Specific heat capacity practical
Use electrical heating measurements to calculate specific heat capacity and evaluate energy losses.
Practise the calculations · Print a classroom set
Apparatus and measurements
A low-voltage heater and temperature probe fit into holes in a metal block. Measure the block’s mass, insulate it, and measure electrical energy input with a joulemeter or with potential difference, current and time.
Larger apparatus diagram
Method and controls
- Measure the block’s mass. Place the heater and probe in good thermal contact with the block. Record the initial temperature after it has settled.
- Switch on the low-voltage supply and record energy input and temperature at regular intervals. If using E = VIt, monitor current and potential difference; that shortcut assumes they remain constant.
- Use the increase in temperature, not the final temperature. A graph of energy input on the vertical axis against temperature rise on the horizontal axis has gradient mc in the ideal model. Divide this gradient by mass to estimate c.
Results to analyse
Original synthetic data for practice.
| Elapsed time / s | Temperature / °C |
|---|---|
| 0 | 20.0 |
| 120 | 24.0 |
| 240 | 28.0 |
| 360 | 32.0 |
Questions
- For this idealised dataset, the block mass is 0.500 kg and heater power is 15.0 W. Find energy input after 360 s.
- Calculate the specific heat capacity assuming all input heats the block.
- In a real experiment some input heats the surroundings. If this is ignored, is the calculated c too high or too low? Explain.
Show worked answers
- E = Pt = 15.0 × 360 = 5400 J.
- Temperature rise = 32.0 − 20.0 = 12.0 °C. c = 5400/(0.500 × 12.0) = 900 J kg⁻¹ °C⁻¹.
- It is too high under the stated model: input energy exceeds energy gained by the block, while the measured rise reflects the smaller energy gain. Heater and probe heat capacity can also affect the result.
Evaluation
Insulation reduces heat transfer to the surroundings. Good thermal contact helps the probe track block temperature; waiting alone does not remove heat loss. Temperature lag and a changing rate of loss can spoil an assumed straight line.
The block and heater can become hot. Use a school-approved low-voltage setup and allow it to cool before handling. These data are synthetic, not experimental evidence for a particular metal.
Specification links
AQA 8463: Required practical 1; 4.1.1.3. OCR Gateway J249: P1.2d–e; PAG P5 (selected). Selected skills only; no practical-completion assessment.
Continue with calculation practice · Graph skills · All six practical guides