Diffusion is the movement of particles from areas of higher concentration to areas of lower concentration. It is a natural, random process. This means that it does not require extra energy input. 1. These are pictures of molecules frozen at two different times. Which diagram depicts “before” diffusion occurs?

A. B.

2. Diagram A shows the same number of particles as in Diagram B except most particles start out on one side of the box. Explain why after a while, Diagram A resembles Diagram B.

Give an everyday example of diffusion in air and in water.

3. AIR:

4. WATER:

5. Complete the following sentence: Diffusion is the movement of particles from concentration to a concentration until they are spread out.

6. Moths emit chemicals called pheromones to attract a mate.

a) Which process is responsible for the distribution of these chemicals through the air?

b) If a moth detects pheromones, how might it work out which direction they are coming from?

c) What would be the advantage of a moth releasing the pheromones on a night when there was little wind?