This set mixes the five skills from thermal processes: expansion, the three transfer processes, temperature-time graphs, temperature against thermal energy and insulation. All questions and data are original and invented for practice. They are not from any past paper.
Work each question on paper first, write units in every answer and write full sentences for explanations. Then open the worked answer.
Keep a note of the ones you miss, and the mistake log and retest queue can help you sort them by error type. The bounds and rounding explainer is useful when you decide how many digits to quote.
Questions, easy to harder
Q1. Name the process by which energy travels from the Sun to Earth, and say why it can cross space.
Show answer
Radiation. It is carried by electromagnetic waves, which need no particles, so they can travel through the vacuum of space.
Q2. A metal rod is heated. Complete the sentence: the particles vibrate ______ and the average spacing ______.
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The particles vibrate more strongly and the average spacing increases. The particles themselves do not get bigger.
Q3. Put these in order from the most expansion to the least for the same temperature rise: iron bar, air, water.
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Air, water, iron. Gases expand most because their particles are far apart with weak forces. Liquids expand less and solids least.
Q4. Which process is mainly responsible for each? (a) A metal spoon in hot tea warms up. (b) Warm air rises above a stove. (c) You feel warm near a bonfire without touching it.
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(a) Conduction. (b) Convection. (c) Radiation.
Q5. A liquid is heated at steady power. Invented readings: 25 °C at 0 min, 65 °C at 4 min, 65 °C from 4 to 10 min, then 85 °C at 12 min. Find the melting or boiling point, the length of the flat section and the initial rate of rise.
Show answer
The flat section is at 65 °C. It lasts 10 − 4 = 6 min. Initial rate = (65 − 25) ÷ 4 = 40 ÷ 4 = 10 °C/min. The flat section means a change of state, with energy going in to break bonds.
Q6. A student says “the graph is flat between 4 and 10 min, so the heater is off.” Correct the statement.
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The heater is still supplying energy. The energy is used to overcome the forces between particles during a change of state, so the temperature stays constant.
Q7. Why is a sea breeze felt on a Malaysian beach during the day? Use convection in your answer.
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During the day the land warms faster than the sea. Air above the land is warmed, expands, becomes less dense and rises. Cooler, denser air from above the sea moves in to replace it, which is felt as a breeze from the sea.
Q8. Two samples of water: 2 kg at 40 °C and 0.5 kg at 70 °C. Which has the higher temperature, and which holds more thermal energy above 0 °C? Use 4200 J/(kg °C).
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The 0.5 kg sample has the higher temperature, 70 °C. Energy for the 2 kg sample: 2 × 4200 × 40 = 8400 × 40 = 336 000 J. Energy for the 0.5 kg sample: 0.5 × 4200 × 70 = 2100 × 70 = 147 000 J. The 2 kg sample holds more, although it is cooler.
Q9. A 250 W heater melts a solid for exactly 6 minutes at constant temperature. Find the energy supplied, assuming all of it reaches the solid. If the sample has a mass of 0.3 kg, find the energy per kg.
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Time = 6 × 60 = 360 s. Energy = 250 × 360 = 90 000 J. Energy per kg = 90 000 ÷ 0.3 = 300 000 J/kg. This quantity is explored in heat calculations.
Q10. Two identical cans of water start at 90 °C. One is painted matt black and one is polished silver. Which cools faster, and why?
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The matt black can cools faster. Dark matt surfaces are good emitters of infrared radiation, while polished silver is a poor emitter and reflects radiation. The difference is in radiation, because the water, cans and surroundings are the same otherwise.
Q11. A flask keeps tea hot. After 20 min, flask P has cooled from 85 °C to 73 °C. Flask Q has cooled from 85 °C to 67 °C. Find each cooling rate and say which is better insulated. Then name two features that make a good flask.
Show answer
P: (85 − 73) ÷ 20 = 12 ÷ 20 = 0.6 °C/min. Q: (85 − 67) ÷ 20 = 18 ÷ 20 = 0.9 °C/min. P is better insulated because it loses energy more slowly. Two features: a vacuum between double walls (no conduction or convection) and silvered surfaces (reduce radiation). A stopper reduces convection and evaporation.
If you got these wrong
| Error you made | Questions | Go to |
|---|---|---|
| Said particles expand, or wrong order of expansion | Q2, Q3 | explain expansion using a particle model |
| Named the wrong transfer process, or “heat rises” | Q1, Q4, Q7 | compare conduction, convection and radiation |
| Misread a flat section or a gradient | Q5, Q6, Q9 | interpret a temperature-time graph |
| Mixed up temperature and thermal energy | Q8 | distinguish temperature from thermal energy |
| Wrong insulation reasoning or cooling rate | Q10, Q11 | explain insulation from a supplied structure |
What to do next
If you scored well across all five groups, move on to heat calculations or browse the Physics learning guide. If one group keeps slipping, repeat that lesson and retry the question with different numbers.
Some students can do these in a quiet hour but not mixed into a timed paper. That is worth raising in online one-to-one Physics tuition, where a teacher can see where your reasoning goes wrong as you write.