Introduction to Chemistry

Trinitrotoluene is used as:

1. a preservative
2. a fertiliser
3. a fuel
4. an explosive

Answer

an explosive

Reason — Trinitrotoluene (T.N.T) is an explosive, which is a product of chemistry that contribute to national defence.

Which one of the following is a pesticide?

1. benzoic acid
2. aldrin
3. sugar
4. gun powder

Answer

aldrin

Reason — Pesticides are the chemicals used to kill pests which affect the yield of crops and fruits.
Example : Aldrin

Mortar is used as:

1. a plastic material
2. a building material
3. an insecticide
4. a medicine

Answer

a building material

Reason — Mortar is a mixture of cement, sand and water. It is used as building material in construction of buildings.

Urea is an important:

1. fuel
2. preservative
3. fertiliser
4. food item

Answer

fertiliser

Reason — Urea is an important fertiliser that will provide essential nutrients to crops and increase their yield.

The chemicals prescribed by a doctor in treatment of infectious diseases are called:

1. antigens
2. preservatives
3. antibiotics
4. fertilisers

Answer

antibiotics

Reason — The chemicals prescribed by a doctor in treatment of infectious diseases are called antibiotics.
Example : Penicillin, Tetracyclin etc.,

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

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

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

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

(e) Inert gases were discovered by ...............

Answer

(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.

Write "True" of "False" against the following statements and correct the false ones.

(a) Chemistry plays an important role in our national economy. ...............

(b) Antibiotics are used as preservatives. ...............

(c) D.D.T. is an important fertiliser. ...............

(d) Gunpowder is an insecticide. ...............

(e) Enzymes secreted by our body are chemicals. ...............

Answer

(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

Match the following words in column A with those in column B :

Answer

Match the following scientists in column A with their discoveries or contribution in column B :

Answer

Name the scientists who discovered the following:

(a) Atoms

(b) Oxygen

(c) Safety lamp

(d) Elements

Answer

(a) John Dalton

(b) Joseph Priestley

(c) Sir Humphry davy

(d) Antoine Lavoisier

Give two examples for each of the following substances:

(a) food preservatives

(b) fuels

(c) fungicides

(d) medicines

(e) building materials

(f) chemical war weapons

Answer

(a) Food preservatives:

1. Sodium metabisulphate
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

Answer the following in one or two sentences:

(a) What is science?

(b) What is chemistry?

(c) What is a fuel ?

(d) What is Philosopher's stone'?

Answer

(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.

Think and name six chemical products which you use daily.

Answer

Six chemical products in daily use are:

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

Name the chemicals which help in increasing food production.

Answer

Chemicals which help in increasing food production are:

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

Who is known as the 'Father of Chemistry'? Why?

Answer

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.

How is chemistry helpful in improving the health of human beings ?

Answer

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) What is alchemy ?

(b) What kind of experiments did Alchemists do?

(c) What is the main difference between alchemy and chemistry ?

Answer

(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 scientific and spiritual practice that aimed to turn metals into gold. In contrast, chemistry is based on experiments and observations.

What is the contribution of chemistry in the following fields ?

(a) Industry

(b) Clothing

(c) Cosmetics

(d) National Defence

(e) Medicines

Answer

(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.