# Predicting physical states

### Melting, evaporating and boiling

must be transferred, by heating, to a substance for these changes of to happen. During these changes the gain energy, which is used to break or overcome:

• some of the between particles during
• all of the remaining bonds between particles during or boiling

Evaporation can take place below the of a substance. The rate of evaporation is at its maximum at the boiling point.

### Condensing and freezing

Energy must be transferred from a substance to the environment for and to happen. During these changes of state the particles lose energy as bonds form between the particles.

### Predicting a physical state

The state of a substance at a given temperature can be predicted if its and boiling point are known. The table summarises how to work this out.

ComparisonPredicted state
Given temperature < melting pointSolid
Given temperature is between melting and boiling pointsLiquid
Given temperature > boiling pointGas
Question

The melting point of oxygen is -218Ā°C and its boiling point is -183Ā°C. Predict the state of oxygen at -200Ā°C.

Oxygen will be in the liquid state at -200Ā°C (because this is between its melting and boiling points).