma (γ): high-energy EM wave; least ionising; needs thick lead or concrete to reduce it significantly.

[U7-SE] What are the 8 scientific enquiry skill areas (SE1–SE8)?

SE1: Identify and research. SE2: Plan. SE3: Predict. SE4: Carry out. SE5: Record and present. SE6: Analyse. SE7: Conclude. SE8: Evaluate.

[U7-SE] What is the difference between independent, dependent and control variables?

Independent: variable you deliberately change. Dependent: variable you measure in response. Control: all other variables kept constant to ensure a fair test.

[U7-SE] What is a good scientific hypothesis?

A testable, specific prediction based on scientific knowledge; states a relationship between the independent and dependent variables and gives a reason for it.

[U7-SE] What is the difference between accuracy and precision?

Accuracy: how close a result is to the true value. Precision: how repeatable/reproducible the results are (close to each other), regardless of whether they are accurate.

[U7-SE] What is the difference between systematic and random errors?

Systematic: consistent error in the same direction (e.g. zero error on a balance); affects accuracy. Random: unpredictable variation; affects precision; reduced by repeating and averaging.

[U7-SE] What is an anomalous result?

A data point that does not fit the overall pattern of results. Should be identified, investigated, and usually excluded from mean calculations.

[U7-SE] When should you use a line graph rather than a bar chart?

Line graph: both variables are continuous (e.g. temperature over time). Bar chart: independent variable is categoric (e.g. different types of metal).

[U7-SE] What does a 'valid' investigation mean?

It actually tests what it claims to test — the correct dependent variable is measured and all other relevant variables are controlled.

[U7-SE] What does 'reliable' mean in a scientific enquiry?

Results are consistent and reproducible when the investigation is repeated under the same conditions. Improved by repeating measurements and comparing results.

[U7-SE] How do you calculate percentage error?

Percentage error (%) = (uncertainty ÷ measured value) × 100. Indicates the reliability of a single measurement.