Required practical

Determining the specific heat capacity of a metal

There are different ways to investigate methods of insulation. In this required practical activity, it is important to:

  • make and record potential difference, 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

Aim of the experiment

To measure the specific heat capacity of a sample of material.

Method

  1. Place the immersion heater into the central hole at the top of the block.
  2. 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.
  3. Fully insulate the block by wrapping it loosely with cotton wool.
  4. Record the temperature of the block.
  5. Connect the heater to the power supply and turn it on for ten minutes taking note of the ammeter and voltmeter readings.
  6. 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.
An illustration correctly showing the set up of a specific heat capacity practical

Results

Record results in a suitable table. The example below shows some suitable results.

Ammeter reading (A)Voltmeter reading (V)Initial temperature (°C)Final temperature (°C)
3.6510.801538

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 × current × time

\text{E} = \text{V} \times \text{I} \times \text{t}

= 10.80 × 3.65 × 600

\text{E} = 23,700 J

\text{E} = \text{mc}\Delta \text{T}

\text{c} = \frac{\text{E}}{\text{m}\Delta \text{T}}

\frac{23,700}{1 \times (38 - 15)}

\frac{23,700}{1 \times (23)}

\text{c} = 1,030 J/kg°C

The actual value for the specific heat capacity of aluminium is 900 J/kg°C. The calculated value does not match exactly but it is close to the true value.

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, the thermometer and the heater itself. This causes the calculated specific heat capacity to be higher than for one kilogram (kg) of aluminium alone.

Hazards and control measures

HazardConsequenceControl measures
Hot immersion heater and sample materialBurn skinDo 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.
Move on to Video
next