Papers 1, 3 · Module
States of matter
Solids, liquids and gases
Everything is made of tiny particles that are always moving. In a solid they vibrate in fixed positions; in a liquid they are close together but slide past one another; in a gas they are far apart and move quickly in all directions. Heating gives particles more energy; at melting and boiling points that energy is used to overcome the forces between particles, so the temperature stays constant.
≈ 35 minDiffusion
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, caused by their random motion. Gases diffuse faster than liquids. Lighter particles (lower relative molecular mass) move faster at the same temperature, so they diffuse more quickly; higher temperature also speeds up diffusion.
≈ 25 min