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

Explanation

(a) Corrosion: The slow eating up of metals by the reaction of some atmospheric gases like oxygen, carbon-dioxide or water vapour is known as corrosion .
E.g : The copper articles get coated with green colour which is due to the formation of basic copper carbonate .
(b) Rancidity : Rancidity may be defined as the natural oxidation of the oils and fats, which are present in food items , giving bad smell and taste .
E.g. : Food items, containing fats and oils, give bad smell when they exposed to air for a long time .