Chemistry (NTSE/Olympiad)  

2. Is Matter Around Us Pure


A mixture is a substance which consists of two or more elements or compounds not chemically combined together. All the solutions are mixtures. The various substances present in a mixture are known as “constituents of the mixture” or “components of the mixture”.
Example. Lemonade (nimbu pani) is a mixture of water, lemon juice, sugar and salt.
A mixture consists of two or more different type of particles having different chemical nature. Mixture may be homogeneous or heterogeneous. All the mixtures are impure substances. A mixture does not have a fixed composition or a fixed melting point and boiling point.
Types of mixtures
Mixtures are of two types :
(A) Homogeneous mixtures :
Those mixtures in which the substances are completely mixed together and are indistinguishable from one another, are called homogeneous mixtures.
All the homogeneous mixtures are called solutions.
Ex. A mixture of sugar in water (called sugar solution) is a homogeneous mixture because all the parts of sugar solution have the same sugar-water composition and appear to be equally sweet. There is no visible boundary of separation between sugar and water particles in a sugar solution.
(B) Heterogeneous mixtures
Those mixtures in which the substances remain separate and one substance is spread throughout the other substance as small particles, droplets or bubbles, are called heterogeneous mixtures.
Ex. The mixture of sugar and sand is a heterogeneous mixture because different parts of this mixture will have different sugar-sand compositions. Some parts of this mixture will have more of sugar particles whereas other parts will have more of sand particles. There is a visible boundary of separation between sugar and sand particles. The suspensions of solids in liquids are also heterogeneous mixtures. A mixture containing two (or more) immiscible liquids is also a heterogeneous mixture.

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