Practical: investigate the specific heat capacity of a substance
4 marks · NormalA student is investigating the specific heat capacity of a 0.40 kg block of lead. The block is heated using an immersion heater connected to a power supply as shown. The voltage across the heater is 15 V and the current is 2.0 A. The heater is switched on for 300 seconds.
Calculate the total thermal energy supplied to the block by the heater.
The temperature of the block increases by 25 °C during the experiment. Calculate the specific heat capacity of lead. Give your answer in J/kg °C.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) 9000 J
(b) 900 J/kg °C
Common mistakes: Incorrect substitution; Confusion of units (mass in g not kg)
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correct use of Q = V × I × t.
A1 (a) · 1 mark · Correct answer for energy (9,000 J) with appropriate substitution and units.
M2 (b) · 1 mark · Correct rearrangement of c = Q/(m×Δθ) and substitution. (follow-through)
A2 (b) · 1 mark · Correct answer for c (900 J/kg °C) to two significant figures, with correct units. (follow-through)
Worked solution
a) The energy supplied to the heater is calculated using Q = V × I × t.
b) The specific heat capacity is given by c = Q / (m × Δθ).