Explain how the size of molecules affects diffusion.

a) Size of molecules: Smaller molecules diffuse faster than larger molecules. This is because smaller molecules have less mass and encounter less resistance as they move through a medium, allowing them to spread out more quickly.

b) Type of medium: Diffusion occurs fastest in gases, slower in liquids, and slowest in solids. This is due to the arrangement and movement of particles in each state: particles in gases are far apart and move freely, in liquids they are closer but still mobile, and in solids they are tightly packed and vibrate in fixed positions.