If heat is absorbed by a one kilogram block of lead, the particles gain energy. Since lead is a solid and the particles are only vibrating, they vibrate faster after being heated. As the particles are closer together in a solid, they are more likely to hit each other and pass the energy around.
This means that the energy spreads through the block quickly and the temperature of the block goes up quickly. It takes less energy to raise the temperature of a one kg block of lead by 1°C than it does to raise the temperature of one kg of water by 1°C.
From this it can be seen that a change in temperature of a system depends on:
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 one kg of water by 1 °C.
Some other examples of specific heat capacities are:
|Material||Specific heat capacity (J/kg/°C)|
Because it has a low specific heat capacity, lead will warm up and cool down quickly as 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 stay warm for a long time. Most heaters are filled with oil (1,800 J/kg/°C). Radiators in central heating systems use water (4,200 J/kg/°C) as they need to stay warm for a long time, so must have a lot of energy to lose.
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:
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
How much energy is lost when 2 kg of water cools from 100°C to 25°C?
How hot does a 3.5 kg brick get if it is 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