RP1: Specific Heat Capacity

Question 1

What is the aim of this experiment?

Answer 1

• To determine the specific heat capacity of one or more materials, correlating a decrease of
  one energy store (work done) to the increase in temperature and increase in thermal energy
  stored in another

Question 2

Describe how we can determine the specific heat capacity of one or more materials (method)

Answer 2

1) Measure and record mass of copper block in kg
2) Place heater in large hole in block. connect ammeter, power pack and heater in series
3) Connect voltmeter across the power pack
4) Put small amount of water in other hole using pipette
5) Put thermometer in this hole
6) Switch the power pack to 12V and switch it on
7) Record the ammeter and voltmeter readings; these shouldn’t change during experiment
8) Measure temperature and switch on stop clock
9) Record temperature every minute for 10 minutes
10) Calculate power of the heater in watts. to do this, multiply ammeter reading by voltmeter reading
11) Calculate work done by heater. to do this, multiply the time in seconds by the power of the heater

Question 3

Describe how you can show your results

Answer 3

1) Plot a graph of temperature in ºC against work done in J
2) Draw a line of best fit (the start of the graph may be curved)
3) Calculate the gradient of the straight part of your graph
4) The heat capacity of the block is 1/gradient
5) The specific heat capacity is the heat capacity divided by the mass of the block in kg

Question 4

How can you develop this investigation?

Answer 4

• Repeat the experiment for other blocks e.g. aluminium and iron.
• If metal blocks have the same mass, the bigger the volume, the bigger the specific heat capacity

Question 5

List some safety precautions

Answer 5

• Take care handling hot water, be careful not to scold yourself and mop up any water
  spillages.
• Avoid spilling water on any electrics of the infrared detector

Question 6

If the power of the heater being used isn’t given, how can you calculate it?

Answer 6

• By connecting it in parallel with a voltmeter and in series with an ammeter
• Then apply the equation P=IV

Question 7

Why do the metal blocks used in the experiment have two holes in them?

Answer 7

• One is for the heater, the other for the thermometer

Question 8

What can be done to improve the reading given by the thermometer?

Answer 8

• Add a few drops of water in the hole with the thermometer to improve the thermal contact and ensure even heating

Question 9

What reading do you record and how frequently?

Answer 9

• Record the temp value every 10 minutes

Question 10

What graph do you plot with the data?

Answer 10

• Temp against work done by the heater

Question 11

How do you calculate work done by the heater?

Answer 11

• Energy = Power of the heater x Time

Question 12

Once the block has initially warmed up, describe the relationship between the temp and work done by heater

Answer 12

• Linear relationship - straight line

Question 13

If you start timing from when you switch on the heater, why may the graph not initially be linear?

Answer 13

• There will initially be some thermal inertia whilst the block and heater warm up

Question 14

What does the gradient of the graph represent?

Answer 14

• The inverse of the heat capacity for the metal block

Question 15

How do you obtain the specific heat capacity for the metal you are measuring?

Answer 15

• Divide the inverse of the gradient by the mass of the metal block used

Question 16

Why should you wrap insulation around the outside of the metal block?

Answer 16

• To reduce the heat loss to the environment and ensure the temp reading is as accurate as possible