Is Matter Around Us Pure

MIXTURES
A mixture is a material containing 2 or more elements or compounds that are in close contact and mixed together in any proportion. The components of a mixture can be separated by simple mechanical means.
EX: i)  Air is a mixture if N, O, CO₂ , watervapour and a small amount of ther substances.
       ii) Gun powder is a mixture of nitre(KNO₃) sulphur and coal.

PROPERTIES OF MIXTURES:

1.A mixture homogenous or heterogenous. 
A homogenous mixture has uniform composition throughout its mass.
EX: Sugar solution is a mixture of sugar in water. Any portion of this solution contains the same proportion of sugar and water.

A heterogenous mixture of  does not have a uniform composition throughout its mass.
EX: a mixture of sand and common salt. The composition of different parts of this mixture have different proportions of sand and common salt.

2.The constuents of mixture can be separated by physical methods such as filtration, evaporation ,sublimation and magnetic separation.
EX: When a magnet is put in the mixture of iron filings and sulphur, the iron.
particles get attracted to the magnet. When we add carbon disulphide to the mixture, sulphur dissolves in it but iron particles remain unaffected. On filtration, iron can be obtained as aresidue.

3.In the preparation of a mixture , energy is usually neither given out nor absorbed.
EX: when sugar and sand is mixed together, there is no energy change, i.e., enrgy is neither released nor absorbed.

4.The composition of a mixture is not fixed.
EX: Composition of a mixture varies from one part to another. The constituents of the mixture may be present in any proportion by weight.

5.A mixture has no definite melting and boiling point etc.

6.In the formation of a mixture, no chemical reaction occure. The constituents of a mixture do not undergo any change in composition.

TYPES OF MIXTURES
Mixtures can be categorised into various types, depending on the physical states of the constituents. Some of these types are.

i)Solid-solid mixture, ex: sugar and sand

ii)Solid-liquid, ex: mixture of iodine and ethanol(tincture of iodine)

iii)Solid-gas ,ex: air trapped in pores of soil particles .

iv)Liquid-gas, ex: all gases are partially miscible with liquids.

v)Gas-gas, ex: air is a mixture of several gases.

vi)Liquid-liquid, ex: water-alcohol, water-oil mixture.