4️⃣ PAG5: Investigate ‘work done’ and measure the specific heat capacity of a metal.

Question 1

Health and safety

Answer 1

The heater and metal block will get hot, learners should be warned not to touch hot objects and a heatproof mat should be used to protect working surfaces.
Electric circuits should be checked to ensure that they are connected correctly.

Question 2

Equipment

Answer 2

• Metal block (with provision to accommodate electric heater and thermometer)
• Low voltage electric heater
• Low voltage power supply
• Voltmeter
• Ammeter
• Stopclock
• Thermometer
• Connecting leads
• Heatproof mat
• Insulating materials (for extension)
Alternative equipment
CENTRE SHOULD AMEND WORKSHEET BASED ON EQUIPMENT PROVIDED
• Joulemeter ( in place of voltmeter and ammeter)
• Data logger with voltage, current and temperature sensors (in place of voltmeter, ammeter, stopclock and thermometer)

Question 3

Method

Answer 3

1. Connect the circuit as shown in the diagram below and ask your teacher to check it. Make sure that the metal block and heater are placed on the heatproof mat. -

Place an electrical immersion heater into the central hole at the top of the weighed metal block.
Connect the heat in series with an ammeter and in parallel with a voltmeter.
Place the thermometer into the smaller hole. Add two drops of oil into the hole to make sure the thermometer is surrounded by hot material.
Insulate the block by wrapping it with cotton wool.

2. Record the mass of the metal block.
3. Record the temperature of the metal block before turning on the power supply.
4. Turn on the power supply with the voltage set at the value instructed by your teacher.
5. Leave the block to heat for 20 minutes or other time given by your teacher. Check that the voltage remains constant during this time.
6. Record the current at the start of the heating
7. Calculate the power of the heater from the voltage and current.
8. Calculate the energy transferred from the power and time.
9. Record the temperature at the end of the heating time.
10. Calculate the energy transferred for each degree centigrade
11. Calculate the energy which would be required to raise the temperature of 1kg of the metal by one degree centigrade.

Question 4

The value obtained from the experiment is much higher than expected.
Give two reasons how this could have occurred and write down two improvements to the experimental procedure. [4 marks

Answer 4

Reasons
Heat escapes to the surroundings 
Part of the immersion heater is outside the block 
Poor thermal conduct between the immersion heater and block 
It takes time for the thermometer to reach its maximum temperature (once the heater is turned off) 

Improvements
Lag/insulate the metal block 
Make sure all the heater is in the block 
Use petroleum jelly to transfer heat between the immersion heater and the block 
Wait until the max temperature is reached 

Question 5

Hazards and control measures

Answer 5

Hot immersion heater and sample material Burnt skin Do not touch the heater when switched on. Position it away from the edge of the bench. Allow time to cool before packing away equipment. Run any burn under cold running water for at least 10 minutes.