# 2.2.5 Specific Heat Capacity

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### 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:
• ΔE is used to mean the change in internal energy
• C is used to mean the specific heat capacity of the substance
• ΔT is used to mean the change in temperature

(The symbol Δ in maths is used to denote a change in value) High v low specific heat capacity

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### 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 ### Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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