Explain the term mixtures. Give an example of mixtures of - (a) two elements (b) two compounds (c) elements and compounds.

1. A mixture is an impure substance formed by mixing two or more kinds of substances (elements or compounds or both) physically in any proportion such that they do not undergo any chemical change.
2. For example, tap water is a mixture of water and some salts. Lemonade is a mixture of lemon juice, sugar, and water.
3. A mixture has no definite set of properties.
4. Its properties depend upon the constituents in which they are mixed together.
5. Thus, the properties of a mixture can be changed by changing the proportion of its constituents.
   

Example:

(a) Mixture of two elements: Brass is an example of a mixture of two elements, copper and zinc.

(b) Mixture of two compounds: Salt water is an example of a mixture of two compounds, salt (NaCl) and water (H₂O).

(c) Mixture of elements and compounds: Sulphur (S), carbon (C) and potassium nitrate (KNO₃) make gunpowder.