Melting, boiling and evaporation Flashcards – Cambridge IGCSE (9–1) Physics 0972 (Extended) (2026–2028)

What changes of state occur in melting and solidification?

Melting: solid to liquid.
Solidification: liquid to solid.

What does energy supplied to a pure substance at its melting temperature do to its particles?

It overcomes some attractions holding the particles in fixed positions, changing their arrangement.

What happens to the temperature of a pure substance while it melts?

It remains constant.

At what temperature does pure water melt at standard atmospheric pressure?

$0\,{}^\circ\mathrm{C}$

How does particle behaviour change as a liquid loses energy and solidifies?

The particles become arranged in fixed positions, where they vibrate rather than moving freely past one another.

What is boiling?

The change from liquid to gas throughout a liquid, with gas bubbles forming within it.

Why does a pure liquid’s temperature remain constant while it boils at fixed pressure?

The energy supplied separates its particles rather than raising its temperature.

At what temperature does pure water boil at standard atmospheric pressure?

$100\,{}^\circ\mathrm{C}$

What change of state is condensation?

The change from gas to liquid.

What happens to gas particles’ energy and speed during condensation?

They lose energy and move less rapidly.

What brings particles closer together during condensation?

Attractions between the particles.

How are particles arranged, and how can they move, in the liquid formed by condensation?

They remain close together but can move past one another.

What is evaporation?

The escape of more-energetic particles from a liquid’s surface, becoming gas particles.

Can evaporation occur below a liquid’s boiling temperature?

Yes.

Why does evaporation cool a liquid?

Escaping particles carry away energy, lowering the average kinetic energy of the particles remaining in the liquid.