Specific Heat Capacity (Oxford AQA IGCSE Combined Science Double Award)
Revision Note
Specific Heat Capacity
If the temperature of a system increases, this depends on:
The mass of the substance heated
The type of material
The energy input to the system
The specific heat capacity, of a substance is defined as:
The amount of energy required to change the temperature of one kilogram of the substance by one degree Celsius.
Different substances have different specific heat capacities
If a substance has a low specific heat capacity, it heats up and cools down quickly
It takes less energy to change its temperature
If a substance has a high specific heat capacity, it heats up and cools down slowly
It takes more energy to change its temperature
Specific heat capacity examples
Energy is transferred to the thermal store of a substance
The amount of energy needed to raise the temperature of a given mass by a given amount can be calculated using the equation:
Where:
ΔE = change in energy, in joules (J)
m = mass, in kilograms (kg)
c = specific heat capacity, in joules per kilogram per degree Celsius (J / kg °C)
Δθ = change in temperature, in degrees Celsius (°C)
Uses of specific heat capacity
Specific heat capacity is mainly used for liquids and solids
The specific heat capacity of different substances determines how useful they would be for a specific purpose e.g. choosing the best material for kitchen appliances
Good electrical conductors, such as copper and lead, are excellent conductors of heat due to their low specific heat capacity
On the other hand, water's high specific heat capacity makes it ideal for heating homes as the water remains hot in a radiator for a long time
Examiner Tip
This equation will be given on your equation sheet, so don't worry if you cannot remember it, but you must understand how to use it. In a question, you will always be given the specific heat capacity of a substance, so you do not need to memorise any values.
Worked Example
Water of mass 0.48 kg is increased in temperature by 0.7 °C. The specific heat capacity of water is 4200 J / kg °C.
Calculate the amount of energy transferred to the water.
Answer:
Step 1: Write down the known quantities
Mass, m = 0.48 kg
Change in temperature, Δθ = 0.7 °C
Specific heat capacity, c = 4200 J / kg °C
Step 2: Write down the relevant equation
Step 3: Calculate the energy transferred by substituting in the values
Step 4: Round the answer to 2 significant figures
Determining specific heat capacity
The specific heat capacity of a substance can be determined experimentally
The equipment below can be used to heat an aluminium block with a known mass,
Equipment used for finding the specific heat capacity of an aluminium block
The joulemeter can be used to measure the amount of energy transferred to the block, , during heating
The temperature before and after heating can be measured to determine the temperature change,
The specific heat capacity, , of the aluminium block can then be calculated using the equation:
Examiner Tip
An alternative method to calculate the energy transferred to the heater would be using an ammeter to measure the current, a voltmeter to measure the voltage, and a stopwatch to measure the time the block was heated. Then use to determine the power and to determine the energy transferred, .
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