IGCSE · 2 · practical
Thermal physics · Question 10
Thermal physics · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- demanding
- Marks
- 8
- Topics
- 1
- Answer
- Complete
A student determines the specific heat capacity of aluminium. She uses a 1.0 kg aluminium block with two narrow holes drilled in it, one holding a 48 W electric immersion heater and the other a thermometer. She switches on the heater and records the temperature every 2 minutes.
| time / minutes | 0 | 2 | 4 | 6 | 8 |
|---|---|---|---|---|---|
| temperature / °C | 19.0 | 24.5 | 30.0 | 35.5 | 41.0 |
- (a)
Determine Determine the temperature rise over the 8 minutes, and hence determine a value for the specific heat capacity of aluminium.
4 marks - (b)
Suggest The accepted value for the specific heat capacity of aluminium is 900 J/(kg °C). Suggest why the student's value is higher than this.
2 marks - (c)
Suggest Suggest two improvements to the student's method that would give a more accurate value.
2 marks
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(a)
Determine Determine the temperature rise over the 8 minutes, and hence determine a value for the specific heat capacity of aluminium.
Turn the task into a measurable method: name the independent, dependent and controlled quantities; describe apparatus and repeats; then explain how the evidence will be processed and how uncertainty or safety will be managed.
- 1
Δθ = 41.0 − 19.0 = 22.0 °C
- 2
energy supplied E = Pt = 48 × 480 = 23 040 J
- 3
c = E / (mΔθ) = 23 040 / (1.0 × 22.0)
- 4
c = 1050 J/(kg °C) (accept 1000–1100)
(b)
Suggest The accepted value for the specific heat capacity of aluminium is 900 J/(kg °C). Suggest why the student's value is higher than this.
Turn the task into a measurable method: name the independent, dependent and controlled quantities; describe apparatus and repeats; then explain how the evidence will be processed and how uncertainty or safety will be managed.
- 1
thermal energy is transferred from the block to the surroundings, so not all of the 23 040 J raises the temperature of the block
- 2
the measured Δθ is therefore smaller than it should be for that energy, making the calculated c too large
(c)
Suggest Suggest two improvements to the student's method that would give a more accurate value.
Turn the task into a measurable method: name the independent, dependent and controlled quantities; describe apparatus and repeats; then explain how the evidence will be processed and how uncertainty or safety will be managed.
- 1
lag the block with insulation / place it in an insulated container
- 2
any one of: put oil in the holes to improve thermal contact; start below and finish above room temperature; take readings more frequently and plot a graph; use a datalogger
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