Lesson 6 - Changes of State

Specific Heat Capacity

of a substance is the amount of energy required to raise the temperature of 1 kg of the substance by 1K or 1 ºC

§When a substance is heated, its temperature rises causing the particles within it to gain kinetic energy.

§The amount of energy required to raise the temperature of a substance is given by its specific heat capacity. 

Low specific heat capacity

a substance warms up and cools down quickly as it takes much less energy to change its temperature.

High specific heat capacity

a substance warms up and cools down slowly as it takes much more energy to change its temperature.

Gas → liquid

Condensation

Solid → gas

Gas → solid

Sublimation

specific Latent Heat

is the amount of energy required to change the state of 1 kg of the substance with no change in temperature.

Latent Heat

§When a substance changes state, there is no temperature change.

§The energy supplied to change the state is called the latent heat.

§When a change of state involving heating occurs, such as boiling or melting, this energy supplied to the system increases the internal energy.

  The energy is being used to break apart the bonds between particles

in the substance and is not increasing the temperature.

§When a change of state involving cooling occurs, such as condensation or freezing, the system decreases in internal energy.

The energy is being released to make bonds between the particles.

Specific latent heat of vaporisation (boiling

othis is the energy needed to change a substance from liquid to gas without changing its temperature.    

Specific latent heat of fusion (melting)

this is the energy needed to change a substance from solid to liquid without changing its temperature.