Question

question 8
what happens to the molecules of a substance as it changes from a liquid to a gas?
the molecules lose all motion
the molecules slow down and become more ordered
the molecules speed up and move farther apart
the molecules become more tightly packed.

Explanation:

When a substance changes from liquid to gas (vaporization), heat energy is added. This increases the kinetic energy of the molecules, making them move faster (speed up). In a liquid, molecules are close but can move past each other. In a gas, the intermolecular forces are weaker, so molecules move freely and are much farther apart compared to the liquid state. The other options are incorrect: molecules don't lose all motion (as there's always some molecular motion unless at absolute zero), they don't slow down and become more ordered (that would be for a liquid - to - solid change like freezing), and they don't become more tightly packed (which would also be a characteristic of a phase change towards a more condensed state like liquid to solid).

Answer:

The molecules speed up and move farther apart