Chemistry

Matter in Our Surroundings

Types of Mixtures

Mixtures are of two types :
1.Homogeneous mixtures, and
2.Heterogeneous mixtures.
Those mixtures in which the substances are completely mixed together and are indistinguishable from one another, are called homogeneous mixtures. A homogeneous mixture has a uniform composition throughout its mass. It has no visible boundaries of separation between the various constituents. 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. A mixture of two (or more) miscible liquids is also a homogeneous mixture. For example, a mixture of alcohol and water is a homogeneous mixture. Unpolluted air is a homogeneous mixture of gases like oxygen, nitrogen, argon, carbon dioxide and water-vapour, etc. All the homogeneous mixtures are called solutions. Some of the examples of homogeneous mixtures (or solutions) are : Sugar solution. Salt solution, Copper sulphate solution, Sea-water, Alcohol and water mixture, Petrol and oil mixture, Soda water. Soft drinks, Lemonade, Vinegar,Brass, Air, Kerosene oil, and Petrol. Please note that kerosene and petrol are not single substances, they are mixtures of various compounds of carbon and hydrogen (called hydrocarbons).
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. A heterogeneous mixture does not have a uniform composition throughout its mass. It has visible boundaries of separation between the various constituents. 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. For example, a suspension of chalk in water is a heterogeneous mixture. A mixture containing two (or more) immiscible liquids is also a heterogeneous mixture. For example, a mixture of petrol and water is a heterogeneous mixture. As we will learn after a while, all the suspensions and colloids are heterogeneous mixtures. Some of the examples of heterogeneous mixtures are : Sugar and sand mixture, Salt and sand mixture. Polluted air, Gunpowder, Milk, Ink, Petroleum, Paint, Glass, Coal, Soil, Wood,Blood, Starch solution, Soap solution, Iron filings and sulphur Mixture, Dyes, Petrol and water mixture,Chalk and water mixture, Muddy river water, Flour in water, Milk of Magnesia, Butter, Cheese, Face cream,Shaving cream, Hair spray, Fog and Mist. Most of the mixtures are heterogeneous, only solutions and alloys are homogeneous mixtures. We will now take one example to understand the characteristics of mixtures.

Notes

Matter in Our Surroundings - Notes

1. The Case of a Liquid Solute Dissolved in a Liquid Solvent