Explain the following terms with one example each:
(a) Corrosion (b) Rancidity

Explanation

(a) Corrosion: It is a process of slow and gradual conversion of a metal into its undesirable compounds (sulphides, carbonates, oxides, etc.) by the attack of air and moisture (water) present in the atmosphere.
For example, reddish brown coating on iron, black coating on silver and green coating on copper are some examples of corrosion of iron, silver and copper respectively. Corrosion of iron is known as rusting.
(b) Rancidity: When the food items are kept for a long period, the fats and oils present in them get oxidised and their smell and taste change. They become rancid and so the process is called rancidity.
For example, rancid (decaying) flavour or smell in old cooking oil.