Diffusion and osmosis are possible because of the nature of matter . We can define matter as anything that has mass and occupies space . It include living things and non living things around us.
Matter is made up of tiny particles which may be molecules or ions . These particles are moving from time to time. Matter exist in three states solid , liquid and gas.
In solid the particles are closely packed with very little space between them . The forces of attraction between the particles are very strong so that they cannot move around but vibrate in fixed position. In liquid the particles are not so closely parked together . They can move around but are still attracted to one another so that their movement are within a given space . In gas the particles move very fast. They are widely separated from one another and there is a very little attraction between them. Thus the difference between the three states of matter is the degree of movement of their particle.