1. Diffusion

2. Diffusion is…
… the spreading out of a gas or liquid as their particles move and mix.
diffusion only takes place if there is a difference in concentration of the substance. This is known as the concentration gradient.
the substance moves from high concentration to an area of lower concentration.
the higher the concentration gradient the faster the rate of diffusion.
small molecules diffuse more quickly than large ones.

3. Diffusion
In your Lungs

5. High concentration of CO2 in blood
Low concentration of CO2 in air
High concentration gradient
CO2 diffuses from blood to air
Animation from BBC Bitesize

6. High concentration of O2 in air
Low concentration of O2 in blood
High concentration gradient
O2 diffuses from air to blood
Animation from BBC Bitesize

7. Diffusion
In your Intestine

9. High concentration of glucose in intestine
Low concentration of glucose in blood
High concentration gradient
Glucose diffuses from intestine to the blood

10. Diffusion
Into cells

11. High concentration of glucose and O2 in blood
Low concentration of glucose and O2 in cell
High concentration gradient
Glucose and O2 diffuses from blood into the cell