Rahul comes back from school. And as he enters his house, he smells that his mother has prepared his favourite dish. How is this possible?

Diffusion is the intermixing of particles of two types of matter.

When the food particles enter the air around the hot food, they have enough kinetic energy to move around and diffuse with the air away from the food too. This air circulates in the house and thus as Rahul comes back from school, he is able to smell his favourite dish.