Class VIII Chemistry | Important Points

INEXHAUSTIBE AND EXHAUSTIBLE NATURAL RESOURCES

NATURAL RESOURCES: Materials or substances that are present in nature are called natural resources.

For example, air, water, etc.

They are divided into two:

1. INEXHAUSTIBLE NATURAL RESOURCES: These are the natural resources which are unlimited and could not be finished by human use. For example, air, sunlight.
2. EXHAUSTIBLE NATURAL RESOUECES: These are the resources which are limited in nature and could be finished if not use in proper manner. For example, forests, coal, petroleum, natural gas, etc.

• Coal, petroleum, natural gas is known as fossil fuels because they are obtained from fossils.
• Fossils- They are the dead matter remains of living organisms.

COAL

Coal is a type of hard stone black in color.

Formation: About 300 million years ago, due to natural process like flood, etc. forest get buried into the

soil and converted to fossils. These fossils, under high temperature and pressure, are converted to coal by process called carbonization.

Carbonization: Coal mainly contains carbon, so conversion of fossils to coal is called carbonization.

USES OF COAL

• Used to cook food.
• Produce electricity in thermal power plants.
• In earlier times used in railway engines.
• In industries to make coke, coal tar, coal gas etc.

• When coal is burnt in air, it gives carbon dioxide gas.

COKE– It is almost pure form of carbon (98% C). It is black in color, tough and porous. Used for making

            steel and extraction of metals such as iron.

COAL TAR– It is a thick black liquid having unpleasant smell. Used in industries for making drugs, paints, naphthalene balls, for making roads, etc.

COAL GAS– It is produced when coal is processed for making coke. Used in industries as a fuel.

PETROLEUM

Petroleum is made up of two words: Petra means rock and oleum means oil. It is naturally occuring dark oily liquid in between the rocks and has unpleasant smell.

Formation: Sea organisms when died settle down at bottom of sea and covered with layer of sand and clay. Under high pressure, temperature and no air present, these dead organisms converted into petroleum and natural gas.

• First oil well was drilled in Pennsylvania, USA.

PETROLEUM REFINING

Petroleum contains different constituents such as petroleum gas, diesel, paraffin wax, lubricating oil, bitumen, etc. Petroleum refining is the process to separate these constituents by fractional distillation.

Petroleum is refined in industrial set up called petroleum refinery.

USES OF PETROLEUM

1. Petroleum gas (LPG) used as fuel in kitchen and industries.
2. Petrol and diesel used to run motor vehicles, aircrafts, etc.
3. Kerosene is used as fuel to cook food.
4. Lubricating oil is used as lubricating agent in industries.
5. Paraffin wax used in candles, ointments, cosmetic products etc.
6. Bitumen is used in paints, and making roads.

• As petroleum has great commercial uses it is called as BLACK GOLD.

NATURAL GAS

Natural gas is naturally occuring gas formed from fossils. It is an important fossil fuel as it is easy to transport from pipes.

Compressed natural gas (CNG) is natural gas compressed under high pressure. It is causes very less pollution so called as cleaner fuel.

• In India, natural gas is found in Tripura, Rajasthan, Maharashtra and Krishna Godavari Delta.

USES OF NATURAL GAS

1. Used for domestic purposes like cooking food.
   1. Used for power generation.
   2. In vehicles, as a fuel to run them.
   3. Manufacturing chemicals and fertilizers.
   • PETROCHEMICALS: Petroleum and natural gas are used for producing many useful substances so they are called as petrochemicals.
   • Burning of fossil fuels causes air pollution. So they should be used only when really required.
   • Petroleum Conservation Research Association (PCRA) in India, gave some advises to save petrol/diesel:
   • Drive at constant and moderate speed.
   • Switch off the vehicles when you are waiting.
   • Correct tier pressure.
   • Regular maintenance of vehicles.

Combustion is a chemical process in which a substance gives out heat when it is reacted with oxygen.

There are two kind of substances –

• Combustible substances – These substances can go through the process of combustion. For example -paper, coal, matchsticks, petrol, diesel, etc. These are also called as

     **They produce heat and light on combustion.

• Non-combustible substances – These substances do not go through the process of combustion. For example – stone, glass, sand, cement, etc.

    ** In sun, the light we see and its warmth or hotness is due to the Nuclear reactions processing in it.

CONDITIONS REQUIRED FOR COMBUSTION OF A SUBSTANCE –

There are certain requirements for combustion –

• The substance should be combustible (it should be a fuel)

For example – a piece of paper is easily burnt but straw does not.

• Availability of oxygen or air – Key component of combustion is oxygen.

For example – if a candle is burning and we cover it with something say flask or glass, then after sometime it stops burning. This is because, after putting glass we have cut oof the supply of oxygen or air.

• Ignition temperature – This temperature is the minimum or lowest temperature at which any substance catches fire. Ignition temperature varies from one substance to other.

For example – a matchstick does not burn itself at room temperature. This is because its ignition temperature is higher than the room temperature. When it is rubbed alongside of matchstick, the temperature of its surface rises and reaches its ignition temperature then it catches fire and we say matchstick is burned.

INFLAMMABLE SUBSTANCES – As the word ‘flame ‘is in its name, it means it is somewhat related to flame. There are substances which have low ignition temperature. Due to this they catch fire very rapidly and burn with flame. These substances are called Inflammable substance.

For example – LPG (liquified petroleum gas). It is used in our home’s gas cylinders for cooking food and it burns with a blue flame.

TYPES OF COMBUSTION – There are three types of combustion –

• Rapid Combustion – In this type combustion happens within a very short period of time with large amount of heat and light. For example – burning of gas stove, burning of candle giving wax, etc.
• Spontaneous Combustion – This combustion takes place at room temperature. The substance going through this combustion have very low ignition temperature. In this, the material suddenly bursts out on its own. For example – phosphorous which burns at room temperature, forest fires (due to the heating when there is lightning), spontaneous combustion of coal dust, etc.
• Explosion – It is a very sudden reaction or combustion which results in large amount of heat, light and sound. For example – burning of firecrackers, etc.

To control fire, it is necessary that the contact of fuel and oxygen or air is cut off.  There are three types of fire which can happen –

1. Substances like wood are on fire – For this kind of fire, Water is used to make it off or extinguish. It brings down the temperature of fuel as well as cuts off the contact of fuel with air. For example – in case of paper.

2. Oil or Petrol fire – Oil or petrol are lighter than water. This means oil or petrol will slip over water. Or simply, water will sink down (as it is a rule that heavier will sink down and lighter will come up). This means the contact of oil or petrol will still remain with air and there will be no extinguishment of fire.

3. Electrical equipment – We know that water is a good conductor of electricity. And if it is used to off the fire of any electrical equipment, it will conduct the electricity and damage the equipment.

Now for situation of 2 and 3, we cannot use water. For these situations FIRE EXTINGUISHER is used. It contains CO₂ in it. CO₂ is heavier than oxygen, so it comes over it and cuts off the contact of oxygen and fuel or substance burning. Moreover, in electrical equipment, it does not cause any  damage.

In the fire extinguisher, CO₂ is kept in liquid form by applying a high pressure over it. CO₂ cuts of the contact with air and also brings down the temperature of substance burning which makes it cool and below its ignition temperature.

Another way to get CO₂ is by releasing a lot of dry powders of chemicals like NaHCO₃ or KHCO_3.

Flame is the region where burning of the substance takes place.

The substances which are vaporized on burning, give flames. For example, wax etc.

The substances which are not vaporized on burning do not give flames. For example, charcoal, etc.

STRUCTURE OF FLAME

There are 3 zones in flame:

1. NON-LUMINOUS ZONE:

• It is the outermost zone of the flame.
• Complete combustion takes place in this zone.
• Color of flame in this zone is blue.
• Hottest zone.
• Goldsmiths uses this zone to melt gold and silver from the blow pipe.

2. LUMINOUS ZONE:

• It is the middle zone of the flame.
• Partial combustion takes place in this zone.
• Unburnt carbon particles are present. It appears as circular black ring on glass plate or slide when the plate is hold on to flame for few seconds.
• Color of flame in this zone is yellow.
• Moderately hot zone.

3. DARK ZONE:

• It is the innermost zone of the flame.
• Unburnt vapors are present in this zone.
• Color of flame in this zone is black.
• Least hot zone.

A fuel is a substance which produces heat or energy when it is burnt. For example, coal, wood, kerosene oil, natural gas, biogas, petrol, cow dung, etc.

It is of 3 types:

1. Solid fuel: Fuel which is hard. For example, coal, wood, etc.
2. Liquid fuel: Fuel which is in liquid form. For example, petrol, kerosene, etc.
3. Gaseous fuel: Fuel which is in gas form. For example, biogas, hydrogen, etc.

An ideal fuel should have features like:

• Easily available and have low price.
• Easily burnt in air.
• Produces large amount of heat.
• Do not cause pollution.

FUEL EFFICIENCY

Different fuels produce different amount of heat.

Fuel efficiency is the amount of heat fuel produces on combustion. Its value is given by calorific value.

CALORIFIC VALUE

Calorific value is the amount of heat produced by combustion of 1Kg of fuel. Its unit is Kilojoule per kg (kJ/ kg).

HARMFUL EFFECTS OF BURNING OF FUEL

1. ASTHMA: Unburnt carbon particles are released when fuel containing carbon like petrol, coal, wood is burnt in air. These particles cause respiratory diseases such as asthma.

2. CARBON MONOXIDE: Carbon monoxide gas is released on incomplete combustion of fuel. It is a poisonous gas which can cause death. So, coal should not be burnt in a closed room.

3. GLOBAL WARMING: It is the rise in the temperature of atmosphere of the earth. Combustion of fuels gives out carbon dioxide gas which can cause global warming. Rise in temperature of the earth leads to melting of glaciers, increase in sea level, floods, etc.
4. ACID RAIN: Acid rain is the rainwater consisting of oxides of sulphur and nitrogen. Sulphur dioxide gas is produced by burning of coal and diesel which causes suffocation. Nitrogen oxides are released from petrol engines. These gases dissolve in rain water. pH of rain becomes acidic, so it is called acid rain. Acid rain is harmful for the crops, soil, buildings, etc.
5. DEFORESTATION: It is the cutting down of the trees from the forests. Trees are cut down for obtaining wood which is used as fuel. It is harmful for the environment.*CNG (Compressed Natural gas) causes less pollution. So, it is called as cleaner fuel.

Every thing in this nature is made up of small units called as Atoms. In atoms there are electrons, protons and neutrons.

Let’s take two elements – A AND B.

A gives its electrons to B, then A will get a positive charge over it and B will get a negative charge over it.

METALS – These are the substances which give electrons to other elements and gain positive charge over them.

PHYSICAL PROPERTIES –

• MALLEABILITY – Malleability is property which means if the substance can be beaten into thin sheets. It is done by beating the material hard by hammer or any other tool. Metals are malleable. For example: aluminium foil used for wrapping food in tiffin.
• DUCTILITY – Ductility is property which means a material can be drawn into wires. Metals are ductile. For example: copper wires, aluminium wires, etc.
• SONOROUS – This property means when something is hit hard then it produces sound. Metals are sonorous.
• HARDNESS – Metals are hard.
• CONDUCTORS – Conductors means the substance which allows something to pass through it. Conductors of heat and electricity means substances which allows heat and electricity to pass through them. Metals are good conductor of heat and electricity. It means that they allow heat and electricity to pass through hem.
• Metals are in solid form generally at room temperature.

**IT IS IMPORTANT TO NOTE THAT ALL METALS ARE HARD BUT POTASSIUM AND SODIUM ARE VERY SOFT THAT WE CAN CUT THEM WITH HELP OF KNIFE.

**ALL METALS ARE SOLID AT ROOM TEMPERATURE BUT MERCURY IS A METAL WHICH IS LIQUID AT ROOM TEMPERATURE.

CHEMICAL PROPERTIES –

• REACTION WITH OXYGEN –

Metal + Oxygen –> Metal Oxide

For example:

Magnesium + Oxygen –> Magnesium Oxide

2Mg + O₂ —>  2MgO

If you have magnesium ribbon open in air then there will be formation of magnesium oxide which is white in colour.

Similarly, if a copper vessel is left open in air then copper will get oxidized by oxygen present in air 2Cu + H₂O + O₂ + CO₂—> Cu (OH)₂+ CuCO₃

Here this mixture of Cu (OH)₂+ CuCO₃ is of green colour.

   **Oxides of metals are basic in nature.

• REACTION WITH WATER –

Metal + Water —  Metal hydroxide + H₂

2Na+2H2​O→2NaOH+H2

Sodium reacts vigorously with water. That is why it is kept in kerosene as a lot of heat is evolved out. But there are some metals which act slowly with water like iron.

• REACTION WITH ACIDS –

Metal + Acid — Metal salt + H₂

For example- Zn + H₂SO₄ –à  ZnSO₄ + H₂

So, here ZnSO₄ is the metal salt along with production of hydrogen gas.

Metals when reacts with acids, form hydrogen gas. And if we burn this hydrogen then it will burn with a pop sound.

**COPPER REACTS WITH SULPHURIC ACID BUT NOT WITH HYDROCHLORIC ACID.

• REACTION WITH BASES-

Metals + Base —  Metal hydroxide + H₂

For example:

2NaOH+Zn⟶Na₂​ZnO₂​+H₂​

Here also, hydrogen gas is produced.

• DISPLACEMENT REACTION –

The word displace means when one substance comes over the place of other. So, in this reaction one element displaces or comes over the place of another element.

But for one element to displace other element it is necessary that is should be more powerful than another element.

For example:

CuSO4 + Zn –>  ZnSO₄ + Cu

In this reaction zinc is able to displace copper because it is more powerful than copper.

For knowing which element is more powerful we have REACTIVITY SERIES –

In the reactivity series as we go up, elements become more powerful.
USES OF METALS – Metals are essentially used for making utensils, aeroplanes, machines, trains, etc.

Nonmetals are the elements which accept the electrons from other elements and gain negative charge.

Some of the nonmetals are hydrogen, chlorine, bromine, carbon, sulphur, phosphorus, iodine, etc.

PHYSICAL PROPERTIES OF NON-METALS

1. They are soft. For example, coal.
2. They are not lustrous and sonorous.
3. Do not show the properties- malleability and ductility.
4. Poor conductors of heat and electricity.

 CHEMICAL PROPERTIES OF NON-METALS

1. REACTION WITH OXYGEN:

Nonmetal + O₂ —–> nonmetal oxide

• Nonmetal oxides are acidic in nature (turns blue litmus paper to red)

For example, Carbon (C) + O₂ ——>    CO₂ (carbon dioxide)

Sulphur (S) + O₂——>   SO₂ (sulphur dioxide) ——> H₂SO₃ (sulphurous acid)

2. REACTION WITH WATER:

Nonmetal + water (H₂O) —-> No reaction

• As nonmetals do not react with water, so they can be kept in water to prevent them from reacting with air. For example, phosphorous catches fire if exposed to oxygen, so it is kept in water.

3. REACTION WITH ACID AND BASE:

• Nonmetal + Acid —–> No reaction

• Reaction of the nonmetals with the bases is complex reaction.

AIR POLLUTION

In air there is 78% of nitrogen and 21% oxygen (by volume). Other gases like Carbon dioxide, argon, methane, ozone and water vapors are also present in air but their proportion is very small.

Pollution – This term means when unwanted substances get mixed and contaminate (make it dirty) Air.

Air Pollution – It means that air is contaminated with unwanted substances. As Air is necessary for breathing of every human and animal on earth, its harmful effect causes damage to animal life on earth. There are many reactions with air of  nonliving things which means they are also affected by this air pollution.

HOW AIR GETS POLLUTED?

The materials or substances which causes air pollution or are responsible for the same are called Air Pollutants. Different ways of air pollution are –

• Some natural factors like forest fires and volcanic eruptions. They give rise to smoke and dust which ultimately goes in atmosphere and causes air pollution.
• Incomplete burning of fossil fuels like petrol or diesel leads to formation of Carbon Monoxide. Carbon Monoxide is a very harmful – poisonous gas as it decreases the blood’s capacity for carrying oxygen.
• Formation of smog. Smog is mixture of smoke and fog. It contains nitrogenous oxides which results in asthma, wheezing in children, cough etc.
• Pollution caused by industries. For example, Petroleum industries release sulphur dioxide and nitrogen oxide in air.  After combustion of coal in power plants, this sulphur dioxide is released in air which results in permanent lungs damage, other respiratory problems etc.
• CFC’s (chlorofluorocarbons). These are used in air conditioners, refrigerators, deodorants, perfumes, etc. They cause damage to our earth’s UV protector OZONE layer.
• Tiny particles which are released while burning of petrol or diesel in automobiles, remain suspended in air. It leads to decrement of visibility.

CASE STUDY -TAJ MAHAL

Acid Rain – When Sulphuric and nitric acids are mixed up in air and the rain comes down, this rain is called as acid rain. This acid is formed when gases like sulphur dioxide and nitrogen dioxide go up in air and react with water vapors present in air itself.

When this acid rain falls upon the monument (here Taj Mahal), it corrodes the marble and this is known as ‘Marble Cancer’.

SPM (suspended particulate matter) emitted by Mathura oil refinery has contributed towards yellowing of the marble.

Measures have been taken by Supreme court like –

• It has ordered industries to use CNG (compressed natural gas) and LPG (liquified petroleum gas)
• Automobiles should switch to unleaded petrol (petrol which does not have lead in it.)
  

  GREENHOUSE EFFECT

  Some part of Sun’s radiation falls on earth. The reflection phenomenon takes place. But not all part of radiation is reflected back, some part of it is trapped by earth’s atmosphere. This trapped radiation helps to give warmth to earth.  This trapping of radiation of sun is called as ‘greenhouse effect’. This effect is important aspect for existence of life on earth.

  GLOBAL WARMING

  Plants give us oxygen and take carbon dioxide. The highly increased rate of deforestation leads to decrease in number of plants and trees. Which means there is decrease in amount of oxygen as well as increase in amount of carbon dioxide. There are other human activities too which results in emission of carbon dioxide.

  Excess CO₂ acts as pollutant in air and causes air pollution. As CO₂ traps heat and does not allow it to escape out , it results in increase of earth’s average temperature. This phenomenon is called ‘GLOBAL WARMING’.

  ** Effects of Global Warming –

  • Rise in sea levels
  • Effects on rainfall, agriculture, forests, etc.

  Greenhouse gases – carbon dioxide, methane, nitrous dioxide and water vapors.

  Many nations have started to look at this serious problem and making agreements to reduce pollution. For example -Kyoto Protocol.

  WHAT MEASURES CAN WE TAKE?

  • Using CNG and unleaded petrol.
  • Generating awareness among people about this issue.
  • Switch to solar energy, hydropower and wind energy

Planting trees and practicing afforestation (means to grow more and more trees)

WATER POLLUTION

When unwanted substances like dirt, toxic chemicals, silt, etc. contaminate the water or make it unfit for

consumption, it is called as Water Pollution.

These toxic chemicals, silt, dirt, sewage, etc. which pollutes water are called as Water Pollutants.

CASE STUDY: RIVER GANGA

Ganga is source of livelihood to millions of people. According to WWF (worldwide fund for Nature) has claimed Ganga to be in the ten most endangered rivers in the world. It is polluted to a very high extent due to –

• Throwing of large amount of garbage in it
• Dead bodies
• Untreated sewage
• Toxic chemical in it
• Waste from industries and factories

For reducing the waste in river or saving the river, a plan was launched in 1985 as ‘GANGA ACTION PLAN’

Now Indian government has again launched an initiative as ‘National Mission for Clean Ganga’ in 2016.

HOW INDUSTRIES ARE RESPONSIBLE FOR POLLUTING WATER?

They discharge highly toxic chemicals (like arsenic, fluorides and lead) in water bodies. For example – sugar mills, textile factories, etc. Due to the untreated chemical waste flushing in water bodies, not only water is polluted but there is damage to soil too leading to growth of worms and change of acidity scale.

HOW POOR AGRICULTURE ACTIVITIES DOES WATER POLLUTION?

The pesticides and insecticides which are put on crops get washed away with water and dissolve in water. The same water goes in the water bodies and pollute them. Even groundwater is also polluted as many times this water gets deep in the ground.

This excessive amount of chemicals leads to formation of algae as these are the nutrients for algae. Even when this alga dies, there decomposition by bacteria uses up a lot of oxygen which results in lack of oxygen for aquatic life.

HOW SEWAGE LEDS TO WATER POLLUTION?

Untreated sewage containing food wastes, detergents, micro-organisms etc. is directly thrown in water bodies. This sewage contaminated water contains bacteria, viruses, fungi and parasites which cause diseases like cholera, typhoid and jaundice.

In mammals if there is faeces (a bacteria) it indicates that that water is contaminated and unfit for human consumption.

HOW HOT WATER FROM INDUSTRIES POLLUTES WATER BODIES?

Industries use cool water for many purposes like for cooling their machineries. After this the water becomes hot and no use for factories so they directly throw that water in water bodies. This hot water increases water body’s temperature. This have a very negative impact over the aquatic life.

POTABLE WATER

Potable water means that water which we can drink. Means which is free from contamination and is fit for our

consumption.

Ways by which we can make water suitable for drinking –

• Filtration of Water – it is a physical method for purifying water. For example – candle type filter
• Boiling – Due to boiling, the germs present in water are killed.
• Chlorination – This means adding chlorine tablets or bleaching powder to water.

** But it is very important to add chlorine tablets or bleaching powder in a precise manner and not to add them  more than a limit as it is will cause harm to water as well as to those who drink it or use it.

HOW CAN WE REDUCE WATER POLLUTION?

• • • There should be strict laws made for industries and factories. Checks should be made upon them so that properly treated water is thrown in water bodies
    • In all industrial areas water treatment plants should be made
    • We as individual should follow Reduce, Reuse and Recycle statement.
      

       

FABRICS 

The substance which we get from fibers are called fabrics. Fibers can be obtained from natural or artificial resources.

Natural resources – The resources which are provided by nature through plants and living organisms.

Artificial resources – The resources which are developed by humans.

Fibers are even used for making many daily use products or household things. Types of fibers includes –

Natural fibers – The fibers which are obtained from either plants or animals, means obtained from nature.

 For example:  cotton (from its plant), silk (from silkworm) etc.

Synthetic fibers – Synthetic means one which is synthesis or one which is made artificially. The fibers which are

prepared by man by use of machinery, science, and technology.

For example – Artificial silk, plastic, etc. These are also known as man-made fibers.

SYNTHETIC FIBRES – Synthetic fiber can be understood as a chain of small chemical substances (called as unit) joined together.

The small units combine to form a big unit which is called a Polymer.

TYPES OF SYNTHETIC FIBRES –

1. RAYON – It is also called as Artificial Silk. It is obtained when wood pulp is treated chemically.

• Its cost is less than natural silk.
• Like natural silk fiber, this can also be woven.
• We can also dye this and use it in different colors.
• It is mixed with cotton to from bedsheets.
• It is mixed with wool to make carpets.

   ** Rayon is considered as synthetic (yet it is obtained from a natural source)

2. NYLON – This was the first synthetic fiber discovered. It is made without use of any natural raw material.

• Coal, air, and water are used to prepare it.
• It is strong, elastic and light.
• It has shiny appearance (lustrous)
• It is easy to wash.
• It is used to make ropes, tents, socks, bags, toothbrushes, etc.
• It is also used to make Parachutes
• It is used for making ropes (for rock climbing)

** It is very important to note that these Nylon wires are even stronger than Steel wire.

3. POLYESTER – This fiber has quality that it does not get wrinkled easily.

• It is easy to wash
• It is a suitable material to make dresses
• For example- Terylene – we can weave it as it can be drawn into very fine fiber
• For example – PET (polyethylene terephthalate) – used for making bottles, utensils, films, etc.

4. ACRYLIC – It is synthetic fiber which is used to make sweaters and blankets. Its

• Clothes of acrylic fiber are cheaper than that of natural wool.
• It is available in variety of colors.
• Acrylic fiber can be used much longer than natural fibers.

CHARACTERISTICS OF SYNTHETIC FIBRES –

• They have property to dry up quickly
• They are more durable than natural fibers
• They are cheaper
• Are readily available means they are easily available and very quickly too.
• Their maintenance is easier than natural fiber

BUT IT IS VERY IMPORTANT TO NOTE THAT the main risk of synthetic fibers is that they get melted on heating.

Synthetic fiber catches fire very easily and very quickly. After catching fire, they stick to the body of person who is wearing them, which causes harm to the person’s skin.

PLASTICS

Plastic is a polymer made up of small units arranged in chain or cross-linked pattern.

THERMOPLASTICS: They are the plastics which can be bent easily on demolding them on heating. For example, Polythene (poly + ethene), PVC, Toys plastic, etc.

THERMOSETTING PLASTICS: They are the plastics which cannot be changed once they are molded. For example, Bakelite and melamine.

• Bakelite is used for making switches, handles of utensils as they are poor conductors of heat and electricity.
• Melamine is used for making crockery, uniform of fireman as they are fireproof and tolerate more heat.

PROPERTIES OF PLASTICS

1. They can be made into any shape.
2. They are cheaper and light in weight.
3. They do not corrode.
4. They are durable and strong.
5. Poor conductors of heat and electricity.

USES OF PLASTICS

1. Polythene bags are made from polythene.
2. They are used for making toys, bottles, containers, comb, furniture, etc.
3. Used for making parts of vehicles, aircrafts, etc.
4. Used in making gloves, tablet packets, syringe, etc.
5. Teflon is a plastic used for making non- stick utensils because on oil and water do not stick on Teflon.

   BIODEGRADABLE AND NON BIODEGEADABLE MATERIALS

   BIODEGRADABLE MATERIALS: These are the materials which decompose by bacteria through environmental processes. For example, paper, wood, cotton, vegetable and fruit peel, etc.

   NON-BIODEGRADABLE MATERIALS: These are the materials which are not decomposed easily by environment. For example, plastics, tin, aluminium, other metal cans, etc.

   • Plastics cause pollution as they do not decompose easily and take several years for it.
   • On burning plastics, toxic fumes are released which cause air pollution.
   • If plastics swallowed by animals, their respiratory system gets choked and can cause death.

   Prevention-We can prevent pollution by:

   • Avoiding the use of plastic as much as possible.
   • Use of cotton or jute bags rather than polythene bags.
   • Throw off biodegradable and non-biodegradable waste separately in different dustbins.
   • Follow 5 R principle-
     • Reduce
     • Reuse
     • Recycle
     • Recover
     • Refuse