Introduction to Chemistry

Introduction to Chemistry

(Chapter-1)

Chemistry
The branch of science which deals with the study of matter,its composition and structure, changes in matter and laws and principles which govern these changes.

Matter
Anything that has mass and occupies space is called matter.For example,gases,air and water etc.

Branches of Chemistry
Some main branches of chemistry are as follows:

1. Physical Chemistry: It deals with the fundamental principles underlying the various chemical phenomena.It is concerned with theories and experiments that describe the behaviour of chemicals

2. Inorganic Chemistry: It is study of all elements and their compounds except the hydrocarbons and their derivatives

3. Organic Chemistry: It is chemistry of hydrocarbons and their derivatives.

4. Analytical Chemistry: It deals with the detection and estimation of elements and compounds.It is concerned primarily with the composition of substances.

5. Industrial Chemistry: It is the branch of chemistry which is related to industrial processes.In other words,the study of properties,uses and their techniques of preparation of industrial products on large scale are studied in industrial chemitry.

6. Bio-Chemistry: It deals with the study of chemical changes that occur in living organisms.

7. Environmental Chemistry: It is the branch of chemistry which deals with the chemicals and other pollutants in the environment resulting directly and indirectly from human activities.

8. Nuclear Chemistry: Nuclear reactions are associated with radioactive substances.Such reactions are carried out in the nuclear reactors.The study of these nuclear changes,their effects and uses is called nuclear chemistry.

Some Basic Definations

1) Element
An element is the simplest form of matter which cannot be broken down into simpler form by chemical means.

2) Compound 
A compound is a substance which is obtained by the chemical combination of two or more elements in a definite ratio by mass.It may decompose into the components from which it is formed.

3) Mixture
A material obtained by mixing two or more elements or compounds in any ratio so that the properties of the elements or the compounds forming the mixture do not change at all is called mixture.

Substance:
Any form of matter which is homogeneous and cannot be separated by mechanical methods is called a substance.For example,carbon,water and alcohol is a pure substance.

Classification of Elements

(i) Metal:
Metals are usually solids with shining surfaces and are good conductors of heat and electricity at room temperature.

(ii) Non-metal:
The elements having dull surfaces and bad conductor of heat and electricity are called non-metals.

(iii) Metalloid:
The elements which have the properties of both metals as well as of non-metals are called metalloids.

Steps not 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
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.