Explanation:

Digestion of food is a chemical change because it involves the breakdown of complex molecules into simpler ones through chemical reactions.

Chemical Change:
- Digestion is a process in which food is broken down into smaller molecules that can be absorbed and utilized by the body.
- It starts in the mouth with the mechanical action of chewing and the chemical action of saliva breaking down carbohydrates through the enzyme amylase.
- The food then travels to the stomach, where it is mixed with stomach acid and digestive enzymes, such as pepsin, to break down proteins.
- From the stomach, the partially digested food moves to the small intestine, where it is further broken down by enzymes from the pancreas, liver, and small intestine itself.
- Enzymes like amylase, lipase, and protease break down carbohydrates, fats, and proteins respectively into smaller molecules such as glucose, fatty acids, and amino acids.
- These smaller molecules can then be absorbed into the bloodstream and used by the body for energy, growth, and repair.

Physical Change:
- A physical change is a change in the state or form of matter without any change in its chemical composition.
- Digestion involves the breakdown of food into smaller molecules, but the chemical composition of the molecules remains the same.
- For example, the physical action of chewing breaks food into smaller pieces, but the chemical composition of the food molecules remains unchanged.
- Similarly, the mixing and movement of food in the digestive system are physical changes, as they do not alter the chemical composition of the food molecules.

Conclusion:
In conclusion, digestion of food is a chemical change because it involves the breakdown of complex molecules into simpler ones through chemical reactions. The physical actions involved in digestion, such as chewing and mixing, are considered physical changes as they do not alter the chemical composition of the food molecules.