CHEMISTRY

The branch of science that deals with the study of matter or chemicals. In chemistry we study composition, structure and properties of matter in detail.

SCOPE OF CHEMISTRY

Chemistry plays an important role in catering various human needs and aimed at improving the quality of life :

Food
Health care products
Polymers like terylene, nylon, and rayon.
Medicines
Soaps ,detergents, cosmetics.
Extraction of metals
Metals for jewelry like gold silver and titanium
Environmental issues
In making explosives like TNT,Dynamite,RDX etc.
In Harnessing Nuclear energy
Making of Fireworks
Other materials aimed at improving the quality of life

MATTER

Anything, which has mass and volume, is known as matter. E.g. stone, water, pen, chair etc.

Matter:Classification

It can be classified in two different ways:

I)PHYSICAL CLASSIFICATION

On the basis of physical state matter can be classified into following three types:

1) Solids:-

Substances having definite shape and definite volume are called solids.E.g. stone,chair.pen etc.

2)Liquids:-

Substances having definite volume but no definite shape are called liquids.E.g. water,oil,milk etc.

3)Gases:-

Substances having neither definite shape nor definite volume .E.g.air,hydrogen,oxygen etc.

II )CHEMICAL CLASSIFICATION

(I)ELEMENTS

An element is a pure substance which consists of only one kind of atoms.e.g. H,Na,Fe,Au,Ag etc.So far 118 elements have been discovered. Out of them 92 are naturally occurring and remaining 22 are man-made. So far as their physical states are concerned, two elements are liquid(Hg and Br),eleven exit as gases(H,N,O,F,Cl,He, Ne,Ar,Kr,Xe,Rn and Rn )and remaining 101 are solids at room temperature. Elements can further be subdivided into three types:

1.METALS

Those elements are called metals which:

possess lustre(shine).
good conductor of electricity.

are ductile and malleable.

are solids except mercury(Hg).

have high melting and boiling pt.
have high density.

are sonorous
have high tensile strength.

are electropositive in nature.

E.g. Li, Na,Fe,Au,Hg,Ag, etc

Non-Metals

Those elements are called non-metals which:

are dull.

brittle

bad conductor of heat and electricity.

exist in all the three states.

are electronegative in nature.

E.g. H,He,P,C,N,F,Cl etc.

III)-Metalloids

The elements having characteristics of both metals and non-metals are called metalloids. They are eight in number (B,Si,Ge,Ga,Sb,Te,Po and At).All of them are solids at room temperature.

II)COMPOUNDS

A compound is a pure substance which is formed by the combination of two or more elements in a fixed proportion by mass. E.g. water is a compound in which hydrogen and oxygen always combine in the simplified ratio of 1:8 by mass.Some other example of compounds are H₂O,CO,CO₂,HCl etc

COMPOUNDS:TYPES

I)Organic compounds

The hydrocarbons and their derivatives are included in this class of compounds .E.g.Methane,benzene,ethyl alcohol,acetone,ethers etc.

II)Inorganic compounds

The compounds other than hydrocarbons are called inorganic compounds.E.g. H₂O,CO,CO₂,HCl etc.

MIXTURES

A material is said to be mixture, if it is formed by mixing two or more substances in any proportion. E.g.air,milk,sea water, sugar in water, sand in water etc.

TYPES OF MIXTURES

1) HOMOGENEOUS MIXTURES

A mixture is said to be homogeneous if it has uniform composition throughout the sample. E.g. air, alloys, solution of sugar in water, solution of salt in water etc. True solutions belong to the category of homogeneous mixtures in which size of the particles is less than one nanometer.

2)HETEROGENEOUS MIXTURES

A mixture is said to be heterogeneous if it does not have uniform composition throughout the sample.E.g.sand in water, gun powder ,suspensions like blood,paints,spray etc.Colloids and Suspensions belong to the category of heterogeneous mixtures. In colloids particle size rages from 1nm to 1000nm and in suspension particle size is greater than 1000 nm.

DIFFERENCE: COMPOUNDS AND MIXTURES

Compound	Mixture
1) It has constant composition.	1) It has variable composition.
2)They are always homogeneous in nature.	2) It may be homogeneous or heterogeneous.
3) Compound is formed by a chemical change.	3) It is formed by a physical change.
4) Its formation is accompanied by some energy change	4)Generally no energy change occurs during its formation.
5)It has a sharp melting and boiling points.	5)It does not have sharp melting and boiling points.
6) Its constituents lose their identity.	6) Its components do not lose their identity.
7) Its elements can be separated only by chemical methods.	7) Its components can be separated by simple physical methods