How do solid and liquid water change to water vapour?

Answer 1

Sufficient energy is added to the molecule to break the inter-molecular bonds.

First, in a solid, as energy is added, the bonds absorb the energy, and move more vigorously. So our solid heats up, and eventually, the bonds are broken completely free. We now have a liquid.

As energy is added to the liquid, individual molecules absorb enough energy to break free of the surface, and evaporate off into space.

Answer 2

Solid water (ice) changes to water vapor through a process called sublimation, where the ice transforms directly into vapor without melting first. Liquid water evaporates into water vapor when heated, as the molecules gain enough energy to break free from the liquid phase and enter the gaseous phase.