Diffusion

Have you ever noticed how the smell of cookies baking in the kitchen spreads throughout the house? That’s diffusion! The particles that make up the smell move through the air to areas with less concentrated smell.

This process is called diffusion.

Here, molecules naturally move from areas of high concentration to areas of low concentration without utilizing energy.

Oxygen delivery in the human body is another example of diffusion. After we inhale, oxygen is absorbed into the bloodstream, increasing its concentration.

Meanwhile, the cells in the body constantly use oxygen for energy production. As a result, their oxygen concentration decreases.

Due to the concentration difference, oxygen moves from the blood, where it's in high concentration, into the cells, where it's in lower concentration.

This diffusion continues until oxygen inside the cells matches the concentration outside. This balance is called equilibrium.

Even at equilibrium, oxygen molecules continue to move in and out of the cells, but the rate of movement is equal in both directions.