Required practical - measuring specific heat capacity
There are different ways to investigate methods of insulation. In this practical activity, it is important to:
- make and record potential differenceThe potential difference (or voltage) of a supply is a measure of the energy given to the charge carriers in a circuit. Units = volts (V). This is the voltage between two points that makes an electric current flow between them., current and time accurately
- measure and observe the change in temperature and energy transferred
- use appropriate apparatus and methods to measure the specific heat capacity of a sample of material
Learn about the specific heat capacity practical in this podcast.
Listen to the full series on 大象传媒 Sounds.
Aim of the experiment
To measure the specific heat capacity of a sample of material.
Method
- Place the immersion heater into the central hole at the top of the block.
- Place the thermometer into the smaller hole and put a couple of drops of oil into the hole to make sure the thermometer is surrounded by hot material.
- Fully insulate the block by wrapping it loosely with cotton wool.
- Record the temperature of the block.
- Connect the heater to the power supply and turn it off after ten minutes.
- After ten minutes the temperature will still rise even though the heater has been turned off and then it will begin to cool. Record the highest temperature that it reaches and calculate the temperature rise during the experiment.
Record results in a suitable table. The example below shows some sample results.
| Ammeter reading (A) | Voltmeter reading (V) | Initial temperature (掳C) | Final temperature (掳C) |
| 3.65 | 10.80 | 15 | 38 |
| Ammeter reading (A) | 3.65 |
|---|---|
| Voltmeter reading (V) | 10.80 |
| Initial temperature (掳C) | 15 |
| Final temperature (掳C) | 38 |
Analysis
The block has a mass of 1 kg and the heater was running for 10 minutes = 600 seconds.
Using the example results:
energy transferred = potential difference 脳 current 脳 time
\(E = V \times I \times t\)
\(E = 10.90 \times 3.65 \times 600\)
\(E = 23,700~J\)
\(E = mc \Delta T\)
\(c = \frac{E}{m \Delta T}\)
\(c = \frac{23,700}{1 \times (23)}\)
\(c = 1,030 J/kg掳C\)
The actual value for the specific heat capacity of aluminium is 900 J/kg掳C. The calculated value does not match exactly but it is in the correct order of magnitude.
Evaluation
- All experiments are subject to some amount of experimental error due to inaccurate measurement, or variables that cannot be controlled. In this case, not all of the heat from the immersion heater will be heating up the aluminium block, some will be lost to the surroundings.
- More energy has been transferred than is needed for the block alone as some is transferred to the surroundings. This causes the calculated specific heat capacity to be higher than for 1 kg of aluminium alone.
Evaluation
| Hazard | Consequence | Control measures |
| Hot immersion heater and sample material | Burnt skin | Do not touch when switched on. Position away from the edge of the desk. Allow time to cool before packing away equipment. Run any burn under cold running water for at least 10 minutes. |
| Hazard | Hot immersion heater and sample material |
|---|---|
| Consequence | Burnt skin |
| Control measures | Do not touch when switched on. Position away from the edge of the desk. Allow time to cool before packing away equipment. Run any burn under cold running water for at least 10 minutes. |