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SAI International School
Subject-Chemistry
Ch-Is Matter around us pure?
Topic-Pure and Impure substances

LESSON NOTE

Pure substances: In pure substance all the constituent particles are same in their
chemical nature or properties. A pure substance consists of only one type of particles.

A substance is a kind of matter that cannot be separated into other kinds of matter by
any physical process and its composition is same throughout.

Characteristics of pure substances:

 They are composed of same kind of particles

 They are homogeneous
 They cannot be separated into any other kinds of matter by physical processes.

 They have fixed composition throughout.

 They have fixed properties throughout.
 They have fixed melting and boiling points

 Examples: Elements and compounds

Impure substances or mixtures: In impure substances all the constituent particles are
not same. The impure substances or mixtures consists of different types of particles.

Characteristics of impure substances or mixtures:

 They are composed of different kind of particles
 They may be homogeneous or heterogeneous

 They can be separated into any other kinds of matter by physical processes.

 They do not have fixed composition throughout.
 They do not have fixed properties throughout.

 They do not have fixed melting and boiling points

 Examples: Mixtures