Give reason for each of the following:
(i) Ripening of a fruit is a chemical change.
(ii) Crystallization of a substance from its solution is a physical change.
(iii) Formation of curd from milk is a chemical change.
(iv) Separation of gases from air is a physical change.
(i) Composition and properties of fruit initially are entirely different than those after ripening of fruit. It cannot be reversed. Hence, it is a chemical change.
(ii) Crystallization of a substance is a physical change because there is no change in composition and chemical properties of the substance. The crystallized substance can again be made into solution.
(iii) Curd and milk have entirely different properties and curd cannot be changed to milk. Hence it is a chemical change.
(iv) Separation of gases from air is a physical change because separated gases can again be mixed.
