Contents
1 · Syllabus Overview
Combined Physics–Chemistry (CPC) is offered as 5105 (Science — Physics, Chemistry) or 5131 (Science — Chemistry, Physics). This combination is the most calculation-heavy of the Combined Science pathways — strong numeracy and formula recall are essential for success in Paper 2.
Whereas Combined Bio–Chem rewards biological vocabulary and mechanism explanations, Combined Phy–Chem rewards accurate calculation, precise formula use, and the ability to convert and manipulate physical quantities with correct units. Losing a unit in any answer typically costs a mark.
2 · Physics Topics In Depth
Measurement and Kinematics
SI units, scalar vs vector quantities. Displacement, velocity (v = s/t), acceleration (a = Δv/t). Distance-time and velocity-time graphs — gradient = velocity or acceleration, area under v-t graph = displacement. Equations of motion for uniform acceleration.
A car accelerates from rest to 20 m/s in 4 s, then travels at constant speed for 6 s. Calculate the total distance travelled.
Distance during acceleration = area of triangle = ½ × 4 × 20 = 40 m
Distance at constant speed = 20 × 6 = 120 m
Total = 40 + 120 = 160 m
Forces and Newton's Laws
Newton 1: An object continues at rest or constant velocity unless acted upon by a resultant force. Newton 2: F = ma (resultant force = mass × acceleration). Newton 3: Every action has an equal and opposite reaction. Weight W = mg. Friction, normal force, tension. Free-body diagrams.
Energy, Work, and Power
Work done W = Fd (when force and displacement are in the same direction). Kinetic energy KE = ½mv². Gravitational potential energy GPE = mgh. Conservation of energy. Power P = W/t = Fv. Efficiency = (useful energy output / total energy input) × 100%.
Efficiency must always be ≤ 100% and expressed either as a decimal (0.75) or percentage (75%). A machine with 75% efficiency converts 75 J of every 100 J input into useful output — 25 J is wasted, usually as heat.
Thermal Physics
Specific heat capacity: Q = mcΔT (energy = mass × SHC × temperature change). Specific latent heat: Q = mL (energy absorbed/released during a change of state at constant temperature). Thermal expansion. Methods of heat transfer: conduction, convection, radiation.
Waves and Light
Wave speed v = fλ (speed = frequency × wavelength). Reflection (angle of incidence = angle of reflection). Refraction (bending of waves at boundaries; light slows and bends toward normal when entering denser medium). Total internal reflection. Converging lens: focal length, real/virtual images, ray diagrams.
Electricity
Ohm's Law: V = IR. Series circuits: R_total = R₁ + R₂, same current throughout. Parallel circuits: 1/R_total = 1/R₁ + 1/R₂, same voltage across branches. Power: P = IV = I²R = V²/R. Energy: E = Pt = IVt. Domestic electricity safety (fuses, earthing, circuit breakers).
Electromagnetism
Force on a current-carrying conductor in a magnetic field: F = BIL. Fleming's Left-Hand Rule (motor effect). Electromagnetic induction: changing magnetic flux induces e.m.f. Fleming's Right-Hand Rule (generator effect). Transformers: Vp/Vs = Np/Ns; VpIp = VsIs (ideal). See our full Electromagnetism notes.
Radioactivity
Alpha (α): helium nucleus, charge +2, stopped by paper. Beta (β): fast electron, charge −1, stopped by aluminium. Gamma (γ): electromagnetic radiation, charge 0, reduced by thick lead. Half-life: time for radioactive nuclei to halve. Nuclear equations — conservation of mass number and atomic number.
3 · Chemistry Topics In Depth
Atomic Structure and the Periodic Table
Proton number (atomic number), nucleon number (mass number), electronic configuration. Periods and groups — group number = electrons in outer shell; period number = number of electron shells. Isotopes (same protons, different neutrons). Relative atomic mass.
Bonding and Structure
Ionic bonding: metal + non-metal, electron transfer, forms giant ionic lattice. High melting point, conducts when molten or in solution. Covalent bonding: non-metal + non-metal, electron sharing. Simple molecular (low m.p., poor conductor); giant covalent (e.g. diamond — very high m.p.). Metallic bonding: sea of delocalised electrons — conducts electricity and heat, malleable.
Stoichiometry and Mole Calculations
Mole = 6.02 × 10²³ particles (Avogadro's number). n = m/Mr (moles = mass / relative formula mass). For gases at RTP: 1 mol = 24 dm³. For solutions: n = c × V (concentration × volume). Reacting masses from balanced equations.
How many grams of CO₂ are produced when 6 g of carbon is burned completely? (C = 12, O = 16)
Equation: C + O₂ → CO₂
Moles of C = 6/12 = 0.5 mol → 0.5 mol CO₂ → mass = 0.5 × 44 = 22 g CO₂
Acids, Bases, and Salts
Acids produce H⁺(aq); bases produce OH⁻(aq). Neutralisation: H⁺ + OH⁻ → H₂O. pH: 0–6 acidic, 7 neutral, 8–14 alkaline. Salt preparation: titration (soluble salts), precipitation (insoluble salts), direct synthesis. Ionic equations — remove spectator ions.
Metals and Reactivity
Reactivity series (K, Na, Ca, Mg, Al, Zn, Fe, Sn, Pb, H, Cu, Ag, Au). Reactions of metals with water, acid, oxygen. Displacement reactions. Extraction of metals (electrolysis for reactive metals like Al; carbon reduction for moderately reactive metals like Fe in the blast furnace).
Organic Chemistry
Hydrocarbons: alkanes (saturated, CₙH₂ₙ₊₂), alkenes (unsaturated, CₙH₂ₙ — test: decolourises bromine water). Alcohols: fermentation, combustion, uses. Carboxylic acids: weak acids. Esters (from alcohol + carboxylic acid — used in perfumes and food flavourings). Addition polymerisation of alkenes (e.g. poly(ethene)).
4 · Key Formulas — Physics & Chemistry
| Formula | Meaning | Subject |
|---|---|---|
| v = s/t | Speed = distance / time | Physics |
| F = ma | Force = mass × acceleration | Physics |
| W = Fd | Work done = force × distance | Physics |
| KE = ½mv² | Kinetic energy | Physics |
| GPE = mgh | Gravitational potential energy | Physics |
| P = IV | Electrical power = current × voltage | Physics |
| V = IR | Ohm's Law | Physics |
| Q = mcΔT | Thermal energy transfer | Physics |
| v = fλ | Wave speed = frequency × wavelength | Physics |
| Vp/Vs = Np/Ns | Transformer voltage/turns ratio | Physics |
| n = m/Mr | Moles = mass / relative formula mass | Chemistry |
| n = cV | Moles = concentration × volume | Chemistry |
5 · Cross-Discipline Links
| Physics concept | Chemistry connection |
|---|---|
| Electrical energy (E = IVt) | Energy changes in chemical reactions (joules as common unit) |
| Heat transfer (conduction, convection) | Exothermic and endothermic reactions release/absorb heat |
| Pressure and kinetic particle theory | Gas laws and the effect of pressure on reaction rate and equilibrium |
| Radioactive decay and half-life | Nuclear equations, isotopes, nuclear fission |
| Wave energy (UV, X-ray, gamma) | Types of nuclear radiation; electromagnetic spectrum |
6 · Calculation Technique Tips
1 — Write the formula. Even if you know it, write it down. 2 — Substitute the values. Include units at this step. 3 — Calculate. Show the arithmetic. 4 — State the answer with units. Never leave a physical answer without a unit.
Common traps: km/h vs m/s (÷3.6), kJ vs J (×1000), cm³ vs dm³ (÷1000), g vs kg (÷1000), nm vs m (×10⁻⁹). Always check which unit the question gives and which it asks for.
🎯 Practice Quiz — Test Yourself
8 O-Level-style questions on this topic. Select an answer to see instant feedback.