Question

Difference between :

(a) Pure and impure substances

(b) Homogeneous and heterogeneous substances

Answer 1

(a) Pure substances —
1. Pure substances have de nite composition and de nite physical and chemical properties.
2. They are all homogeneous i.e. their composition is uniform throughout the bulk.
3. Examples: Elements and compounds.
Impure substances —
1. Impure substances are made up of two or more pure substances mixed together in any
proportion.
2. They may be homogeneous or hetergeneous i.e. their composition is not uniform throughout the
bulk.
3. They are all mixtures.
Examples: air, sea water, petroleum, a solution of sugar in water are all impure substances.
(b) Homogeneous mixture — is a mixture where the components that make up the mixture are uniformly distributed throughout the mixture.
Example — air, sugar water, rain water.
Heterogeneous mixture — is a mixture, where the components of the mixture are not uniform or have localized regios with different properties.
Example—Cereal in milk, vegetable soup.