Chemistry

Introduction To Chemistry
Chemistry is the branch of science which deals with the composition, preparation and properties of elements,compounds and other substances.It also deals with different kinds of chemical reactions.

Branches of chemistry

There are seven branches of chemistry. These are,

(a). Inorganic chemistry : It deals with metals and non- metals, their properties and reactions.

(b). Organic chemistry : It deals with different measurements and instruments.

(c). Organic chemistry : It deals with carbon and its compounds; benzene and its derivatives.

(d). Biochemistry : It is that branch of chemistry which deals with biomolecules and their properties.

(e). Analytical chemistry : It is that branch of chemistry which deals with the composition, preparation and properties.

(f). : Industrial chemistry : It is that branch of chemistry which deals with the chemicals of industrial applications.

(g) : Agricultural chemistry : It is that branch of chemistry which deals with the substances of agricultural utility like fertilizers, pesticides etc.

ROLE OF CHEMISTRY

            Chemistry is playing very important and pivotal role in human life. Some vital roles played by chemistry are as follows:

         I.      Birth controlling drugs are proving very important in population control. Population control will solve major problems of the nation, mainly of food and shelter.

                II.      New fertilizers and insecticides developed in agricultural chemistry have proved very useful in improving the crops and increasing yield.

             III.      Wines and beers are being produced by new methods of chemistry.

             IV.      Many medicines developed under the expanding dimensions of chemistry have saved men from dreadful diseases. Vitamins, hormones etc. are proving very useful.

        V.      Industrial chemistry has proved very useful in producing new soaps, detergents, cosmetics etc.

             VI.      We see a revolution in our daily life in the consumer’s products due to chemistry.

FOUNDERS OF CHEMISTRY

            Lavoisier and Robert Boyle are considered as founders of modern chemistry.

Lavoisier

Robert Boyle

In fact chemistry is born from alchemists who tried to make gold from ordinary metals and elixir. These chemists could not make elixir or gold but as a result, chemistry and its branches were developed. The chemists gave to the world new type of experiments and new methods of fabrication. Industrial revolution has resulted because of physics and chemistry. 

ATOMS AND ATOMIC STRUCTURE

Matter : It is defined as anything that has mass and occupies space. Everything in universe is made of matter.

Matter can be divided in to 3 main physical states.

COMPARISON OF MAIN PHYSICAL STATES

PROPERTIES	SOLID	LIQUID	GAS
Arrangement of particles	Tightly packed	Loosely bonded	Far apart
Inter particle attraction	Very strong	Relatively weak	Very weak
Movement of particles	Vibration at a mean position	Flow	Randomly motion
Volume	Definite	Definite	Indefinite
Shape	Definite	Indefinite	Indefinite
Compressibility	Least	Moderate	Higher

ATOMIC THEORY – John Dalton (1808)

1. The smallest particle of matter is called “atom”
2. Atom is indivisible and non creatable.
3. Atoms in an element are exactly same. Atoms in different elements are completely different.
4. Elements are combined to form compounds. The ratio of elements in a compound is simple and whole numbered.

CORRECTIONS TO ATOMIC THEORY

1. Atom is not the smallest particle because there are subatomic particles such as    electrons, protons, neutrons etc. But the smallest unit of matter is atom.
2. Atoms are divisible and creatable in nuclear reaction. As an example Chadwick discovered neutrons by following nuclear reaction.

          

         ⁹₄Be  +  ⁴₂He  -----> ¹²₆C   +   ¹₀N

But atoms are not divided or created in a chemical reaction. Therefore chemical equations can be balanced according to atom.

      NaOH  +  HCl  -----> NaCl   +   H₂O

3. There are different atoms in the same element according to mass called Isotope.

11H	21H	31H
p = 1	p = 1	p = 1
e = 1	e = 1	e = 1
n = 0	n = 1 (Deuterium)	n = 2 (Tritium)

      

        

There are similar atoms in different elements according mass called Isobars.

              Examples: -     ¹⁴₆C   ,    ¹⁴₇N

4. In some compounds ratio of element is not simple.

                    Examples: -    Tar – C₅₀H₁₀₂

                                                  Octane – C₈H₁₈