1.1. GENERAL INTRODUCTION: Science is considered as a continuous human effort to systematise knowledge to describe and understand nature.It is such a wide subject that for the sake of convenience,it is subdivided into different disciplines which mainlyinclude chemistry,physics,biology, etc.
CHEMISTRY: Chemistry is the science of molecules and their transformations.It is the science not so much of the one hundred elements but of the infinite variety of molecules that may be built from them.
[chemistry is the branch of science which deals with the study of composition,structure and properties of matter and the changes which the matter undergoes under different conditions and the laws which govern these changes].
MATTER: anything which has mass and occupies space is called matter.
Everything around us, for example, book,pen,pencil,water,air, all living beings etc. are composed of matter* in these three states can be represented as shown in fig.1.1.
FIG. 1.1 Arrangement of particles in solid,liquid, and gaseous State
In solids, these particles are held very close to each other in an orderly fashion and there is not much freedom of movement.
In liquids, the particles are close to each other but they can move around.
In Gases, the particles are far apart as compared to those present in solid or liquid states and their movement is easy and fast.Beacause of such arrangements of particles, different states of matter exhibit the following characteristics:
>Solids have definite volume and definite shape.
>Liquids have definite volume but not the definite shape. They take the shape of the container in which they are placed.
>Gases have neither definite volume nor definite shape. They completely occupy the container in which they are placed.
1.2. IMPORTANCE AND SCOPE OF CHEMISTRY:
chemistry plays an important role in our daily life. It has helped us to meet all our requirements for a better life such as food,good health, comforts etc. Without the knowledge of chemistry our life would have been very dull and dreary.
Some of the important applications of chemistry are given below:
1.SUPPLY OF FOOD.
with the increase of population,the need for the overall amount of food has increased manifold. Moreover, with increase in the standards of life, there has been increase in the quality and variety of food. Chemistry helped us to achieve these goals as follows:
(i) It has provided chemical fertilizers such as urea,calcium superphosphate, sodium nitrate, ammonium sulphate etc. which have increased the yield of fruits, vegetables and crops.
(ii) It has helped to protect the crops from insects and harmful bacteria by the use of certain effective insecticides,fungicides and pesticides.
(iii)The use of preservatives has helped to preserve food products like jam,butter, etc. for longer periods.
(iv) It has given the methods to test the presence of adulterants thereby ensuring the supply of pure food stuff.
2.CONTRIBUTION TO BETTER HEALTH AND SANITATION.
Chemistry has contributed towards better health and sanitation in a number of ways as follows:
(i)It has provided mankind with a large number of life saving drugs. In present days dysentery and pneumonia are curable due to the discovery of sulpha drugs and penicillin.
Similarly, life saving drugs like CIS-PLATIN and taxol have been found to be very effective for cancer therapy and AZT(Aziodothymidine)is used for AIDS victims. These compounds are obtained from animals and plants or by synthetic methods.
(ii)Analgesics have reduced pain of different types. Antibiotics(like chloromycetin, streptomycin etc.) have helped to curb infection and cure diseases like typhoid and tuberculosis.Transquilizers have helped to reduce tension and bring about calm and peace to patients suffering from mental diseases.
Antiseptics such as dettol are ysed to stop infection of the wounds. Disinfectants such as phenol are used to kill the microorganisms present in drains,toilets,floors etc. A low concentration of chlorine (0.2 to 0.4 ppm) is used for sterilization of water to make it fit for drinking purposes.
(iii)Discovery of anaesthetics has made surgical operations more and more successful.
(iv)the use of insecticides such as DDT and Gammexane has reduced the hazards of diseases caused by rats,mosquitoes and flies.
(v)New and more effective medicines are being discovered from time to time which are replacing the older less effective medicines. For example,quinine has been replaced by more effective antimalarials such as chloroquin,camoquin and primaquin.
(vi) Synthetic vitamins and tonics have contributed significantly towards better health.
In fact, the use of more effective medicines, vitamins etc. and better sanitary conditions have helped to increase the average life span.
3. SAVING THE ENVIRONMENT.
refrigerants like chlorofluorocarbons(CFCs)which destroy the ozone layer have been replaced by eco-friendly chemicals.However, Green house gases like CH4,CO2 etc. are still posing a challenge to chemists.
4.INCREASE IN COMFORTS,PLEASURE, AND LUXURIES.
Chemistry has placed a large number of utility goods at our disposal which have added to our comforts,pleasure and luxuries.Some of them are as follows:
(i)Synthetic fibres (cloth):In addition to the natural fibres like cotton,wool,silk, etc., chemistry has helped in the production of synthetic fibres such as terylene, nylon, rayon etc. which are more comfortable,durable and attractive. They are easy to wash, dry quickly and do not need ironing.
(ii)Building materials:Chemistry helped in supplying steel and cement, for the construction of safer homes and multi-storyed buildings and dams and bridges which can last for centuries.
(iii)Supply of metals:Metals like gold,silver,copper,iron,aluminium,zinc and a large number of their alloys are used for making ornaments,utensils,coins and many industrial and agricultural implements.
(iv)Articles of domestic use:Chemistry has made our homes more comfortableby supplying a large number of articles of domestic use such as detergents, oils and fats, sugar, paper, glass, unbreakable plastic wires, paints, varnishes, cosmetics, perfumes, cooking gas etc.
By the use of refrigerants like ammonia,liquid sulphur dioxide and freon, we can make our homes cooler in summer.
(v)Entertainment:Cinema, one of the common sources of entertainment and also video-cameras as well as simple cameras make use of films which are made of celluloid(a chemical compound) and coated with suitable chemicals.
Similarly, fire-works which amuse us on festivals and marriages are chemical products.
Phonograph records used for listening music are made up of polyvinyl chloride, a chemical compound.
5.Transport and communication: All the means of transport including automobiles (scooter,cars,trucks,buses etc.) aeroplanes, helicopters, railways use either petrol or diesel(petroleum products)or coal which are all chemical products.
6.Nuclear or Atomic energy: Chemistry providing us an alternate source of energy which is nuclear energy.A chemical process for the production of the compound, uranium hexafluoride,made possible the enrichment of U-235 which was used first for making atomic bomb and later in the nuclear reactor for production of electricity. Nuclear energy can also be used for digging tunnels, blasting mountains and in mining as well.
7. Application in industry:Chemistry plays an important and useful role in the development and growth of a number of industries, e.g., glass, cement, paper, textiles, dye, leather,paints,pigments,petroleum,sugar,plastics,pharmaceuticals etc.
Chemistry also helps in the production of sulphuric acid, nitric acid, ammonia etc. by providing suitable catalysts.
8.Applications in war: Chemistry is responsible for the discovery of highly explosive substances such as TNT, nitroglycerine and dynamite, poisonous gases like mustard gas, lewisite and phosgene and many other deadly weapons such as atom bomb and hydrogen bomb.
>PROBLEMS CAUSED BY PROGRESS IN CHEMISTRY:
The progress in chemistry has also caused many problems.
(i)Nuclear energy is useful but disposal of nuclear waste poses a serious problem to humanity
(ii)Antibiotics helps in the elimination of infectious disease but their overuse is harmful.
(iii) Insecticides increased the food supply but they do a lot of harm to birds, fishes, and useful insects.
(iv)Use if polythene bags is posing a serious threat to sewerage system.
(v) Chemistry has given drugs like LSD, cocain, brown sugar etc. which are proving a curse to the society.
CONCLUSION: In the above description, we conclude that chemistry can be regarded as greatest benefactor of humanity, yet it can prove to be a blessing or a curse for humanity depends upon the uses to which it is put and how a relative balance is maintained between benefits and problems caused by progress in chemistry.