Essential for Life : Air and water

Essential for Life : Air and  water 

Air is present all around  us . we Cannot see or smell air but can feel its presence when it moves . Air is necessary for the existence  of life .

Atmosphere 

Our earth is surrounded by a blanket of air  called atmosphere  . Atmosphere is present many kilometer above the earth's Surface . As we go higher up in the atmosphere, the amount  of air become less .that is why, mountaineer take oxygen cylinders with them . the gravity pulls  the layers of airs towards the surface of the earths Layers  of the atmosphere The atmosphere has the five main layers 

1. Troposphere : It is the lowest layer . all the  changes in weather occur here .

2.Stratosphere: It is present  above  the  troposphere ozone gas present in this  layers, absorbs the harmful UV rays coming  from the sun  and prevents  them reaching the earths  surface. These  rays are very harmful to us 

3.Mesosphere: It is the third layer Meteoroids and small rocks moving in space are burnt out here . Thus , They do not  reach the earths 

4.Thermospheres : It is the fourth layers . Space shuttles in this layer.

5.Exospheres : It is the outermost layer.

 

 Importance  of atmosphere:

1.All living things (plants and animals) get oxygen to breaths from the atmosphere .

2.It maintain the temperature on the earths for the survival of living things 

3. it burns  the meteoroids before they rich  the earth's surface .

4.It protects us  from the the harmful radiations .

Composition of air 

 Air is a mixture of  many gases . about 78 %  nitrogen, 21% oxygen and 1% other gases  like , neon , argon, carbon dioxide  and  ozone present in the air . it also contains  water vapor  and dust particles .

1.Oxygen:

All organism need oxygen for breathing  oxygen is also necessary for burning .

2.Nitrogen: All organism need nitrogen  for their growth . But they cannot use nitrogen directly from the air .Most  of the plants  take nitrogen from the soil. nitrogen is added to the soil through fertilizers. Animals get nitrogen from the  food  food  they eat. nitrogen does  not support burning .

3.Carbon Dioxide : Green plants  use carbon dioxide  to make  their food . it is also used in the fire extinguishers to put out fire .

 

4. Water Vapour:

 Water vapor is formed by the evaporation of water from oceans , rivers and lakes because of the  heat of sun. The amount of water vapor  present in the air is called  humidity . The Water vapor can change the weather 

5. Other Gases:

Air also contains hydrogen , ozone, helium, neon, argon, etc.

Properties of air :

1.Air Occupies space 

2.Air has Mass

3.Air Exerts pressure : We know that air occupies space and has mass. anything that has mass exerts pressure . So , air also exerts pressure . The pressure exerted by air is called atmospheric pressure .

4.Air can be Compressed: Since the molecules of air of gases in air  are  far apart from on  another, air can be compressed and pushed into small spaces 

5. Air Expend  on heating and Contracts on cooling:

When air is warmed ,it expands  and takes up more space , on the  other hand , when air is cooled, it shrinks  and occupies less space .

Importance  of air pressure : Air is  pressure  helps in the  every day life like in filling up a syring and a fountain pen, drinking  with straw and  using  droppers. when you drink juice with a straw , the air  inside the straw is removed while sucking. the pressure of air inside the straw  becomes less .The air  pressure outside at the surface of the juice is more . Air pressure on the surface of the juice then forces the juice  to move up the straw . The dropper  also works  in the same way.

Water

All organism need  water . Three -fourths of our earths  surface is covered with water Only 3% of total available water can be used for drinking .97% of water is in the  oceans . It contains  salts and cannot be used for drinking .

 

How we get Water

 We Get water from rivers, ponds, lakes and rains. We also get water from the ground by using wells, hand pumps, etc. The water in the lake, river , ponds etc., is not pure .Many things  like dirt's  , mud and germs  are mixed with water and make the water unfit for use. The substances that make the water unfit  for  use are called impurities impurities are of two types - Soluble  and insoluble 

1.Soluble impurities : The impurities that get dissolved in water is called soluble impurities . For Examples , Salt of potassium and magnesium .

2.Insoluble impurities : The impurities that do not get dissolved in water is called insoluble impurities . for examples , Sand and Mud.

Removal of impurities from water :

1.Insoluble impurities  like sand can be removed by  using the following methods:

(a) Sedimentation : in this methods a mixture of water and insoluble impurities is allowed to stand  undisturbed in a container for some  times . The heavy insoluble impurities settle down at the bottom of the container . this  layer of impurities is called sediment . when the impurities settle down, clear water is left above the layer of impurities . This process is called sedimentation.

(b) Decantation: After sedimentation the clean water is poured gently int a separate container  without  disturbing the sediment  of impurities  the process is called decantation .

 The rate of sedimentation can be increased  by adding  chemicals like alum.This is called loading.

(c) Filtration: This method is used to separate water from insoluble impurities like mud and sand by using a filter paper.To filter a mixture of water and sand, a cone of filter paper is made and kept inside a funnel. the mixture is poured into the funnel. sand does not pass through the filter paper and remains behind on the filter paper. this is called residue.The clear water comes out of the filter paper and is collected in the flask below the funnel. this is called filtrate. this method of purifying water is called filtration.

2.  Removal of Soluble Impurities

Soluble impurities can be removed by the following two methods:
(a)  Evaporation: In this method, the solution containing soluble impurities like salt is heated. After some time, water gets evaporated (changes into steam) and the impurities are left behind.

(b)  Distillation: Both impurities and pure water are obtained in the process of distillation. in distillation, impure water is heated in a flask. on heating, water changes into steam and impurities are left behind in the flask. steam passes through the condenser.
Here, it cools and changes into water again. this water is pure and is collected in a separate flask.

 

 

PURIFICATION OF DRINKING WATER

Impure water is harmful to us and leads to many diseases. so, we must drink pure water. we can purify water by using the following methods:
1.    Boiling:  Water is heated for 10minutes. boiling kills the germs present in water and makes the water pure. it is the simp0lest way to purify water.

2.    Chlorination: Addition of chlorine tablets in water to kill germs and to make water pure is callled chlorination.


3.    Water Purifier: Nowadays,electrical water purifier is used to get pure water. in most of the houses, RO water purifier is used.