Which of the following are chemical changes? I. cooking of food II. digestion of food III. freezing of water IV. water is heated up

I and II are chemical changes. A chemical change is a transformation in which a substance undergoes a chemical reaction to form a new substance with different properties. Cooking of food and digestion of food are examples of chemical changes because the chemical composition of the food changes as it is cooked or digested. Freezing of water is a physical change, not a chemical change. Freezing is a change of state from a liquid to a solid, but the chemical composition of the water remains the same. Heating of water is also a physical change, not a chemical change. Heating causes the water molecules to move faster, but the chemical composition of the water remains the same.