Class IX, CHEMISTRY, "Introduction to Chemistry"

CHEMISTRY 

The branch of science which deals with the composition and properties of matter, changes in matter and the laws or principles which govern these changes is called Chemistry.

BRANCHES OF CHEMISTRY

1.            Physical Chemistry

It is the branch of chemistry that deals with the law and the principles governing the combination of atoms and molecules in chemical reactions.

2.            Inorganic Chemistry

The study of all elements and their compounds except carbon is called inorganic chemistry.

OR

It is the branch of chemistry that deals with chemistry of elements and their compounds, generally obtained from non-living organisms i.e. from minerals.

3.            Organic Chemistry

The branch of chemistry in which we study the compounds of carbon is called organic chemistry.

4.            Analytical Chemistry

It is the branch of chemistry that deals with the study of the methods and techniques involved to determine the kind, quality and quantity of various components in a given substance

5.            Biochemistry

The study of chemical compounds present in living things is called biochemistry.

6.            Industrial Chemistry

The application of chemical knowledge in technology and industry and the preparation of industrial products are called industrial chemistry.

 

7.            Nuclear Chemistry

It is the branch of chemistry that deals with the study of changes occurring in the nuclei of atoms, accompanied by the emission of invisible radiations.

8.            Environmental Chemistry

It is the branch of chemistry that deals with the study of the interaction of chemical materials and their effect on the environment of animals and plants.

9.            Polymeric Chemistry

 It is the branch of chemistry that deals specially with the study of polymerization and the products obtained through the process of polymerization such as plastics, synthetic fibers, paper etc.

STEPS INVOLVED IN GETTING INFORMATION IN THE SCIENTIFIC METHOD

Science is not only an integrated knowledge of physical and biological phenomena but also the methodology through which this knowledge is gathered. The process of scientific discoveries is a cyclic process.
In science the facts are gathered through observations and experiments and then theories or law are deduced. The scientific method include following four steps:
 

1. Observation
2. Inference
3. Prediction
4. Experiment

1. Observation

The observations are made by the five senses of man. Men made equipments are also used for making observations. For example microscope is used for observing minute objects. Thermometer is used to measure temperature. Sensitive balance is used to determine the mass of a very light object. The capacity of man made instruments is also limited. But it can be improved by improving technology. Thus better and more reliable information are given to the scientists who produce better result. Information acquired through careful observations are called facts. These facts are foundation of scientific knowledge.

2. Inference

The facts gathered through observations are carefully arranged and properly classified. Correlating the knowledge thus acquired with previous knowledge, we try to think of a tentative solution to explain the observed phenomenon. The tentative solution is called hypothesis. The validity of this hypothesis is tested through the results obtained from experiments. The results are discussed by the scientists and the hypothesis is accepted or rejected. The accepted hypothesis then takes the form of theory. A theory when repeatedly gives the same results after experimentation and gives correct explanation of the scientific facts becomes a law or principle.
 

A theory remains valid until contrary informations are given on the basis of experimentation. Thus a hypothesis requires experimental support. But Avogadro’s hypothesis has been accepted as law without any experimental support.

3. Prediction

Facts, theories and laws which are deduced from observation can help in deducing more facts and phenomenon. This process is called prediction.

4. Experiment

An experiment is an integrated activity, which is performed under suitable conditions with specially designed instruments to get the required information. Such information is used to test the validity of the hypothesis. If a hypothesis is proved correct. It increases the reliability of known facts. If it is proved wrong, it stil can give information which can be used to deduce other results.

CHEMISTRY AND SOCIETY

Chemistry has played important role for well being of mankind in the form of food, clothing, shelter, medical treatment and chemical fertilizers, crops protected by insecticides, refined food and production of artificial fiber. Production of cement, iron bricks, glass, paint etc are all due to chemistry.
The hazards of chemistry are so vast that no aspect of human life has remained unaffected. The smoke coming from chimneys of chemial industries and from vehicles pollute the air. It is very dangerous to breath in that air. Similarly waste water from industry, pollute canals, rivers and has bad effect on land. Excessive chemical spray on plants also has bad effect.

Radicals:
 

            Such elements and compounds having charge are called radicals. There are two types of radicals:
1. Negative radical
2. Positive radical

1.   Negative Radicals:
 Such elements and compounds having negative charge are called negative radicals.

No.	Radicals	Symbols
01	Chlorine  /  Chloride	Cl -1
02	Fluorine  / Fluoride	F -1
03	Bromine  /  Bromide	Br -1
04	Chlorate	ClO3-1
05	Peroxide	O -1
06	Oxide	O -2
07	Bi-carbonate	HCO3-1
08	Carbonate	CO3-2
09	Paramagnet	MnO4-1
10	Magnate	MnO4-2
11	Acetate	CH3COO-1
12	Sulphar  / Sulphid	S-2
13	Bi-sulphate	HSO4-1
14	Sulphate	SO4-2
15	Bi-sulphite	HSO3-1
16	Sulphite	SO3-2
17	Nitrogan  /  Nitride	N-3
18	Phosphate	PO4-3
19	Phosphite	PO3-3
20	Chromate	CrO4-2
21	Di-chromate	Cr2O7-2
22	Oxalate	C2O4-2
23	Hydride	H-1
24	Nitrate	NO3-1
25	Di-nitrate	NO2-1
26	Borate	B4O7-2
27	Silicate	SiO3-2
28	Phosphorous	P-3
29	Aluminate	AlO2-1
30	Format	CHOO-1
31	Cyanide	CNO-1

  

2.   Positive Radicals:
Such elements and compounds having positive charge are called positive radicals.

No.	Radicals	Symbols
01	Sodium	Na+1
02	Ammonium	NH4+1
03	Hydrogen	H+1
04	Rubidium	Rb+1
05	Potassium	K+1
06	Calcium	Ca+2
07	Barium	Ba+2
08	Nickel	Ni+2
09	Cobalt	Co+2
10	Magnesium	Mg+2
11	Manganese	Mn+2
12	Zinc	Zn+2
13	Copper  / Cuprous	Cu+1
14	Cupric	Cu+2
15	Boron	B+3
16	Bismuth	Bi+3
17	Antimony	Sb+3
18	Silver	Ag+1
19	Gold	Au+3
20	Ammonium	NH4+1
21	Cadmium	Cd+2
22	Carbon	C+4
23	Mercurous	Hg+1
24	Mercuric	Hg+2
25	Beryllium	Be+2
26	Starnium	Sr+2
27	Chromium	Cr+3
28	Ferrous	Fe+2
29	Ferric	Fe+3
30	Lithium	Li+1