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Specific Heat Capacity (Oxford AQA IGCSE Physics)

Revision Note

Ann Howell
Oxford AQA PhysicsOxford AQA Combined Science Double Award: Physics

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, c 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

A copper block has a specific heat capacity of 390 J per kg per degree Celsius. An aluminium block has a specific heat capacity of 910 J per kg degree's Celcius. Water has a specific heat capacity of 4200 J per kg per degree Celsius, for IGCSE & GCSE Physics revision notes
The specific heat capacity of water is higher than copper and aluminium because it takes more energy to change the temperature of water

  • 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:

increment E space equals space m cross times c cross times increment theta

  • 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 

increment E space equals space m space cross times space c space cross times space increment theta

Step 3: Calculate the energy transferred by substituting in the values

increment E space equals space 0.48 space cross times space 4200 space cross times space 0.7 space equals space 1411.2

Step 4: Round the answer to 2 significant figures

increment E space equals space 1400 space straight J

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, m

Equipment used for finding the specific heat capacity of an aluminium block

An immersion heater and thermometer are inserted into an aluminium block. The immersion heater is connected in series to a power supply and a joulemeter
Apparatus to investigate the specific heat capacity of the aluminium block

  • The joulemeter can be used to measure the amount of energy transferred to the block, straight capital delta E, during heating

  • The temperature before and after heating can be measured to determine the temperature change, capital delta theta

  • The specific heat capacity, c, of the aluminium block can then be calculated using the equation:

c space equals space fraction numerator straight capital delta E over denominator m cross times straight capital delta theta end fraction

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 P space equals space V cross times I to determine the power and E space equals space P cross times t to determine the energy transferred, straight capital delta E.

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    Ann Howell

    Author: Ann Howell

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    Ann obtained her Maths and Physics degree from the University of Bath before completing her PGCE in Science and Maths teaching. She spent ten years teaching Maths and Physics to wonderful students from all around the world whilst living in China, Ethiopia and Nepal. Now based in beautiful Devon she is thrilled to be creating awesome Physics resources to make Physics more accessible and understandable for all students, no matter their schooling or background.

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