Diffusion

If you drop food coloring into water, the color slowly spreads until the whole glass is colored. This is diffusion. Particles naturally move from crowded areas to less crowded areas. Diffusion happens in liquids, gases, and even through solid membranes. It does not need any energy to push it along.

How Diffusion Works

All particles are constantly moving and bouncing around. In a crowded area, they bump into each other and spread out. Over time, the particles spread evenly throughout the space. This is why perfume sprayed in one corner of a room can eventually be smelled everywhere. The perfume molecules diffuse through the air.

Diffusion in Your Body

Diffusion is essential for life. In your lungs, oxygen diffuses from the air into your blood. Carbon dioxide diffuses from your blood back into the air you breathe out. In your cells, nutrients diffuse in and waste products diffuse out. Without diffusion, your cells could not get the oxygen and food they need.

Fun Facts

• Diffusion happens faster in hot liquids than in cold ones because the particles move faster.
• A tea bag works by diffusion. Tea particles spread from the bag into the surrounding water.
• It would take years for a smell to diffuse across a large room if there were no air currents.

Did You Know?

If you could watch molecules with a super-powered microscope, you would see them bouncing around randomly in all directions. This random bouncing is called Brownian motion, and it is what drives diffusion!