CBSE Class 10 Answered

(i) The eating up of metals by the action of air, moisture or a chemical (such as an acid) on their surface is called corrosion.

For example: When an iron object is left in damp air (or water) for a considerable time, it gets covered with a red-brown flaky substance called rust. This is called rusting of iron.

(ii) The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called rancidity. It spoils the food materials prepared in fats and oils which have been kept for a considerable time and makes them unfit for eating.

For example: Potato chips are made in oil. On keeping them exposed for a long time, these chips start giving unpleasant smell and taste. They turn rancid.