When a substance changes state, it does not change into a new substance. Ice is still water – it is water in the solid state. Steam is still water – it is water in the gaseous state. Th e heat has not broken down the water into hydrogen and oxygen gases. Any substance can exist in any state, if it is cooled or heated enough.
E.g. If nitrogen gas is cooled to -195.79°C, it will change to a liquid. If this is cooled further to -210°C, the liquid nitrogen will solidify.
E.g. Iron will melt to a liquid above 1538°C. Th is liquid iron will change to a gas above 2862°C. The temperature at which a solid changes to a liquid is called the melting point.
The temperature at which a liquid changes to a gas is called the boiling point.
