Diffusion is the movement of molecules (gas, minerals and particles) from an area of higher concentration to an area of lower concentration. Diffusion is an important process that occurs within the cells of plants and animals. One example of diffusion is the exchange of oxygen and carbon dioxide during respiration. When we breathe in oxygen there is a higher concentration of oxygen in our lungs than in our circulating red blood cells, so oxygen diffuses across cell membranes from our lungs into our blood vessels and into our red blood cells to be distributed throughout our body. The reverse happens with carbon dioxide that we exhale. The carbon dioxide is more concentrated in our red blood cells (carbon dioxide is a by-product of cellular respiration – which we will study next) and is diffused into the lungs (lower concentration) and then we exhale releasing carbon dioxide into the environment. This carbon dioxide is taken in by plants to be used in photosynthesis.
Another example of diffusion is when nutrients are taken into a plant. Plants utilize nutrients to grow and live and these nutrients are obtained by diffusion. Since nutrients are more concentrated in the soil around the roots, they diffuse into the roots and are carried throughout the plant to the various cells.
Materials needed: 
1 tube of food coloring (darker colors work best, but any color will do)
1 large, clear drinking glass or similar container
Water (from your faucet)
Procedure:
1. Fill glass container almost to the top with cold water.
2. Drop 3-4 drops of food coloring into the water.
3. Observe for 2-3 minutes – taking photos to record the progress.
4. Record your observations. How do you think diffusion helps nutrients, waste and other molecules move around the cell?