Digestion is the process that breaks down food into small molecules so that it can be absorbed into the bloodstream and then transported across the cell membrane to be used by cells. Unused molecules pass out of the body as waste. Digestion is both mechanical and chemical. Mechanical digestion changes the physical form of food and involves physical change. Chemical digestion changes the composition of food and is therefore a chemical change.

Watch the following video to learn more about physical and chemical changes in the digestive system.

Let’s see what you have learned. The following animation traces a piece of food from the mouth to the large intestine. Along the way, you will be asked to decide if the digestion taking place is an example of a physical or chemical change.