### What is Specific Heat Capacity?

**The specific heat capacity of a substance in the amount of thermal energy required to raise the temperature of 1kg of that substance by 1 °C**- Specific heat capacity has units of
**joules per kilogram per degree Celsius (J/kg °C)**(

**Note:**Different substances have different specific heat capacities)

- From the definition of specific heat capacity, it follows that if you have more than 1 kg of a material, you will need more thermal energy

Likewise, if you want to raise its temperature by more than 1 °C, you will also need to add more thermal energy - The amount of thermal energy needed is given by the equation:

- Note that in the above equation:
is used to mean the change in internal energy*ΔE*is used to mean the specific heat capacity of the substance*C*is used to mean the change in temperature*ΔT*

(The symbol Δ in maths is used to denote a change in value)

**High v low specific heat capacity**

### Measuring Specific Heat Capacity

- In your IGCSE examination you may be asked to describe an experiment to determine the specific heat capacity of a substance

A method for carrying out such an experiment is given below

- In this experiment you need to use the following equation to determine the specific heat capacity of the substance:

- The following apparatus will be needed:
- A block of the substance (preferably 1kg in mass) or in the case of a fluid, a beaker containing a known mass of the fluid
- A thermometer
- An appropriate heater (e.g. an immersion heater)
- A power source
- A joule meter or a voltmeter, ammeter and stop-clock (I will assume we have the latter)

*Apparatus to determine the specific heat capacity of a 1 kg Aluminium block*

* *

- Start by assembling the apparatus and measure the initial temperature of the substance
- Turn on the power supply and start the stop-clock
- Whilst the power supply is on take several periodic measurements of the voltage and current, and calculate an average of these values
- After 5 minutes (300 seconds) switch off the power supply, stop the stop-clock and leave the apparatus for a few more minutes
- Monitor the thermometer and make a note of the highest temperature reached
- Calculate the rise in temperature
- The heat supplied to the substance can be calculated using the equation:

energy = current × voltage × time

(Note: the time must be in seconds)

- These values, along with the mass of the substance, can now be substituted into the top equation to find the specific heat capacity of the substance
- The biggest problem with the above experiment is that not all of the heat supplied by the heater will go into the substance – some will go into the surroundings and the substance will also lose heat whilst it is being heated
- This means that the value for the heat added will be too great which means that the calculated specific heat capacity will also be too great