Freezing of water is not a chemical change because it can be reversed . Ice cube (freezed water) can again be converted into water by supplying heat to it . When heat is supplied to ice cube , it will change into water .So , changing of states from solid to liquid or vice versa is a physical change and not a chemical change.

Introduction:
Chemical changes refer to the process in which substances undergo a transformation that results in the formation of new substances with different chemical properties. In contrast, physical changes do not involve the formation of new substances and only affect the physical characteristics of the material. In this context, we will analyze the given options to identify the correct answer.

Explanation:
Let's examine each option to determine if it represents a chemical change or not:

a) Rusting of iron:
Rusting of iron is a chemical change. It occurs when iron reacts with oxygen and water in the presence of moisture, leading to the formation of iron oxide (rust). The original iron is transformed into a new substance with different chemical properties.

b) Cooking of food:
Cooking of food is also a chemical change. During cooking, various chemical reactions occur, such as denaturation of proteins, caramelization of sugars, and Maillard reactions. These reactions result in the formation of new compounds, altering the taste, texture, and appearance of the food.

c) Freezing of water:
Freezing of water is a physical change, not a chemical change. When water freezes, it undergoes a phase change from a liquid to a solid state without any alteration in its chemical composition. The water molecules arrange themselves in a regular pattern to form ice, but the substance remains H2O.

d) Digestion of food:
Digestion of food is a complex process that involves both physical and chemical changes. It primarily refers to the breakdown of food into smaller molecules that can be absorbed and utilized by the body. Enzymes in the digestive system catalyze various chemical reactions to break down proteins, carbohydrates, and fats into simpler compounds. Therefore, digestion of food represents a chemical change.

Conclusion:
Among the given options, the freezing of water (option c) is the only example of a physical change rather than a chemical change. The other options, such as rusting of iron, cooking of food, and digestion of food, all involve chemical reactions and the formation of new substances.