Question

Explain what causes a change of state. Be sure to include what is happening with the molecules.

Answer 1

Ah, intermolecular forces either weaken or strengthen, causing the molecules to either spread further apart (as in a liquid or a gas) or condense into a more solid state.

Answer 2

As temperature increases, for example, the kinetic energy per atom or molecule increases, leading to greater and greater motion, solid bonds are disrupted and the molecules become random but still close, forming a liquid, higher temperatures eventually cause the molecules to break free from each other and become gaseous.