1 Introduction to Chemistry

Learning Outcomes
The children will be able to:
discuss the importance of Chemistry in daily life and its role in different
industries and life processes;
list important applications of Chemistry in day to day life;
list some industrial applications of Chemistry;
discuss the bio-sketches of some great scientists and their works,
appreciate the patience, perseverance, sacrifices and ethical conduct of
scientists.

UNIT 1 -CHEMISTRY AND ITS IMPORTANCE

SCIENCE OF CHEMISTRY
3WCEDAOJ2F

The branch of science which deals with the study of materials

(substances), especially about their composition, methods of preparation,
properties and their reactions with other substances, is called chemistry.
From the materials we mean common substances around us, such
Medicines as air, water, stones, various kinds of plants
and animals. It includes natural compounds
such as rocksalt,marble, petroleum; metals
like gold, silver, copper, etc.;animal products
Cosmetics Colours like milk, cheese, butter, etc.; vegetable
products like wheat, maize, oil seeds, etc.
In materials, we can include man-made
products like cement, glass, steel, plastic,
CHEMISTRY bronze, nylon, etc.
Metals Electronics
In the study of a particular material,
the chemists perform experiments with
that material under various conditions. They
make very careful observations and finally
Electrical
Goods
Pigments make conclusions regarding the behaviour
Plastics of the material.
In this process, sometimes chemists
Fig. 1.1

9
 discover other useful materials, which go a long way in making
life comfortable.
human
IMPORTANCE OF CHEMISTRY
XYOLIR52G9

Chemistry is of such vital importance that practically there

human activity which is directly or indirectly not dependent on it IS no
For example, the book you are reading is made possible only
chemists found methods for the production of paper from wood.because
developed ink which does not spread on paper. They developed metals
which printing machine is made. Following are the broad fields in from
They
knowledge of chemistry is employed extensively. which
lal Agriculture : The food supply to any society entirely depends ox
agriculture. However, with the increase in population, the pressure on
land has increased for the production of more food.
DID YOU KNOW Chemistry has helped agriculture in the following ways :
The petroleum gas obtained ) t helped in the production of artificial fertilisers which increase
Guring the refining of food production.
petroleum is cooled and (ii) It helped in the production of better seeds.
compressed under vey high (i) It helped in producing chemicals which kill insects (insecticides)
pressure when it gets liquefied fungi (fungicides) and unwanted herbs (herbicides).
and is commonly called
liquefied petroleum gas (LPG). 6] Mineral prospecting : Man needs a variety of metals for making
tis fled in steel cylinders and various kinds of machines and structures. Chemistry helps us in the
is marketed as household fuel. extraction of metals from their ores.
Similarly, petroleum is mined from underground reservoirs. Chemistry
shows the way of obtaining useful products from petroleum, such as petrol,
kerosene oil, diesel oil, wax, fuel oil, and petroleum gas.
Ac) Industry : Knowledge of chemistry helps us to make useful
SPOTLIGHT materials. For example, steel is the backbone of any industrialised
The alloys have far country. Similarly, by mixing two or more molten metals in certain fixed
Superior properties proportions we can prepare alloys. Chemistry tells us how to manufacture
than metals. For cement, which is a very essential material in building industries and
exarnple, duralumin is homes.
an alloy of aluminium,
Copper, magnesium (d) Medicine : Chemistry has helped us in discovering new drugs
and manganese which to fight diseases. Drugs like penicillin, tetracycline and ampicillin fight
is very light, yet as a variety of diseases caused by bacteria.
tough as steel. It is ler Consumer products : There was a time when most of the
used for making aircraft furniture and household articles were made from wood. However, due
frames. Similarly, we to fast dwindling forest reserves, the wood is being
can have alloys which replaced by plastic.
resist corrosion, such Plastic is such a versatile material that we can
as stainless steel. practically make
anything and everything from it. Similarly, cotton is being replaced by
man-made fibres such as rayon, nylon and terylene.
10
 forest wealth, which
Thus, chemistry is helping in the conservation of Furthermore, it is
ecosystem.
DID YOU KNOW ? IS very essential for the balance of the
providing man with cheap and durable substitutes.
Comman salt, sugar, vinegar preservatives which
and citric acid are
common (f) Household : Chemistry has provided food
used for feeding millions
household preservatives. prevent wastage of food. Thus, the food saved is
utensils have been
Similarly, sodium meta of hungry people. In kitchen, brass and aluminium
(LPG] is used
bisulphite and sodium benzonate
food
replaced by stainless steel. The liquefied petroleum gas
are powerful artificial for cooking.
preservative. polishes,
Ag) Cosmetic industry : All kinds of powders, creams, nail
of
lipsticks, cleansing lotions, Soaps, detergents, etc., are the result
us
research done by the chemists. It is this research, which has helped
to live in a clean environment.
DID YOU KNOW ? h] Protecting materials from corrosion : Paints, varnishes, greases,
effects of
Good laboratory apparatus etc., protect a large number of articles of daily use from the
moist air which causes corrosion.
is made from a special kind
of glass, called pyrex glass or Furthermore, chemistry has helped us to develop artificial dyes,
borosil glass. This glass expands
which are widely used in making paints and for printing purp05es.
very little on heating and does i) Electronics: Research in chemistry has provided versatile
not crack. Furthermore, it is
resistant to chemicals and materials such as silicon and germanium, which are widely used in
is transparent to see what making diodes. It is the diode which makes electrical circuits in radios,
happens during a chemical televisions, computers, calculators, etc.
reaction.
(j) Space research : The present day space technology is the direct
result of production of better and more powerful fuels. It is the discovery
of these fuels which has helped us to launch space satellites.
Thus, to sum up, we can say that chemistry helps the mankind to
shape its own destiny by modifying materials available in nature, or by
synthesising materials, which are not available in nature.
Some common chemistry laboratory apparatus.
AH2DJQLOY7

Some common chemistry laboratory equipments are shown in

Figs. 1.2 la) to 1.2 (t).
(a) Test tube
ta] Test tube : Fig. 1.2 (a). Test tubes are of various sizes and are
made from different types of glass. A test tube which is heated directly
(b) Test tube holder
on flame is made from pyrex glass and is commonly called hard glass
test tube or boiling test tube.

bf Test tube holder:Fig. 1.2 (b). It is a kind of an iron tong provided

with wooden or plastic handle. It is used for holding a test tube when a
substance is being heated.
Uc Test tube stand or Test tube rack :Fig. 1.2 lc). It is a plastic or
(c) Test tube stand or wooden stand for keeping test tubes in vertical position.
Test tube rack

11
 ld) Round bottomed flask : Fig. 1.22((d). It is a glass
a spherical bulb and a narrow cylindrical neck. It is
heating liquids.
container
generally used with
for
le) Flat bottomed flask : Fig. 1.2 le). It is a glass container with
a spherical bulb, which is flattened at the base and is provided
() Round bottomed cylindrical neck. It is used for the mixing/storing chemicals in the with
fiask
of liquids. form
fe) Flat bottomed flgsk

(f) Conical flask : Fig. 1.2 (f). It is a cone shaped flask with aflat
s h r

base and provided with a cylindrical neck. It is also Used for mixing|
storing chemicals in the form of liquids.

(g) Beaker : Fig. 1.2 (g). It is an open glass container, cylindrical

() Conical flask
shape and provided with a lip for pouring out liquids. The beakers ars
of different sizes such as 50 cc, 100 cc, 250 cc, 500 cc.
(9) Beaker

(h) Glass tubing : Fig. 1.2 (h). It is a hollow glass tube of3 mos
diameter and open at both ends.It is generally used for shaping deliveny
tubes of various shapes by heating.

(h) Glass tubing [i Glass rod : Fig. 1.2 li). It is a solid glass tube of 3 mm diameter
It is generally used for stirring chemicals in the form of liquids.
0 Glass rod GI Funnel: Fig. 1.2 ijl. It is dconical vessel provided with long tapering
neck and is made from glass or plastic. It iS employed for pouring out
liquids from one vessel to another without causing any spilling.
(k) China dish or Evaporating dish: Fig. 1.2 (k). It is made from
0) Funnel porcelain. It is used for evaporating chemicals in the form of solutions
by heating.
() China dish or
evaporating dish
MPipette : Fig. 1.2 (). It is a long narrow tube provided with a
nozzle at one end and a bulb in the middle. A circular mark is made
in its neck which signifies the volume of liquid which it can measure.
) Pipette
It is used for measuring a fixed volume of liquid chemicals and then
transferring it to another vessel.

Im) Burette : Fig. 1.2 (m). It is a long graduated tube provided with
a glass stopcock at its bottom end. It has a capacity of 50 ml. It is used
for pouring out a fixed volume of liquid (less than 50 m) chemicals.

(m) Burette In) Measuring cylinder or Graduated cylinder : Fig. 1.2 (n). It is a
cylindrical glass vessel provided with a flat base and a lip near the top.
(n) Measuring cylinder It is used for measuring a definite volume of a
or graduated cylinder liquid and then pouring
it out into another vessel.
12
 holding a glass apparatus
fo Ironstand : Fig. 1.2 (o). It is used for
round bottomed flask or hard glass test tube) in a specific
lgenerally
position.
hollow frame provided
Ap) Tripod stand : Fig. 1.2 (p). It is a triangularapparatus, which needs
with three legs, and is used for supporting glass
(o) Iron stand heating.
(p) Tripod stand
wire mesh provided
tqlAsbestos wire gauze : Fig. 1.2 lq). It is an iron
distributes heat from the
with a thin sheet of asbestos in the middle. It
cracking.
burner evenly to the glass apparatus and hence prevents its

(a) Asbestos wire gauze Art Mortar and pestle : Fig. 1.2 (r). It is made from glazed porcelain.
hammered
The solid substances are placed in mortar and then gently
with pestle so as to powder them.

(r) Mortar and pestle

s Spirit lamp : Fig. 1.2 (s). It is a flat cylindrical vessel made of
glass or brass and provided with a brass neck through which passes a
thick cotton wick. It is filled with methylated spirit. On ignition the spirit
burns to produce very hot flame, which is used for heating chemicals.

(t) Bunsen burner :Fig. 1.2 (t). Modern chemistry laboratories use
Bunsen burner, in place of spirit lamp, for heating purp0ses.
(s) Spirit lamp
() Bunsen burner
When the Bunsen burner is connected to the gas supply, the gas
Fig. 1.2 : (a) to (t) issues out of the nozzle with a good pressure and in doing so, sucks
in the air from the air holes. This mixture of gas and air when ignited
burns on the top of burner tube with blue flame.
Exercise 1.1
A. Fill in the blank spaces by choosing the correct words from the list given below :
3
List :metals, fertilisers, cement, reservoirs, pestle, hard, pipette, roünd, rod
(1) Artificial have helped farmers to grow more food.
2. Petroleum is mined from underground
3. is a very essential material for building industry.
Paints protect from corrosion.

5. Aboiling tube is also called a qlass test tube.

6. Solid substances are ground with the help of a in a mortar.
6, 0
(7) A is used to measure a fixed quantity of a liquid.
3, 2
8. A bottomed flask is used for heating liquids.
9.) Aglass is used for stirring liquids.

13
 correct statements :
B. Statements given below are incorrect. Write
1. Herbicides are used to kill plant insects
methods.x
. Powders, creams and other
cosmetics cannot be made by chemical
3. Aconical flask is used to heat liquids.x
4. By mixing two or more metals we can
prepare an alloy.

C. Match the statements:

1. Used to increase fertility of soil. la) Alloy
superior material made by mixing two or more molten
A
metals. b) Food preservative
3. Used for killing unwanted herbs. lc) Fertilisers
4. Used in stopping the wastage of food. ald) Herbicide
5. Serves as support for heating glass apparatus. (6)lel Funnel
spilling. Sl Tripod stand
6 Used for transferring liquids from one vessel to another without
D. Write 'true' or 'false':
1. Economic strength of a country depends upon the quality of its chemists.
2. Chemistry has solved most of the problems facing mankind.
3. Fertilisers increase food production.
4. Plastic is a good substitute of wood.
5. Diodes are used in improved fuels.
6. CFC is used in refrigerators as a coolant.
E. Tick W
the most appropriate answer.
1. Chemistry is a branch of science that deals with:
lal production of better seeds (b) mineral prospecting
Wet study of composition of substances (d) study of plants
2. An apparatus used to spread heat evenly, under aglass apparatus is:
lal tripod stand (b) iron stand det wire gauze (d) Bunsen burner
3. An apparatus used for measuring a small and fixed volume of a liquid is :
la) burette tot pipette lc) measuring cylinder (d) conical flask
F. Find the odd one out. Give a reason for your answer.
1. pesticide, insecticide, mango seed and fertiliser.
round bottomed flask, iron stand, pipette and measuring cylinder.
cotton, jute, silk and nylon.
petrol, diesel, coal and kerosene oil.
G. Answer the following questions:
1. Define chenistry.
2. How is chemistry useful in agriculture?
3. How does chemistry help us in the preservation of food?
4. Name a few consumer products made by chemists. How are these products useful to us?
5. How does chemistry help in the development of space research and electronics?
6. Why is a boiling tube made from special glass?
7, Why is a wire gauze placed under glasS apparatus, when heated?

14
 CHEMISTRY
UNIT 2 - DEVELOPMENT OF
HISTORICAL
DEVELOPMENT OF CHEMISTRY--A 18OPU2AFGL
PERSPECTIVE
be explained by scientific reason.
Magic is something which cannotwere wizards who could call spirits.
Earlier people thought that alchemists
by using some strange words
The alchemists wanted to fool the people gold.
ike "Hocus pocus" to convert a base metal into
Ancient Greek word"Khumeria
The word "Alchemy"" oriqinated from
DID YOU KNOW? Which is an ancient branch of natural philosophy.
considered to be early
Base metal is a cheaper The people who are practising alchemy were attempted
metal than gold or silver. For chemists and were known as ""Alchemists". Alchemists were
example, zinc, iron, lead, tin, to purify, mature and perfect certain materials.
etc., are base metals.
which is now
In India, Alchemy was also practised for medicines
known as Ayurvedic medicines.

DID YOU KNOW ? In the 16th century the alchemist Paracelsus promoted the
experimental aspects over the spiritual ones. In 17th century Glauber
Glauber heated common salt discovered sodium sulphate, which was named after him and called
with oil of vitriol (sulphuric Glauber's salt. He also prepared hydrochloric acid. Chinese alchemists
acid) in a glass flask and discovered gun powder in 9th century by mixing powdered charcoal,
obtained sodium sulphate (a sulphur and nitre in certain fixed proportion. Gun powder is used in fire
salt known by his name) and
hydrochloric acid gas. This gas works. In 8th century alchemist Jabir Ibn extracted some compounds
on dissolving in water formed from herbs which were used as general anaesthesia during operations
hydrochloric acid. on humans.

FOOD AND CHEMISTRY

DID YOU KNOW? KUH68w9Ci1

When alcohol is treated with Food science deals with the production, processing. preparation
organic acids such as acetic and utilisation of food. Food chemists work with plants that have been
acid, propanoic acid, it forms harvested for food. They also work with animals which are useful to
a compound which have a humans. Chemistry helps in the production of safe and healthy food in
fruity smell. These compounds the following ways.
are commonly called esters.
" Animal Chemists
Animal chemists conduct research on animals which are useful
to humans.
Flavour Chemists
Flavour chemists use knowledge of the chemistry of food ingredients
and create new and improved flavours.
" Food Chemists
Food chemists help in processing. packaging. preserving. storing
and distributing foods and drinks to make them safe.
15
 Nutritional Chemists
SPOTLIGHT Nutritional Chemists perform research on tthe physical and
The iron pillar near Qutub
Minar was made around
properties of nutrients.
chemical
1215 AD. It is a marvel " Soil and Plant Chemists
of Indian metallurgY Soil and Plant Chemists examine the composition of soil and its
methods to
achieved by the Indian effects on plant growth and develop
conserve
manage the fertility of soil. They help farmers by
providing themand
metal workers. It is 8 m
tall and weighs 6 tonnes pesticides.
with agro-chemicals like fertilisers,
This pillar has not rusted
in the last 16 centuries. fungicides.
insecticides and
COSMETICS AND CHEMISTRY
UHO5JYOCAT

Cosmetics are an excellent example of how discoveries in

of
part of our dayto day lives. Al kinds powders, creams, lipsticks,
chemistry are
lotions, deodorants, nail polishes, soaps, detergents, etc., are
chemists.
,cCOSmet
leansinigcs.
These are the result of research done by the
Cosmetics are chemical compounds which are used to improve
our
said that
It is likely because of the appearance. It is not a recent phenomenon. It is the
formation of a thin film
queen bathed in milk, as a way to keep her skin beautiful and soft
Egyptian
of magnetic oxide of iron
(Fe,0,] on its surface, as The different cosmetic products have a strong component of scientific
a resuit of the finishing innovation, developed in modern research laboratories. For example,
treatment given to the Talcum powder is made up of magnesium carbonate and zinc oxide
pillar, by painting it with
a mixture of different
salts, then heating and CLOTHING AND CHEMISTRY
quenching in water. 1WCNTPELMG

Polymer chemistry has contributed to clothing technology by providing

man-made or synthetic fibres to replace natural polymers such as silk,
cotton, wool, etc.
Types of man-made (synthetic) fibre
i) Rayon or Artificial silk : The raw material for the production
of rayon is pure cotton or wood cellulose. Rayon is sometimes
called regenerated fibre, because it is produced by modifying
the natural fibre. It is not a truly artificial fibre, because its raw
material is natural fibre. However, for all practical purposes it
Fig. 1.3 : Rayon fabric
is included into man-made fibre or synthetic fibre. The filament
of rayon can be woven like any other natural fibres. They have
a feel and texture of natural silk.
lül Nylon: lIt is a superior type of synthetic fibre, which is truly
artificial. The nylon fibres are elastic, strong and water resistant.
It is used for making fabric for clothing and parachutes. It is
used for making stockings, ropes for rock climbing and fishing
Fig. 1.4 : Nylon articles
nets. It is used for making common household articles such
16
 zip-fasteners, hooks, etc. Tyre cords,
as tooth brushes, combs, washers, pulleys, etc., are
small parts of machines, such as
made from nylon fibres.
drawn into very fine filaments so
() Polyesters: The polyester can be a number of varieties of esters.
as to form artificial fibre. There are
filament is similar, but
Terylene filament is one of them. This
used for making fabrics
Superior in properties than nylon. It is largely materials. Terylene
for shirts, trousers, sarees and other dress conveyor
hoses and
is used for making sails for sailing boats, fire
belts.

Fig. 1.5: Polyester dresses Advantages of Synthetic Fibres

1. They can be easily washed. 2. They get dried quickly.
3. They do not get creased. 4. They are cheaper.

CHEMICALS AS MEDICINE
F4RLA8D5N1

Man has been dependent on medicinal plants right from the dawn
of civilisation. He used leaves, roots, seeds or fruits of medicinal plant
to cure himself from common diseases. However, these days chemists
have developed methods to identify the active molecules in a medicinal
plant. Thus, by extracting these molecules from plants, better medicines
are prepared. Chemists have also developed methods to prepare such
molecules artificially, thereby reducing dependence on medicinal plants.
Even new molecules with better properties have been made in laboratory.
which has helped to cure a number of incurable diseases. Discovery of
Fig. 1.6: Some common
medicines
penicillin, tetramycine, sulphadiazine, etc., are the examples of new
medicines developed by the man. Quinine is an example of medicine
extracted from the bark of a cinchona plant.
Chemistry plays a huge role in the development of synthetic drugs
such as antibiotics, antimalarials and analgesics (pain killers). New
research is being done on possible ways so that chemistry can be used
to target cancer cells without killing the healthy cells around the cancer
growth.

CHEMICALS IN INDUSTRIES
AD2VMS6O0Q
Industries are set up to produce a large number of consumer products.
Chemistry has helped in the growth of different industries. Chemicals
used in industry to process the raw materials so as to improve their
properties are called industrial chemicals. They are used in removing
stains.
Stain removal: Stain removal is the process of removing a spot left
17
 A solvent or
by one substance on a fabric. detergent is generally
to remove the stain. On ironing the
fabric having stain, it
gets used
bonded to fabric. So ironing of the stain should be avoided chemically
) Household bleach contains hydrogen peroxide
Powerfut Stsln Removal Products to Keep Handy used to remove common stains.
which can be
[il Sodium hydrosulphite and sodium hypochlorite are
used for removing stains and dye colours. normally
(iil Acetone is good for removing some glues, nail polish, ink
rubber and grease. Nail polish remover also Contains stains,
Dtoinb t e

iv Detergents are used for washing clothes and acetone.

Fig. 1.7 : Some common
stain remover
oil spots, etc. removing stains,
[v) Lemon juice contain citric acid and acts as bleaching
stains. Its action can be accelerated by agent.
It
can remove
exposing
the stain to sunlight. Boric acid, vinegar lacetic acid) are used
to remove stains caused by rust.
(vi) Sodium hydroxide is also commonly used in drain cleanere
It allows grease and other oils to dissolve in water. Potassium
hydroxide is another alkali which is also used in this regard.
(vi) Glycerine can be used to soften "set" stains, especially on wool
and non-water-washable fabrics.
[vii) Boiling water can be used to take out fruit juice stains.
DARK SIDE OF CHEMISTRY

No doubt knowledge of chemistry helps us to produce certain

chemicals which are very useful in maintaining health services, in the
production of food or for national defence. However, the misuse of such
chemical bring about massive destruction. Some examples are as follows:
1. Chemical weapons: Chemistry has helped to produce deadly
explosives such as tri-nitro-toluene (T.N.T.), tri-nitro-glycerine
(TN.G) and Rapid denonating explosive (RDX), which are used as
main ammunition for army. However, the same explosives in the
hand of terrorists bring about lot of misery.
2. Pollutants: Chemicals such as BHC (benzine hexachloride) and DPT
(dichloro-diphenyl trichloro ethane) are widely used in controlling
mosquitoes. However, these chemical pollute air, water and soil.
They enter in food chain and cause serious diseases in human
beings.
Fig. 1.8: Chemical weapons
3. Addictive drugs: Drugs like, cocaine, morphine, heroin, etc., are
useful in removing anxiety or pain under very strict medical con
trol. However, same drugs without medical control became addic
tive and can kill a person, if someone takes overdose by mistake.
18
 CONTRIBUTIONS
NOTABLE PERSONS AND THEIR
RWE794DKF8

1. Henry Cavendish (1731-1810) 1731.

Cavendish was born in Nice, France, on October 10,
Henry
hydrogen gas and the composition of water contains
He discovered oxygen by volume. He prepared
two parts of hydrogen and one part ofaction of dilute acids on metals.
inflammable air" (hydrogen) by the
fermentation, a chemical reaction
He also investigated the products of
into simple substances. He
that splits complex organic compounds carbonate and
discovered the reversible reaction between calcium
causes temporary
carbon dioxide to form calcium bicarbonate, which
such water by
hardness of water. He also found out how to soften
Henry Cavendish adding lime (calcium hydroxide).
2. Antoine Lavoisier (1743-1794)
Antoine Lavoisier was born in Paris (France) on August 26, 1743.
Antoine Lavoisier revolutionised chemistry. He named the elements
carbon, hydrogen and oxygen. He discovered oxygen's role in
combustion and respiration. He also established that water is a
Compound of hydrogen and oxygen; and he discovered that sulphur
is an element.
He gave the Law of Conservation of Mass.
He made a clear difference between elements and compounds. He
made a list of chemical elements which included oxygen, nitrogen,
hydrogen, sulphur, phosphorus, carbon, antimony, cobalt, copper, gold,
Antoine Lavoisier
iron, manganese, molybdenum, nickel, platinum, silver, tin, tungsten,
and zinc.

3. Dmitri Mendeleev (1834-1907)

Dmitrilvanovich Mendeleev was born on February 8, 1834 in Verkhnie
Aremzyani, in the Russian province of Siberia.
In 1860, Mendeleev attended the first International Chemistry
Conference, which took place in Germany. Mendeleev's periodic table
was based on atomic weights.
He wrote the name of the 65 known elements on cards-one element
on each card. Then he wrote the properties of each element on the
card. He found that the properties of the elements get repeated with
the increase in atomic weight. He arranged the elements in increasing
Dmitri Mendeleev order of their atomic weight in the form of a table which he called
Periodic Table.
He proposed that atomic weight of some elements were wrongly
measured. It was later found to be correct. Also he predicted the
19
 existence of eight new elements and their properties. Later on these
elements were discovered. In his honour an element which Wo
discovered later was named as Mendelevium.

4. Robert Boyle (1627-1691)

Famous as Being the first "Modern Chemist". He is als0 known
"Father of Modern Chemistry".
He was born in Ireland. In 1654, after moving to Oxford he workod
on gases using an air pump made by Robert Hooke. He proved that
sound does not travel in a vacuum. In 1662, he discovered Bovle's
Robèrt Boyle Law. He worked on flame tests and acid-base indicators in chemistny
He defined elements, compounds and mixtures.
5. John Dalton (1766-1844)
Famous for ldentification and presenting the atomic theory. He Was
aBritish chemist and physicist. But he is the best recognised for his
work on the Atomic Theory and research on colour blindness. He
successfully identified chemical compounds and reactions affected
John Dalton
by interaction of atoms with one another.
Exercise 1.2
the list given below:
A. Fill in the blank spaces by choosing the correct words from
List : Clothing, reason, innovation, Rayon, Glauber's
1. Magic is something which cannot be explained by scientific
2. Sodium sulphate is also known as salt.

3. The different cosmetic products have a strong component of scientific

4. Polymer chemistry has contributed to technology.
5. is sometimes called regenerated fibre.
B. Statements given below are incorrect. Write correct statements :
1. Flavour chemists use knowledge of the chemistry of fragrance and create new and improved perfume for
mankind.

2. Detergents are used to remove stains caused by rust.

3. Nylon has a feel and texture of natural silk.
4. Rayons are compounds formed, when alcohol is made to react with organic acids.
5. Quinine is an example of medicine made from the animals product.
C. Match the statements:
1. Something which cannot be explained by scientific reason. la) John Dalton
2. A person which has contributed to the study of processing of food. (b) Rayon
3. The fibre known as regenerated fibre. (c) Magic
4. A branch of chemistry which has also contributed to clothing technology. (d) Polymer chemistry
5. Achemist who is the best recognised for his work on the Atomic
Theory and research on colour blindness. le) Food chemist
20
D. Write 'true' or 'false' for the followingstatements :
1. Food chemists work with plants that have been harvested for food and animats
which are useful to humans.
2. Man has been independent on medicinal plants in ancient time.
3. A solvent or detergent is generally used to remove stain.

4. Forensic scientists work for Finance Department for giving proper advice regarding
economic policy.
5. Henry Cavendish discovered hydrogen and composition of water.
E. Tick () the most appropriate answer.
1. Which ofthe following chemical compounds is used to improve our appearance?
(a) Medicines (b) Cosmetics (c) Adhesives (d) All of these
2. Which of the following artificial fibres is known as artificial silk?
la) Rayon (b) Nylon (cl Polyester (d) Acrylon
3. The analgesic drug is generally known as
lal antibiotic (b) paracetamol lc) pain killer (d) antimalarial

4. Which of the following chemists discovered oxygen's role in combustion and respiration?
la) Henry Cavendish (b) Antoine Lavoisier (c) Dmitri Mendeleev (d) Robert Boyle
5. Which of the following chemists recognised for his work in atomic theory and research on colour bindness?
la) John Dalton (b) Robert Boyle lc) Henry Cavendish (d) AntoineLavoisier
F. Answer the following questions:
1. Write short notes on development of chemistry-a historical perspective.
2. How does chemistry help in the production of food?
3. How can you say chemistry plays a vital role in the production of cosmetics?
4. (a) Define polymer chemistry.
(b) Write at least three synthetic fibres and explain their properties and uses.
5. How does chemistry help in medical applications? Explain properly.
6. (a) Define industrial chemistry.
(b) What do you mean by stain removal? Write at least three stain removers and their proper applications
in removing the stain.
7. List at least three notable persons and mention their contribution to chemistry.

KEYWORDS
1. Chemistry The branch of science which deals with the study of materials (substancesl; especially
about their composition, methods of preparation, properties and their reactions with
other substances.
2. Food Science
: Ascience which deals with the production, processing. preparation and utilisation of
food.
3. Cosmetics
: The chemical compounds which are used to improve our appearance and also help
us to live in a clean environment.
4. Polymer : The chemistry which has contributed to clothing technology by providing man-made to
Chemistry replace natural polymers such as silk, cotton, wool, etc. Rayon, nylon and polyester are
examples of some man-made fibres.
21
 :A branch of chemistry, which has contributed to prepare the useful products from raw
5. Industrial
Chemistry materials by using some physical and chemical processes.
substances on a fabrics.
6. Stain Removal: Aprocess of removing a spot left by some
HIGHLIGHTS IN REVIEW
1. The branch of science which deals with the study of materials, especially about their composition,
chemistny
methods of preparation, properties and their reactions with other substances is called
stones soil t
2. From materials we mean, common substances around us such as, air, water, trees,
activities.
3. Chemistry plays a very important role in all kinds of human
4. A solvent or detergent is generally used to remove the stain.
5. Henry Cavendish discovered hydrogen and the composition of water.
6. Antoine Lavoisier revolutionised chemistry. He named the elements carbon, hydrogen and oxygen,. He
discoveredoxygen's role in combustion and respiration and sulphur as an element. He also established
that water is a compound of hydrogen and oxygen.
7. Dmitri Mendeleev formed a periodic table which was based on atomic weights, He proposed that atomic
weight of some elements were wrongly measured. It was latter found to be correct. Also he predicted
the existence of eight new elements and their properties.
8. Robert Boyle proved that sound does not travel in vacuum. He discovered Boyle 's law. He worked on
flame test and acid-base indicator.
9. John Dalton is the best recognised for his work on the atomic theory and research on colour blindness.

THEME ASSIGNMENTS
A Fill in the blank spaces:
l Chemistry has led us to develop which in turn help in conserving forests Irubber/plastics)
lül Artificial have helped farmers to grow more food. (fertilisers/fungicidesl
lil Cosmetics are compounds which are used to improve our appearance. lphysical/chemical)
B. Write true or false for the following statements.
1 Herbicides kills insects.
li) Terylene is a man-made product.
lil All kinds of cosmetics are the result of research in chemistry.
C. Tick / the most appropriate answer :
) What is the backbone of an Industrialised country?
lal Plastic (b) Fertilisers (c) Cotton (d) Steel
(ii) LPG is :
lal Liquefied Petrol Gas (b) Liquid Petrol Gas
lc) Liquefied Petroleum Gas (d) Liquid Petroleum Gas
(ii) Which monument was made around 1215 AD?
lal Qutub Minar (b) Taj Mahal (c) Hawa Mahal (d) Amer Fort
fiv) Rayon is produced from :
la) cotton (b) silk (c) paper (d) wool
(v) Which chemical is used to remove glues?
lal NaOH (b) Glycerine lc) Fe,0, (d) Acetone

22
D. Statements given below are incorrect. Write the correct statements.
() Pesticides fight variety of diseases caused by bacteria.
(ü) Nylon is an improved natural product.
ii) Rayon is water proof as well as air proof.
E. Assertion-Reason Type Questions
Reason lR). Read the
In the questions given below, there are two statements marked as Assertion (A) and
statements and choose the correct option.
la) If both Assertion (A) and Reason (RI are correct and Reason (R) is the correct explanation of
Assertion (A).
(b) I both Assertion (A) and Reason (R) are correct but Reason (R) is Not the correct explanation of
Assertion (A).
(c) If Assertion (A) is true but Reason (R) is false.
(d) If Assertion (A) is false but Reason (R) is true.
i) Assertion (A) : Moist air corrodes iron.
Reason (RJ: Rusting happens in the presence of moisture.
li) Assertion (A) : Polysters are hard materials.
Reason (RJ: Polysters are used to form artificial fibre.
(ii) Assertion (A] : Tyre cord is made up of nylon.
Reason (R): Combs are made from nylon.
F. Case Study Based Questions
Read the given information carefully and answer the questions that follow:
There are many industries which use chemicals to improve the properties of the product. These chemicals
are used with raw materials. Many chemicals are used for removing stains, to dye clothes etc. Chemistry
has helped in the growth of different industries.
i) Which acid is used to remove stain caused by rust?
la) Acetic acid (b) Oxalic acid (c) Citric acid (d) Both lal and (c)
(i) Nail Polish remover contains
(a) acetone (b) NaOH (c) potassium hydroxide (d) none of these
(ii) Dyes, colours are removed with:
la) hydrogen peroxide (b) sodium hydrosulphite (c] sodium hypochlorite (d) both (b) and (c)
G. Answer the following questions:
1. (a) Name twO medicines which fight bacterial diseases.
(b) Name two man-made products used for making dresses.
2. What do you mean by cosmetics? How does chemistry become helpful in this regard?
3. (a) Write short note on polymer chemistry.
(b) Write three synthetic fibres and explain their properties and uses.
4. List at least three notable persons and their contributions to chemistry. Explain briefly.
H. Problem-Solving Skill Based Question
There are many medicines which are not good for health and have many side effects but doctors still refer those
medicines. This type of activity is seen in hospitals also. What steps you will take to stop this activity?
I. Art-Integration Based Question
(i) Draw the different articles used in chemistry laboratory on chart paper.
J. Inquiry Based Questions
(i) Inquire about the chemicals used in manufacturing of soaps and detergents.
(i) How is nail polish harmful for nails?

To get the Worksheet of this chapter scan this QR Code

D
CoDE-GGH%

23