(a) Pure and impure substances
(b) Homogenous and heterogenous substances
(a) Pure substances —
- Pure substances have definite composition and definite physical and chemical properties.
- They are all homogeneous i.e. their composition is uniform throughout the bulk.
- Examples: Elements and compounds.
Impure substances —
- Impure substances are made up of two or more pure substances mixed together in any proportion.
- They may be homogeneous or hetergeneous i.e. their composition is not uniform throughout the bulk.
- 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.