IGCSE Physics — Practice Paper 1

Motion, forces, energy, thermal physics, waves and electricity. Cambridge marks against command words, so each solution names the command word and shows what that word requires.

How to use this: before writing anything, underline the command word. State wants one line. Describe wants what happens. Explain wants why. Answering the wrong command word is the most common way to lose marks you knew.

Section A

1. State the difference between speed and velocity (2 marks)

• Speed is a scalar — magnitude only
• Velocity is a vector — magnitude and direction

Command word — State: a short factual answer. No explanation required, and none is credited.

Where the marks sit: 1 for scalar/vector, 1 for the mention of direction.

2. A car accelerates uniformly from rest to $20\ \text{m/s}$ in $8.0\ \text{s}$. Calculate its acceleration (2 marks)

        Δv      v - u      20 - 0
a  =  ------ = -------- = --------  =  2.5 m/s²
        Δt        t          8.0

Where the marks sit: 1 for the correct equation with substitution, 1 for the answer with units.

Note: "from rest" means $u = 0$. Cambridge states initial conditions in words rather than symbols, so read for them.

3. Describe an experiment to determine the density of an irregularly shaped stone (4 marks)

1. Measure the mass of the stone using a balance, recording it in grams
2. Part-fill a measuring cylinder with water and record the initial volume $V_1$
3. Lower the stone in using a thread until fully submerged, and record the new volume $V_2$
4. The volume of the stone is $V_2 - V_1$; calculate density using $\rho = m / V$

Command word — Describe: a sequence of steps someone else could follow. Each measurement needs the instrument named.

Where the marks sit: 1 for measuring mass, 1 for initial volume, 1 for displacement giving $V_2 - V_1$, 1 for the density calculation.

Common mistake: omitting fully submerged. If part of the stone is above the water the displaced volume is wrong, and Cambridge awards a mark for that detail.

4. Explain why a metal spoon feels colder than a wooden spoon at the same temperature (3 marks)

1. Metal is a better thermal conductor than wood
2. It therefore conducts thermal energy away from your hand more quickly
3. Your hand detects the rate of energy loss, not temperature itself, so the metal feels colder even though both are at the same temperature

Command word — Explain: requires the reason, and here the third point is the actual explanation. An answer that stops at "metal conducts better" describes but does not explain, and caps at 2.

5. State the principle of conservation of energy (1 mark)

Energy cannot be created or destroyed, only transferred from one store to another; the total energy of a closed system remains constant.

Common mistake: "energy is used up". Energy is transferred or dissipated, never used up — this wording is treated as a physics error.

6. A 500 W heater is used for 4.0 minutes. Calculate the energy transferred (3 marks)

Convert time to seconds:   4.0 × 60 = 240 s

E = P × t
  = 500 × 240
  = 120 000 J
  = 1.2 × 10⁵ J   (or 120 kJ)

Where the marks sit: 1 for converting minutes to seconds, 1 for the equation, 1 for the answer with units.

This is the trap: forgetting the conversion gives 2000 J, an answer 60× too small. Cambridge deliberately quotes times in minutes for this reason.

7. Describe what happens to the particles of a solid as it is heated until it melts (4 marks)

1. The particles gain kinetic energy and vibrate more vigorously about fixed positions
2. The temperature rises while this happens
3. At the melting point, further energy breaks the forces of attraction between particles rather than increasing their speed
4. Temperature stays constant during melting while the particles become free to move past one another

Where the marks sit: 1 per stage. The fourth is the discriminating mark — most answers omit that temperature is constant during a change of state.

8. A wave has a frequency of $250\ \text{Hz}$ and travels at $340\ \text{m/s}$. Calculate its wavelength (2 marks)

v = f λ

        v      340
λ  =  ----- = ------  =  1.36 m
        f      250

Where the marks sit: 1 for rearranging correctly, 1 for the answer with units.

9. State the law of reflection (2 marks)

The angle of incidence equals the angle of reflection, both measured from the normal.

Where the marks sit: 1 for equal angles, 1 for measured from the normal. The second half is frequently missing and is half the mark.

10. Two resistors, $4\ \Omega$ and $6\ \Omega$, are connected in series across a $12\ \text{V}$ supply. Calculate the current (3 marks)

Series: R_total = 4 + 6 = 10 Ω

        V      12
I  =  ----- = -----  =  1.2 A
        R      10

Where the marks sit: 1 for total resistance, 1 for applying $V = IR$, 1 for the answer with units.

Sense check: in series the total resistance is always larger than any single resistor, and the current is the same through both. If you calculated different currents, you used the parallel rules.

Cambridge command words, and what each one buys you

The single highest-yield habit in IGCSE Physics is reading the command word first and shaping the answer to it. A perfect description scores roughly half marks on an explain question, and writing more does not fix it.

Where to go next

• KCSE Physics Practice Paper 1 — the same physics, different question style
• GCSE Mathematics Practice Paper 1 — the rearrangement practice these calculations rely on

Ask StudyAI to generate questions using a specific command word, so you can drill the shape of the answer rather than only the content.