States of matter
Intermolecular space is the space between molecules. Intermolecular force is the force of attraction between molecules.
Gases have the largest intermolecular spaces because their particles are far apart.
Solid particles are held strongly by intermolecular forces, so they can mainly vibrate in fixed positions.
When a solid becomes a liquid, particles gain energy and can move more freely, so the effect of the intermolecular forces becomes less restrictive.
A gas has large spaces between particles, so the particles can be pushed much closer together.
The particles in a solid are held in fixed positions by strong intermolecular forces, so the solid keeps its shape.
Diffusion is faster in gases because gas particles move faster and have larger spaces between them.
When heated, particles generally move faster and the average intermolecular spaces increase.
A liquid keeps almost the same volume because its particles are still close together, even though they can move around.
Solid: particles close together, strong forces, vibrate in place.
Liquid: particles close together, weaker restrictions, move past each other.
Gas: particles far apart, weak forces, move freely.