Answer:
The molecules of a gas move apart when they collide. The average kinetic energy of the particles in a liquid (or solid) is small enough that the forces of attraction between them is sufficient to hold the particles close together. The molecules in a liquid (or solid) do not move apart.
Step-by-step explanation:
Gas – In a gas, particles are in continual straight-line motion. The kinetic energy of the molecule is greater than the attractive force between them, thus they are much farther apart and move freely of each other. In most cases, there are essentially no attractive forces between particles.