Evaporation can take place below the boiling point of a substance. The rate of evaporation is at its maximum at the boiling point.
The state of a substance at a given temperature can be predicted if its melting point and boiling point are known. The table summarises how to work this out.
|Given temperature < melting point||Solid|
|Given temperature is between melting and boiling points||Liquid|
|Given temperature > boiling point||Gas|
The melting point of oxygen is -218°C and its boiling point is -183°C. Predict the state of oxygen at -200°C.
Oxygen will be in the liquid state at -200°C (because this is between its melting and boiling points).