This Kapow pupil video is part of the Kapow Science scheme of work. Melting is when a solid changes into a liquid, and freezing is the reverse – a liquid changing into a solid. Melting requires heat, while freezing happens when a liquid is cooled below its freezing point. For example, water freezes into ice at 0°C and melts back into liquid at the same temperature. These processes are opposites and happen at the same point for each material.

Different materials have different melting and freezing points. Copper, for example, stays solid at room temperature because it melts only at 1085°C, while oxygen freezes at -218.8°C. The state of a material depends on whether it is above its melting point or below its freezing point. We can also change these points by adding other materials – for instance, mixing salt with ice lowers water’s freezing point, helping to prevent roads from icing over and melting snow that has already fallen.

The video is designed to be shown to pupils as part of Science, key stage 2, Year 4, Materials: States of matter, Lesson 3: Melting and freezing