The three states of matter are solid, liquid and gas.
When ice (a solid) melts, it turns into water (a liquid); this is called fusion. When water (a liquid) boils, it turns into steam (a gas); this is called vaporisation.
When steam (a gas) turns into water (a liquid); this is called condensation. When water (a liquid) freezes, it turns into ice (a solid); this is called freezing.
When a substance changes from one state to another, the temperature remains constant. For example, when heat energy is added to ice at its melting point ( ), it changes into the same mass of water at .
A solid substance at its melting point has less energy than the same mass of the substance when it is a liquid at the same temperature.
To change a solid into a liquid, or a liquid into a gas, requires heat energy. This heat energy allows the change of state to happen, and the temperature remains constant during the process.
The amount of energy required to change the state of a substance depends upon the mass and characteristics of that substance.
The energy required to change the state of a material is known as the latent heat.
The amount of energy required to change the state of of that material is known as the specific latent heat of that substance.
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