The process of changing water vapour into water is called condensation.

Explanation:

Chemical change: A chemical change occurs when one or more substances are converted into new substances with different chemical properties. In a chemical change, the chemical composition of the substances involved is altered, resulting in the formation of new substances.

Physical change: A physical change occurs when the form or appearance of a substance changes, but no new substances are formed. In a physical change, the chemical composition of the substance remains the same.

Options:

a) Rusting of iron: Rusting of iron is an example of a chemical change. When iron reacts with oxygen and moisture in the presence of air, it forms hydrated iron(III) oxide, commonly known as rust. The chemical composition of iron changes during this process.

b) Milk changes to curd: The conversion of milk to curd is an example of a chemical change. The process of curdling involves the action of bacteria or enzymes on milk proteins, resulting in the formation of curd. The chemical composition of milk changes during this process.

c) Digestion of food in our body: The digestion of food in our body is an example of a chemical change. The process of digestion involves the breakdown of complex food molecules into simpler substances through chemical reactions. The chemical composition of food changes during digestion.

d) Changing of water to water vapor: Changing water to water vapor is an example of a physical change, not a chemical change. When water is heated, it undergoes a phase change from a liquid to a gas, forming water vapor. The chemical composition of water remains the same during this process.

Conclusion:

The correct answer is option D, changing water to water vapor, as it is an example of a physical change and not a chemical change.