Change of State
6 marks · NormalA student carries out an experiment to find the specific heat capacity of water. The following results are obtained:
| Mass of water (kg) | Initial temp (°C) | Final temp (°C) | Current (A) | Voltage (V) | Time (s) |
|---|---|---|---|---|---|
| 0.80 | 20 | 60 | 2.0 | 12 | 300 |
Calculate the total energy supplied by the heater (in J).
Use the data to calculate the specific heat capacity of water based on this experiment.
Suggest one reason why the value found might be higher than the actual specific heat capacity of water.
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.
Show answer
(a) 7200 J
(b) 225 J/kg °C
(c) Some energy is lost to the surroundings · must show Heat loss to surroundings
Common mistakes: Wrong calculation of ΔT; Omitting to multiply voltage and current
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Calculates power: P = VI
A1 (a) · 1 mark · Calculates energy: E = P × t, includes correct units. (follow-through)
M2 (b) · 1 mark · Uses c = ΔQ / (m × ΔT) with energy from part (a) (follow-through)
A2 (b) · 1 mark · Correctly substitutes all values in calculation. (follow-through)
A3 (b) · 1 mark · Arrives at final value for c with suitable unit.
B1 (c) · 1 mark · Gives a sensible experimental reason (e.g. energy loss).
Worked solution
(a) Calculate energy supplied:
(b) Calculate c:
(c) The value might be high because some energy was lost to the surroundings or used to heat the apparatus.