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Air-The mixture of gases which from the earth is atmosphere and which we breathe is called air.
The properties of air are:
Air takes up space.
Air has mass.
Air exerts pressure.
Air can be compressed.
Atmosphere-The thick envelope of air surrounding the earth is called atmosphere.
It is one of the natural components of the environment.
Functions of Atmosphere:
It provides us the air we breathe.
It protects us from the harmful effects of sun’s rays.
It prevents the earth from becoming too hot or too cold.
Composition of Air:
The air that we breathe is a mixture of many gases like oxygen, nitrogen, carbon dioxide, argon etc.
The majority of the atmosphere is made up of nitrogen (78%) and oxygen (21%).
The other gases that are present in small quantities are: Carbon dioxide (0.03%), Argon (0.93%) and others (helium, hydrogen, ozone).
Tiny dust particles are also present in the air, apart from the above gases.
Nitrogen:
It is the gas that is most abundant in the air.
Plants need nitrogen to make protein.
Plants cannot take the gaseous nitrogen from air.
Some bacteria live in soil and in roots of some plants.
Oxygen:
It is the second most plentiful gas in the air.
Oxygen plays an important role for human beings, animals and plants in the following ways. Most of the living beings need oxygen for respiration.
Green plants produce oxygen during photosynthesis.
Carbon dioxide:
It is another important gas.
Green plants need carbon dioxide to carry out photosynthesis.
Most of the living beings release carbon dioxide during respiration.
Structure of the atmosphere:
Our atmosphere is divided into five layers which are:
Troposphere: It is the most important layer of the atmosphere.
Its average height is 13 km.
The air we breathe exists here
Almost all the weather phenomena occur in this layer.
The weather phenomena include: Rainfall, Fog, Hailstorm etc.
Stratosphere: This layer is just above the troposphere.
It extends to a height of 50 km. It is almost free from clouds and associated weather phenomena that occur in the troposphere.
It is most ideal for flying aeroplanes since it is free from weather phenomena.
It contains a layer of ozone gas which protects us from the harmful effect of ultraviolet rays from the sun.
Mesosphere: It is the third layer of the atmosphere and it lies above the stratosphere.
It extends up to a height of 80 km.
The burning of meteorites on entering from space occurs in this layer.
Thermosphere: It is the fourth layer and the layer above the mesosphere.
In this layer, temperature rises very rapidly with increase in height.
Ionosphere is a part of this layer. It extends between 80 to 400 km
It helps in radio transmission. This layer is responsible for reflecting back of the radio waves that are transmitted from the earth.
Exosphere: It is the uppermost layer of the atmosphere.
It has very thin air. Light gases like helium and hydrogen float into the space from here.
Air and its uses:
Air is needed for Breathing
All living beings need oxygen to breathe Oxygen is used by animals to produce energy.
The oxygen goes into the lungs.
From there it is carried by the blood to every part of the body.
Food is burnt there by oxygen and carbon dioxide is produced and thrown out from the lungs. This process is called respiration.
Air Carries sound
Air helps us to listen to the sounds around us.
Without air, the drum would beat but you won’t hear it.
It is because sound needs a medium to reach us.
Air Pressure is Important in Daily Life
Air pressure plays an important role in our daily life.
Many things like syringe, dropper, drinking straw, hand pump and many other things work on the principle of air pressure.
Some other uses of air are given below:
Oxygen in the air helps in burning.
If there is no air there will not be any fire.
Nitrogen present in air is an important nutrient for plants.
Nitrogen is also used in making many fertilizers.
The marine plants and animals use air which is dissolved in water.
It is used to produce electricity and to do mechanical works.
Air pollution – A type of environmental pollution that affect the air and is usually caused by smoke or other harmful gases are called air pollution.
Causes of air pollution:
Burning of fossil fuels like coal, diesel and petrol.
Smoke from factories pollutes the air.
Deforestation increases the amount of carbon dioxide.
Volcanic eruption in some places also can pollute the air.
Effects of air pollution:
Greenhouse effect
Acid rain
Destruction of the ozone layer
Water-A clear liquid, without colour or taste, that falls from the sky as rain is called water.
About 70% of the earth made up of water.
Importance of water:
Domestic Purposes – Cooking, Drinking, Bathing, and Washing.
Agricultural Purposes – Farming gardening fisheries.
Industrial Purposes – Manufacturing.
Recreation – swimming. Rafting. Boating.
Hydropower generation.
Impurities in water–
Impurities – Substances that are present in small quantities in another substance and make it dirty are called impurities.
We should drink only clean water; unclean water can make us ill.
Clean water fit for drinking is called potable water.
Very little amount of the water available on this earth is potable.
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Soluble impurities- Those impurities which can be dissolving in water are called soluble impurities.
Insoluble impurities- Those impurities which cannot dissolve in water are called insoluble impurities.
Removal of insoluble impurities:
Insoluble impurities can be removed by the following process –
Filtration – The process of removing the insoluble particles from water by using a filter is called filtration.
Sedimentation – The process of particles settling to the bottom of a body of water is called sedimentation.
Decantation – The clear water on the top is slowly poured out without disturbing the sediments. This process is called decantation.
Removal of soluble impurities: Soluble impurities can be removed by –
By boiling
By adding Chemicals
By using water purifiers.
Evaporation
The impure solution with impurities such as salt or sugar is heated till all the water evaporates. The impurity is left behind in the evaporating dish.
Distillation: The process of distillation involves the following steps.
The impure water taken in a flask is heated.
On heating, water is converted into steam and the impurities are left behind,
When the steam is cooled after passing through the condenser, it turns into liquid water. The pure water called distillate is collected in a conical flask.
Purification of water:
Boiling:
This is the easiest and the most common method to purify water before drinking.
Boiling kills the germs present in it.
Remember that boiling should be continued for at least 10 minutes
Distillation:
The water stored through the process of distillation is the purest form of water.
It is free from germs.
It is widely used as distilled water in injections, medicines and car batteries.
Chlorination:
In this method the tablets of chlorine are added to the container where thewater is to be cleaned.
Chlorine tablets kill germs and make the water pure.
