Question

Why particles of one type of matter diffuse into particles of other?

Answer 1

While making a solution, we add solute into solvents. These two type of particles can have many types of forces like
intermolecular, ionic and Van der Waal forces . Due to these forces, depending on the nature of solutes and solvents, solid particles dissociates into liquid and occupies the free spaces among the particles. For example, in ionic compounds like NaCl, the salt dissociates in Na+ and Cl-, which forms bonds with the water molecules. Also, only polar substances dissolves in polar solvents (Water is a polar substance) and non polar dissolves in non polar (Benzene is non polar)

Answer 2

This is due to 2 characterstic of particles of matter..   :
1) Particles of matter have spaces between them
2) Particles of matter are continuosly moving

When particles of matter mix with air then it travel from one place to another and that's what we call "DIFFUSION" 

Hope this helps...!!!