Answer:
The liquid gains thermal energy.
The particles of liquid move faster.
The space between the liquid particles increases.
The liquid changes to a gas.
Explanation:
At the beginning, the liquid is heated, so it gains energy in the form of thermal energy. This gain in thermal energy translates into an increase in the average kinetic energy of the particles in a liquid: as a result, the particles move faster and faster, and because of that, the space between them also increases.
At a certain point, the distance between the particles in the liquid will become so large that particles will overcome the intermolecular forces that keep them closer to each other (and that were responsible for keeping the substance in a liquid state). When this occurs, the particles are completely free to move, and so the substance has became a gas.
