Introduction to Chemistry

an explosive

Reason — Trinitrotoluene (T.N.T.) is an explosive, which is a product of chemistry that contributes to national defence.
Preservatives are chemicals added to a variety of foods to protect them from microorganisms and prevent their decomposition. Fertilisers are chemicals which provide essential nutrients to crops and increase their yield. Fuels are substances which, on combustion, produce a large amount of heat energy that can be used.

aldrin

Reason — Pesticides are chemicals used to kill pests which affect the yield of crops and fruits. Aldrin is an example of a pesticide.
Benzoic acid is mainly used as a food preservative, not as a pesticide. Sugar is a food substance, not related to pest control. Gunpowder is an explosive, not a pesticide.

a building material

Reason — Mortar is a mixture of cement, sand and water. It is used as building material in construction of buildings.
Insecticides are chemicals used to kill insects. Medicine is used to treat any disease.

fertiliser

Reason — Urea is an important fertiliser. It provides essential nutrients to crops and increases their yield.
Preservatives are chemicals added to a variety of foods to protect them from microorganisms and prevent their decomposition. Fuels are substances which, on combustion, produce a large amount of heat energy that can be used. Urea is not a food item.

antibiotics

Reason — The chemicals prescribed by a doctor in treatment of infectious diseases are called antibiotics.
Example : Penicillin, Tetracyclin etc.,
Preservative are the chemicals added to a variety of foods to protect them from microorganisms and prevent their decomposition. Fertilisers are the chemicals which provide essential nutrients to crops and increase their yield. Antigens are substances that enter the body and are recognized as foreign by the immune system, thereby triggering an immune response.

(a) Chemistry deals with the study of matter and the changes it undergoes.

(b) Fertilisers help to increase the production of food.

(c) Food items like jams and pickles are protected by using preservatives.

(d) L.P.G. is used for cooking.

(e) Inert gases were discovered by William Ramsay.

(a) True

(b) False
Correct Statement — Antibiotics are used as medicines.

(c) False
Correct Statement — D.D.T. is an important insecticide.

(d) False
Correct Statement — Gunpowder is an explosive.

(e) True

(a) John Dalton

(b) Joseph Priestley

(c) Sir Humphry Davy

(d) Antoine Lavoisier

(a) Food preservatives:

1. Sodium metabisulphite
2. Ascorbic acid

(b) Fuels:

1. Petrol
2. Diesel

(c) Fungicides:

1. Bordeaux mixture
2. Sulphur

(d) Medicines:

1. Aspirin
2. Paracetamol

(e) Building materials:

1. Steel
2. Cement

(f) Chemical war weapons:

1. Trinitrotoluene
2. Gunpowder

(a) Science is the systematic, ongoing effort by human beings to study, understand and utilise nature for meaningful purposes. This understanding is slowly developed by careful observations and experiments.

(b) The branch of science that deals with the study of the composition and the physical and chemical properties of various forms of matter is called Chemistry.

(c) Fuels are substances which on combustion produce a large amount of heat energy that can be used for various purposes. Example: Cooking gas (LPG), petrol, diesel, etc.

(d) Philosopher's stone is a mythical and magical substance (not an actual stone but wax, liquid or powder). which on heating with a base metal iron or copper would turn into gold, the purest form of matter which would bring wealth, health and immortality.

Six chemical products in daily use are:

1. Shampoo
2. Toothpaste
3. Face cream
4. Soap
5. Salt
6. Perfume

Chemicals which help in increasing food production are:

1. Fertilisers
2. Pesticides
3. Insecticides
4. Fungicides

Antoine Lavoisier is known as the "Father of Chemistry". He was the first scientist to use experiments to study chemical reactions. He also helped give names to many elements and discovered the role of oxygen in respiration and combustion.

Extensive research by chemists has led to the discovery and production of a large number of medicinal drugs. These medicines are the chemical substances which help to cure and prevent diseases.
They help in fighting diseases by killing their germs, and thus increase the life span of human beings.
Examples: aspirin, paracetamol, antibiotics (like penicillin, tetracyclin), antiseptics, etc.

(a) The word "Alchemy" has its origin in a Greek word 'Khemeia' which means "art of transmuting metals". It was partly based on experimentations and partly on spiritual discipline.

(b) Alchemists were successful to some extent in developing processes to extract metals and make alloys. They were the first to isolate zinc and phosphorous. Alchemy has also contributed to an incredible number of future uses of chemicals, metals, ink, paints, cosmetics, medicines, porcelain, etc.

(c) Alchemy was both a scientific and spiritual practice and it lacked a common language and standardized scientific methods. Chemistry, on the other hand, is a systematic branch of science based on careful observations, experiments and standard scientific methods.

(a) Industry — Chemistry has helped in the growth of different industries and in improving the efficiency of industrial processes. Industries are set up to produce a large number of consumer products like dyes, drugs, paints, plastics, synthetic fibres, petrochemicals, pharmaceuticals, steel, alloys, etc.,

(b) Clothing — Chemistry is used in textile industry, which manufactures clothing. Cloth manufacturing involves conversion of fibres into fabrics. Fibres can be natural or synthetic. Natural fibres like cotton, silk, wool, are used to produce dress materials, sarees, bags. Synthetic fibers like nylon, spandex, polyester are used to make towels, bags, bedsheets, curtains, etc.

(c) Cosmetics — Cosmetics are products used to cleanse, protect and change the appearance of external parts of human bodies. Example: talcum powder, skincare creams, lipsticks, eyes and facial make up, deodorants, lotions, perfumes, soaps, bathing oil, etc.,

(d) National Defence — Substances like gunpowder, T.N.T. (trinitrotoluene), phosgene, chemical weapons, laughing gas, etc. are all products of chemistry which contribute to the national defence.

(e) Medicines — Extensive research by chemists has led to the discovery and production of a large number of medicinal drugs. These medicines are the chemical substances which help to cure and prevent diseases.
They help in fighting diseases by killing their germs, and thus increase the life span of human beings.
Examples: aspirin, paracetamol, antibiotics (like penicillin, tetracyclin), antiseptics, etc.