A2 Daily A Level Physics question

2026-04-10 OCR A Thermal physics I (M5.1) Module 5.1.1 Internal energy and temperature (qualitative) Module 5.1.2 Specific heat capacity

Two identical 200 W immersion heaters are placed in identical insulated beakers, each containing 0.50 kg of liquid at the same initial temperature. One beaker holds water and the other holds cooking oil. Assume no heat losses and no phase change. After 3.0 minutes of heating, which statement must be true?

A The water’s temperature rise is greater because a higher specific heat capacity means it heats up faster.
B The oil’s temperature rise is greater because less energy is needed per degree of warming. (correct)
C Their temperatures are the same because each received the same energy for the same time.
D Both gain the same increase in internal energy, so the liquid with the higher specific heat capacity ends up at the higher temperature.

Answer

The correct answer is B.

Correct: B — The oil’s temperature rise is greater because less energy is needed per degree of warming. A Higher specific heat capacity means more energy is required per degree, so water would warm more slowly, not faster. B This is the only correct reasoning: for the same energy input to the same mass, a lower specific heat capacity gives a larger temperature rise. C Equal energy input does not imply equal temperature change when the specific heat capacities differ. D Although both gain the same increase in internal energy (same power × time), the higher specific heat capacity actually gives a smaller temperature rise, so it need not be hotter.

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