Particle theory

Fixed shape and position Fixed volume Closely packed particles which are dense and difficult to compress Strongest intermolecular forces

Fixed volume Takes the shape of its container Closely packed particles which are dense and difficult to compress Weaker intermolecular forces than solids

No fixed shape or volume Particles spread out and fill container Particles are far apart so easy to compress Weakest intermolecular forces

The movement of particles from an area of higher concentration to lower concentration

Because of Brownian motion - the random movement of particles due to their kinetic energy Only occurs in liquids and gases

Heating increases the rate of diffusion Gases have a faster rate of diffusion than liquids Particles with a lower molecular mass diffuse faster e.g. Cl (35.5) travels slower than Ammonia NH3 (17)

Place Potassium Manganate VII crystals in water This starts to diffuse and you can tell when it has stopped as the concentration of purple colour is the same throughout the container

Air sealed glass tubing On one side there is cotton wool soaked in ammonia solution and on the opposite end cotton wool soaked with hydrochloric acid Smoke will form closer to the hydrochloric acid as the ammonia has a lower Mr meaning it can travel further in a shorter period of time