The student conducted experiments to study the diffusion of solids in liquids. They found that (1) when solids like copper sulfate come into contact with water, diffusion occurs as intermixing of the substances, (2) the rate of diffusion increases with increasing temperature, and (3) smaller solid particles diffuse more quickly than larger particles. The experiments demonstrated how temperature, particle size, and other factors influence the rate at which solids diffuse into liquids.