Specific heat capacity

An investigation to determine the specific heat capacity of one or more materials.

Students must investigate the specific heat capacity of various materials. The practical links work done to an increase in temperature. Students are assessed on their safe use of appropriate equipment. The investigation involves the measuring of mass and temperature change of a block calorimeter which is heated using an immersion heater. Students will also calculate work done by the heater and plot their results on a graph.

Equipment (per participant)

• Safety glasses
• Calorimeter and blocks (in
various materials)
• Insulating jackets for the
calorimeter blocks
• Thermometer
• 3ml pipette
• Immersion heater

• Bench power supply
• Connecting leads
• Ammeter
• Voltmeter
• Electronic balance (2dp)
• Stopwatch
• Heatproof mat

Method

Using an electronic balance, students must weigh one of the block calorimeters and note the value in kilograms and the material of the block in a suitable table which shows weight, temperature and time.
Students should place the block calorimeter in an Insulating Jacket.
The immersion heater is inserted into the large hole on the block calorimeter.
The immersion heater, ammeter and power supply are connected in series.
The students then connect the voltmeter across the immersion heater.
Using a pipette, a drop or two of water is added into the smallest hole in the block calorimeter and the thermometer is inserted. The drops of water ensure better thermal contact with the thermometer.
Students should ensure that the power supply is set to 12V and switch it on to give power to the heater.
The readings on the voltmeter and ammeter are recorded in their table. These should stay the same throughout the experiment.
The starting temperature on the thermometer is noted and the stopclock is started. Students must record the temperature every 60 seconds for 10 minutes.
After the ten minutes is up, students switch off the power supply, taking care not to touch or move the calorimeter block as it will be hot.
The procedure is then repeated using calorimeter blocks of differing materials.
Students then calculate the power of the heater they have used in watts. To do this, they must multiply the readings on the ammeter and voltmeter together.
For each temperature measurement taken, the energy transfer/work done by the heater is calculated by multiplying the time in seconds by the power of the heater and these values are added to their table.
Students now plot their values on a graph showing temperature against work done and draw a line of best fit on their graph, being cautious due to the beginning of the graph being curved.
They can now calculate the gradient of this line of best fit by dividing the change in temperature rise by the change in work done.
The specific heat capacity of a block is calculated using the formula: one divided by the gradient value, which equates to the amount of heat energy (Joules) needed to increase the temperature of the block by 1°C.
Calculate the specific heat capacity of each block using the following equation:

Change in thermal energy (J) = mass in kg x specific heat capacity in J/kg/°C x temperature change

Technician tips

Power to the circuit must be switched off whilst drops of water are added to the thermometer hole.
Calorimeter blocks could be distributed as a circus.
Care should be taken that the calorimeter blocks and immersion heaters are cool before students begin dismantling their equipment.