3.4 Specific heat capacity
9 exam questions worth 23 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Calculate the energy needed to raise the temperature of 0.50 kg of water by 30 °C. The specific heat capacity of water is 4200 J/kg °C.
Mark scheme
ΔE = m c Δθ (1); 0.50 × 4200 × 30 (1); 63 000 J (1)
Model answer
ΔE = m c Δθ = 0.50 × 4200 × 30 = 63 000 J.
A 2.0 kg block of metal is supplied with 18 000 J of energy. Its temperature rises from 20 °C to 30 °C. Calculate the specific heat capacity of the metal.
Mark scheme
Δθ = 10 °C and c = ΔE / (m Δθ) (1); 18 000 / (2.0 × 10) (1); 900 J/kg °C (1)
Model answer
Δθ = 30 − 20 = 10 °C. c = ΔE / (m Δθ) = 18 000 / (2.0 × 10) = 900 J/kg °C.
840 000 J of energy is supplied to 10 kg of water. Calculate the temperature rise. The specific heat capacity of water is 4200 J/kg °C.
Mark scheme
Δθ = ΔE / (m c) (1); 840 000 / (10 × 4200) (1); 20 °C (1)
Model answer
Δθ = ΔE / (m c) = 840 000 / (10 × 4200) = 20 °C.
Define the term specific heat capacity.
Mark scheme
the energy needed to raise the temperature (1); of 1 kg of a substance by 1 °C (1)
Model answer
The energy needed to raise the temperature of 1 kg of a substance by 1 °C.
Explain why water is used in central heating systems.
Mark scheme
water has a high specific heat capacity (1); so a given mass of water stores / carries a large amount of energy (1); and releases it as it cools in the radiators (1)
Model answer
Water has a high specific heat capacity, so each kilogram can carry a large amount of energy from the boiler. It then releases this energy as it cools in the radiators.
Four blocks of equal mass are each supplied with the same amount of energy. Which block has the greatest temperature rise?
Choose one answer.
Correct Not quite: the answer is Copper (390 J/kg °C)
Mark scheme
D: copper (lowest specific heat capacity)
Model answer
Copper (D), because it has the lowest specific heat capacity, so the same energy gives the biggest temperature rise.
A 2.0 kg block of aluminium at 20 °C is supplied with 90 000 J of energy. The specific heat capacity of aluminium is 900 J/kg °C. Calculate the final temperature of the block.
Mark scheme
Δθ = ΔE ÷ (m c) = 90 000 ÷ (2.0 × 900) (1); 50 °C (1); final temperature = 20 + 50 = 70 °C (1)
Model answer
Δθ = 90 000 / (2.0 × 900) = 50 °C. The final temperature is 20 + 50 = 70 °C.
A kettle contains 1.5 kg of water at 20 °C. Calculate the energy needed to heat the water to 100 °C. (c = 4200 J/kg °C)
Mark scheme
Δθ = 80 °C (1); ΔE = m c Δθ = 1.5 × 4200 × 80 (1); 504 000 J (1)
Model answer
Δθ = 100 − 20 = 80 °C. ΔE = 1.5 × 4200 × 80 = 504 000 J.
Explain why places near the sea usually have a smaller range of temperatures through the year than places far from the sea.
Mark scheme
water has a high specific heat capacity, so it warms and cools slowly (1); so the sea keeps the temperature of the nearby land / air more constant (1)
Model answer
Water has a high specific heat capacity, so the sea heats up and cools down slowly. This keeps the air and land near it milder in both summer and winter.
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