Question

Differentiate between:
(a) Pure and impure substances
(b) Homogenous and heterogenous substances.

Answer 1

Hint: The substances can be differentiated on the basis of the composition of the component present in them. The substances can be in the form of an element or compound and in a mixture. Depending on the composition, the various types of mixture show distinct characteristics.

Complete step by step answer:
(a) Pure and impure substance
Pure substances:
(i) Pure substances possess specific composition and their physical properties and the chemical properties also remain the same.
(ii) Pure substance has sharp melting and boiling point.
(iii) Pure substances are homogeneous in nature which means their composition remains the same throughout the bulk.
(iv) Examples of pure substances are elements and compounds.
Impure substances:
(i) The composition of the impure substance is not fixed. The impure substance is formed of two or more than two pure substances.
(ii) The temperature of impure substances has a range at which they melt or boil.
(ii) Impure substances may be homogeneous in nature or heterogenous in nature which means its composition changes.
(iii) Examples of impure substances are air, petroleum, sugar solution in water.
(b) Homogenous and heterogenous substances.
Homogeneous substances
(i) Homogeneous substances are defined as the substances which are formed by the uniform distribution of the component which combine to form the substance.
(ii) Example of homogeneous substances: air, rain water, sugar solution.
Heterogeneous substances
(i) Heterogeneous substances are defined as the substances which are formed by the non-uniform distribution of the component which combine to form the substance.
(ii) Example of homogeneous substances: Cereal in milk, vegetable soup.


Note: The homogeneous substance has only one phase while the heterogeneous substance has two or more than two phases. The heterogeneous and homogeneous substance come under impure substance as they are formed of more than two components.