CHEMISTRY IN DAILY LIFE

WHAT WE HAVE LEARNT

$ Medicines, insecticides, textiles and food materials that we use

in daily life are chemical substances.

$ Cement is used for building purposes becauses it has the ability

to 'set' when mixed with water.

$ Natural rubber is the exudation from rubber plants.

$ Polymers are very large molecules formed by the combination of small molecules.

CHEMISTRY IN DAILY LIFE

We live in a world of matter. From the food that sustain our lives to various

objects that have built up our physical culture, everything is made up of matter.

The human body itself is a mixture of matter of differing types. The humans

who used materials obtained from nature for centuries, later made new

materials out of these to suit their needs. Now the humans have thousand of

materials for their use - both natural and human made. The ability that

humans acquired to make new materials from natural materials is the basis

of human progress. When the structure of the material world and the nature

of physical and chemical changes in them were studied, humans were able to

make new materials and to control their different properties. The development

of chemistry made this progress possible. The contribution of chemistry to

fields like, agriculture, industries, health care, food industry, habitat,

transport and research has been invaluable. Through chemical processes that

scientists develop chemistry comes up every day with answers to ever

increasing human needs.

Polymers

Cotton is the material used for the

manufacture of clothes for our daily use. Clothes

are made by weaving together thick strands that

are obtained by twisting together delicate fibres.

Different kinds of fibres are utilized for different

purposes.

$ Cotton

$ Coconut fibre

$ Jute

$ Silk

The hair of animals, paper, wood and

rubber also contain such fibres. The varied

properties of such fibres are due to the

polymers present in them. From very early

times, humans have been using many polymers

that are obtained from plants and animals. In

modern times, we have been able to make

substances that are similar, and with better

qualities with the help of chemistry.

Some natural and human made polymers

that are used in daily life are given below.

Human-made Natural

$ plastic rubber

$ polythene cellulose

$ nylon starch

$ rayon silk

$ teflon wool

Table 5.1

Chapter 05

60 Chemistry

The protein known as insulin is a small

polymer formed by joining about fifty amino acid

units. In big polymers, hundreds of different units

may be joined in different ways. The form,

hardness, strength, heat-enduring capacity and

elasticity of a polymer can be changed by

incorporating alterations in the constituents of the

polymer and in the way in which these units are

connected. For example, by heating natural

rubber with sulphur, we get a stronger form of

rubber. This happens when the polymers

contained in natural rubber become new

polymers with the addition of sulphur.

In the manufacture of polymers, monomers

are allowed to undergo chemical reactions and

get united to each other.

Chemical equations showing the formation

of some polymer molecules are given below.

n CH2 = CH2 → [ CH2 - CH2 ] n

ethylene polyethylene

n CH2 = CH [ CH2 - CH ] n

| |

Cl Cl

Vinyl chloride Polyvinyl chloride (PVC)

Here, monomers combine and form

polymers. The polymer is named by prefixing

the word 'poly' to the name of the monomer unit.

Eg : polyethylene, PVC.

There is only one kind of monomer

molecules. Polyethylene, PVC, rubber etc.

are formed by same type of monomers.

They are formed by different types of

molecules.

Living polymer factories

We have started making polymers since

only the last two years. But for

centuries we are familiar with two

living beings who make and use

polymers, the spider and the silk worm.

The web of a spider and the silk fibre of

a silk worm have always aroused the

curiosity of humans. Both are

polymers. In 1665, a scientist, Robert

Hook, declared that if certain suitable

gum-like substances are drawn out as

thin fibres, substances similar to spiderweb

and silk fibre can be made. This

method is still used to in the industrial

production of polymers.

Rubber

Rubber is a naturally available elastic

polymer. There are double bonds in its

polymer molecules. To change the properties

of rubber, changes are to be made in the

structure of its polymer.

If sulphur is added to rubber and heated,

its shape can be maintained and its hardness

increased. The process of heating rubber with

sulphur for the betterment of its properties, is

called vulcanisation. In this process, the

various chains in rubber are joined using

sulphur.

Vulcanisation enhances the following

properties of rubber.

$ tensile strength

$ hardness

$ elasticity

$ ability to withstand heat changes

Chemistry in daily life

Standard 10 61

These properties can be varied by

changing the quantity of sulphur, temperature

and time taken for vulcanisation. When we

heat rubber adding 40-45% sulphur, we get

ebonite, a substance with low elasticity.

With the growth of chemistry, we have

been able to make artificial rubber with better

qualities than natural rubber in the laboratory.

Analyse the differences between natural rubber

and synthetic rubber given in table 5.2.

Natural rubber Synthetic rubber

Low hardness high hardness

easily flammable not easily

flammable

Dissolves in Does not react

organic solvents with organic

solvents

Loses stability at Keeps stability at

high temperature high temperature

Less elastic More elastic

Table 5.2

Some commonly used synthetic rubbers,

their properties and uses are given in table 5.3.

Plastics

Different kinds of plastics are familiar to you.

These are also polymers. Plastics are now used

as substitute for wood, stone and metals in many

instances. Prepare and present a project about

the various possibilities of use of plastic objects

and the problems of excessive usage.

Burn a piece of polyester cloth, cool it and

feel it. Does it melt if it is burned again? Repeat

the activity using a polythene cover and record

the results of your observation in your science

diary. You can experiment using the following.

$ nylon rope

$ buttons

$ PVC pipe

$ bottle caps

You have understood that polyester, on

burning, underwent a chemical change and

polythene, a physical change. Plastics that

undergo a chemical change when heated are

Synthetic rubber Property Uses

Styrene butadiene High frictional force tyres

rubber (SBR) Not easily broken foot wears

Resists ozone

Gets easily oxidised

Neoprene rubber Not easily flammable Cable insulation

Does not easily react with oils Conveyer belt in coal

and solvents mines

Stable at high temperature Making hose

Thiokol High elasticity Tanks for storing solvents

Hardness Making seal

Doesn't dissolve in organic solvents

Table 5.3

Chapter 05

62 Chemistry

known as thermosetting plastics and those that undergo a physical change on heating, are known as

thermoplastics. These are listed in the table below.

Name Monomer unit Properties Uses

Thermoplastics

Poly ethylene ethylene Insulator as insulator, as wrappers

( CH2 - CH2 ) n CH2 = CH2 Flexibile for making pipes

Polyvinyl chloride Vinyl chloride insulator manufacturing of pipe, tanks

[ CH2 - CH ] n CH2 = CHCl for chemical process, rain

| coat, helmets etc.

Cl

Nylon Adipic acid and has lusture Fishing nets, clothes,

Hexamethylene strong parachutes, chords etc.

diamine firm

elastic

Thermosetting plastics

Bakelite Phenol + Insulator, making switches,

formaldehyde black in colour soap dishes,

electrical appliances etc.

Polyester Esters of Low density Making body of vehicles

unsaturated Transparent home appliances,

alcohols Strong and firm clothes etc.

Table 5.4

Since thermoplastics become soft on

heating, they can be used again (recycling) to

make new things. Thermosetting plastics cannot

be used again, Why? Try to find out the various

uses of the two types of plastics and the

differences in their properties.

Fibres

Centuries ago, humans learned to make

strong and beautiful things from the thin natural

fibres like coconut husk, cotton, hemp, silk

and animal hair. Before the emergence of

modern technology, such materials were used

by us. All of them are polymers. Polymers of

plant origin are made of cellulose and those of

animal origin with proteins. Though these

polymers could be used for different purposes,

their basic qualities could not be changed.

With the development of modern chemistry we

were able to study more about the qualities of

such substances and make them artificially with

better qualities. Artificial fibres are an

important contribution of polymer chemistry.

Many artificial fibres with wide variety in

qualities like colour, strength, weight, reflective

property, ability to maintain shape and

smoothness are now industrially made. The

astonishing variety in the clothes that we now

use is due to the growth of chemistry.

Chemistry in daily life

Standard 10 63

Figure 5.1

Artificial Fibres

Rayon is regenerated cellulose.

Substances that contain cellulose (e.g. wood

pulp) are first dissolved in carbon disulphide

and then made into pulp by adding alkali. This

is viscose. This viscose is then passed

through very small holes into a dilute acid

solution. In this acid solution, the cellulose

fibres are regenerated. This is known as

artificial silk.

Glass

Glass is one of the widely used substances.

What are the commonly used objects made of

glass?

$ lenses

$ utensils

$

$

Glass is used to make various household

utensils and laboratoryware. The windshield

of a motor vehicle is also made of glass. Are

the properties of all these glasses similar?

Table 5.5 shows different types of glasses, their

constituents and uses.

Examine the table, find out the difference

in properties of each type of glass and record

it in your science diary. Which is the common

ingredient in the above glasses? The

ingredients needed to make soda glass, heat

resistant glass and flint glass are given in the

table. These ingredients are heated at a certain

temperature. We can make glasswares by

pouring the molten substance into moulds or

by blowing.

Safety glass is made by pressing and

binding two glass sheets with a thin plastic

sheet held in between them. These are

laminated glasses.

Fibre glass is made by passing molten

glass through very minute holes in metallic

cylinders. Fibre glass is as strong as steel.

Making artificial silk

Dissolve about 10 g of copper

sulphate in water in a beaker. To this,

add dilute sodium hydroxide. Copper

hydroxide precipitates. Remove this

precipitate using a filter paper.

Dissolve it in concentrated

ammonium hydroxide. To this

solution, add some cotton. Cotton

dissolves in it. Take this solution in

a syringe and inject it into dilute

sulphuric acid in a beaker. You get

synthetic fibres.

Chapter 05

64 Chemistry

Different colours can be given to glass

using different metallic oxides or ions.

Metal compound/ion Colour

Ferric ion Yellow

Ferrous or chromium Green

Cobalt ion Blue

Manganese dioxide Purple

Nickel salt Red

Cupric oxide Red

Cadmium sulphide Lemon yellow

Uranium oxide Greenish yellow

Cryolite/Calcium Opaque milk

phosphate white colour

Table 5.6

Cement

Cement is a man made substance that has

changed the very face of earth. It was with

the large scale manufacturing of cement that

we were able to construct big townships,

cities, factories and many types of buildings.

Cement which becomes soft when mixed with

water can be moulded into desired shapes,

subsequently sets and becomes very hard.

This is what makes cement suitable for

construction works.

What is cement?

Cement is a complex mixture of aluminates

and silicates. Given below are the raw

materials used for this (Table 5.7).

Table 5.5

Chemistry in daily life

Standard 10 65

Manufacture of cement

The raw materials are ground into a fine

powder and mixed in the fixed proportion.

This is heated in a furnace at a high temperature

(15000C). Clinkers, which is a complex

mixture of calcium silicate and calcium

aluminate is formed. Gypsum is added to

clinker and the mixture is powdered to make

cement.

The portland cement that we use

commonly contain the following ingredients.

(Table 5.8).

Cement of olden days

A building material with properties similar to cement was widely used in the past.

This substance is made from lime and is known as slaked lime. When sea shell or

lime stone which contain CaCO3 is strongly heated, CO2 is liberated.

CaCO3 → CaO + CO2

Water is added to the CaO thus obtained and the following reaction takes place.

CaO + H2O

→

Ca(OH)2

Ca(OH)2 - slaked lime - can be shaped as one likes and used for construction works.

Subsequently, on reacting with the CO2 in the atmosphere, it becomes CaCO3 which

is very firm.

Ca (OH)2 + CO2

CaCO3 + H2O

The process which starts with CaCO3 and ends with the same substance.

Table 5.8

Compound Chemical

composition %

Lime CaO 60-67

Silica SiO2 17-25

Alumina Al2O3 3-8

Iron oxide Fe2O3 0.5-6.0

Magnesia MgO 0.1-4.0

Sulphur trioxide SO3 1-2

Soda + potash Na2O + K2O 0.5-1.3

Table 5.7

Compound Chemical composition Percentage

Elite 3 CaO.SiO2 40 - 65

Belite 2 CaO. SiO2 10 - 25

Aluminate 3 CaO Al2O3 Up to10

Ferrite 4 CaO.Al2O3.Fe2 O3 Up to 10

Gypsum Ca SO4. 2 H2O Upto 2 – 5

Chapter 05

66 Chemistry

Action with water

Have you ever thought how cement hardens

when water is added? Many reactions take place

at the same time when water is added to cement.

The aluminates and silicates in cement react with

water and undergo hydration. The hydration of

aluminates takes place very fast. This is the

"setting of cement."

3CaO.Al2O3 + 6H2O → 3CaO.Al2O3

6H2O + heat energy

Substances like gypsum can control the

setting time. You can now explain why gypsum

is added to cement during its manufacture. Is

the setting of cement exothermic or endothermic?

The mixture of cement, sand and water is

called cement mortar. You are familiar with its

use in building construction.

Gravel is added to cement mortar to increase

its strength. This mixture is known as concrete.

This can again be reinforced using steel or iron

rods.

Medicines

The living body is made of chemical

substances. Any foreign chemical substance

that enters a living body can hence react with

body tissues and fluids. By inducing suitable

chemical reactions in the body through

chemicals, diseases can also be controlled.

Chemicals used in this way are known as

medicines. Chemistry helps in identifying

chemical substances that can control disease.

Chemicals that can react with protein

molecules are usually used as medicines. All

the processes in the living body are controlled

through enzymes which are proteins. This is

why chemicals that react with proteins are used

as medicines. For example, when antibiotics

react with enzymes in the bacterial cell they

are destroyed or their growth stopped.

There are certain receptors on the cellsurfaces

which can receive chemical messages

that come from nerves and, also, react with

hormones. These are also proteins. It is

through the reactions with these that medicines

attain the intended effect. Analgesics (pain

killers) work in this way.

From nature to chemistry

Alexander Fleming discovered penicillin

in 1929. This medicine, which could

destroy bacteria, was extracted by him

from a mold. Medical science was able

to eradicate and control many lethal

diseases through this medicine. Though

it was Alexander Fleming who gave us

this medicine that could save the life of

millions of people, chemistry too has a

claim in this success.

Since the quantity of penicillin

separated from mold was very little, it

was sold by pharmaceutical companies

at very high prices. Very soon scientists

discovered techniques to synthesise

penicillin. The anti-bacterial properties

were analysed and scientists were able

to synthesise chemicals with similar

properties. This was made possible by

the progress of chemistry. Chemistry

has enabled us to make many new

medicines.

Chemistry in daily life

Standard 10 67

Along with the ability to conduct such

reactions, chemicals that are used as medicines

must be those that do not cause damage to

other cells and chemical systems.

Antibiotics

Certain chemicals produced by bacteria,

fungus etc. destroy other micro oganisms or

hinder their growth. These are called

antibiotics. Penicillin is an antibiotic that is

widely used. The names of some antibiotics

are given below:

$ penicillin

$ tetracycline

$ ampicillin

$ amoxicillin

$ chloramphenicol

Chloramphenicol is an antibiotic that is

effective against many disease-causing germs.

Since this substance is easily absorbed in the

alimentary tract, this is applied as oral medicine

in diseases like typhoid, cholera, meningitis,

pneumonia etc.

$ Though medicines greatly help protect

and maintain our health, does not their

indiscriminatory use bring about

dangerous side effects?

Discuss the above and conduct a seminar.

Agriculture and chemistry

Agriculture is another field where

revolutionary changes have come about

through the growth of chemistry. When world

population increased rapidly, the need for food

materials also increased. It was impossible to

cater to this increased need through traditional

ways of agriculture. Through modern methods

of farming, food production multiplied tenfold.

'Green revolution' could take place in a country

like India. It was through the application of

knowledge of chemistry that the methods of

farming could be improved. The most

important factor in the modernisation of

agriculture was the use of fertilizers which

helped the growth of plants. What are

fertilizers? How do they act?

Fertilizers

Plants get elements like carbon, hydrogen,

oxygen etc. which are essential for their

growth, from the atmosphere and water.

Besides these elements, sodium, potassium and

phosphorous and small quantities of calcium,

magnesium and sulphur are also needed.

Fertilizers are used mainly to provide these

elements. The elements contained in the soil

are lost through rain water and repeated

farming. Elements needed by the plants can

be immediately made available through

fertilizers. It has been observed that

agricultural yield more than doubles if fertilzers

are used in the proper way.

Nitrogen, phosphorous and potassium are

the most important constituents of fertilizers.

Fertilizers are classified into three types -

nitrogen fertilizers, phosphorous fertilizers and

potassium fertilizers. The problems that arise

due to lack of these elements and the fertilizers

that can be used in such situations are given in

table 5.9 below.

Chapter 05

68 Chemistry

$ chlorination

$

How is water purified by chlorination? Find

out and write it in your science diary.

Chemicals that are used to kill harmful

virus, fungus etc. are called germicides. Find

out more examples.

Like human beings, plants too have

enemies and diseases. Worms, insects,

rodents and weeds are some of these. To

protect the plants from these, we use many

chemicals. These chemicals pollute our soil,

water and air and many harmful effects have

become apparent. Do you know that many

insecticides pose grave threats to generations

of humans and destroy whole ecosystems?

$ Do the insecticides that we apply to the

soil decompose and perish?

$ Does their use cause air pollution?

$ Do they cause water pollution?

$ How do they affect our ecosystem?

$ To avoid this, can you propose

alternatives?

Table 5.9

Element Problems caused by deficiency Fertilizer containing

of the element the element

Potassium Yield and disease resistence reduced Potassium chloride

Potassium sulphate

Nitrogen Cannot make proteins Sodium nitrate, Calcium nitrate,

Ammonium nitrate

Ammonium sulphate

Phosphorous Yield reduced, Fruits does not ripen easily Bone powder

Ability to absorb nitrogen and other Calcium phosphate

elements reduced

Find out the percentage composition of

nitrogen in different nitrogen fertilizers. Can

you say which fertilizer is the better one?

Insecticides

You know that insecticides have had a

great impact in the field of agriculture. Tabulate

the various insecticides and their uses.

Insecticides Uses

1. DDT Control mosquitoes

Baygon and flies

2. Parathion Kills insects that

Sevin destroy crops

3.

4.

Weed killers

These are chemicals that destroy the

weeds.

Eg: Treflan

Calcium cynamide

Germicides

You have heard of purification of drinking

water. What are the methods for this?

Chemistry in daily life

Standard 10 69

SUMMARY

$ Thermoplastics are those that undergo physical changes when heated.

$ Thermosetting plastics are those that undergo chemical changes when

heated.

$ Natural rubber is a polymer obtained from nature.

$ Vulcanisation is the process of improving the properties of rubber by

adding sulphur and heating it.

$ Glass is a mixture of silicates.

$ The compounds of transitional elements can provide colour to glass.

$ Cement is a mixture of silicates and aluminates.

$ The ‘setting’ of cement is due to the hydration of aluminates and

silicates.

$ Pharmaceutical chemistry is of great importance. Chemistry has

contributed greatly in the manufacturing of fertilizers, insecticides,

fungicides, weed killers etc. in the field of agriculture.

$ Chemicals which have the ability to react with proteins are commonly

used as medicines.

$ Fertilizers, insecticides, weed killers and germicides which are the

contributions of chemistry have greatly helped in the improvement of

agriculture.

1. Conduct a study on the dyes used in cotton

and polyester clothes.

2. Find out the chemical ingredients of

insecticides that are commonly used.

3. Write the balanced equation for making

polypropylene.

4. Find out and list the uses of ebonite.

MORE ACTIVITIES FOR YOU

$$$$$$

5. Why is flint glass used for making lenses?

6. Find out the common ingredient in medicines

used for fever.

7. Polythene is not used for making handles of

cooking vessels. Can you explain the

reason?

8. Why is water sprayed repeatedly after

cement plastering has been done?