Chemical Reactions and Equations — Question 20

(a) Corrosion — When a metal is attacked by substances around it such as moisture, acids, etc, it is said to corrode and this process is called corrosion.
For example, iron articles are shiny when new, but get coated with a reddish brown powder when left for some time due to rusting.

(b) Rancidity — When taste and smell of food items containing fat and oil change due to oxidation, then this condition is called rancidity.
For example, when butter is left exposed to air for a long time, it becomes rancid, making it unsuitable for consumption and cooking.