Have you ever wondered how perfume sprayed across the room travels to where you are sitting? This happens through a process called diffusion. Diffusion happens when a substance moves from an area of high concentration to an area of low concentration. Gases and liquids are often the particles that undergo diffusion because their particles move randomly and quickly. Diffusion is a very important process for living things in our world today. This is because substances move in and out of cells through diffusion.

An example of diffusion is when you make a cup of coffee with hot water. When coffee is put in water, the coffee molecules are highly concentrated. The molecules in the coffee start to spread in between the water molecules. Now through diffusion, the coffee molecules will be in a lower concentration compared to when the coffee was just put in the hot water. Diffusion happens because gases and liquids move from place to place in quick random motions. When this happens, the particles collide, which in turn makes them change directions. The process of diffusion occurs on its own without any help from shaking or stirring. However, solids will not undergo diffusion because the particles are very tightly packed together.