Changes in a material's temperature or state of matter are caused by changes to the internal energy. The energy required by different materials depends on their 'heat capacity' and 'latent heat'.

If 1,000 J of heat is absorbed by a one kilogram block of lead, the particles gain energy and the temperature of the block rises. If a one kilogram block of lead absorbs 2,000 J of energy then the temperature rise will be larger.

If 1,000 J of heat is absorbed by a 2 kg block of lead then the temperature of the block doesn’t rise as much since the energy is shared between more particles. If 1,000 J of energy is absorbed by a one kilogram block of copper instead of lead then the temperature of the block doesn’t rise as much.

From this it can be seen that a change in the temperature of a system depends on:

- the mass of the material
- the substance of the material - its specific heat capacity
- the amount of energy put into the system

The specific heat capacity of a material is the energy required to raise one kilogram (kg) of the material by one degree Celsius (°C).

The specific heat capacity of water is 4,200 joules per kilogram per degree Celsius (J/kg°C). This means that it takes 4,200 J to raise the temperature of 1 kg of water by 1°C.

Some other examples of specific heat capacities are:

Material | Specific heat capacity (J/kg°C) |
---|---|

Brick | 840 |

Copper | 385 |

Lead | 129 |

Because it has a low specific heat capacity, lead will warm up and cool down faster because it doesn’t take much energy to change its temperature.

Brick will take much longer to heat up and cool down. Its specific heat capacity is higher than that of lead so more energy is needed for the same mass to change the same temperature. This is why bricks are sometimes used in storage heaters, as they store a large amount of energy and emit it over a long period of time. Most heaters are filled with oil (1,800 J/kg°C) and where there is central heating, radiators use water (4,200 J/kg°C).

The amount of thermal energy stored or released as the temperature of a system changes can be calculated using the equation:

change in thermal energy = mass × specific heat capacity × temperature change

This is when:

- change in thermal energy ( ) is measured in joules (J)
- mass (
*m*) is measured in kilograms (kg) - specific heat capacity (
*c*) is measured in joules per kilogram per degree Celsius (J/kg°C) - temperature change ( ) is measured in degrees Celsius (°C)

How much energy is needed to raise the temperature of 3 kg of copper by 10°C?

The specific heat capacity for copper is 385 J/kg°C

- Question
How much energy is lost when 2 kg of water cools from 100°C to 25°C?

- Question
How hot does a 3.5 kg brick get if it's heated from 20°C by 400,000 J (400 kJ)?

final temperature = starting temperature + change in temperature

final temperature = 20 + 136

final temperature = 156°C