Air and water notes

INTRODUCTION

•      The two most important things without which we won't be able to live are air and water.

•      The air is all around us in our environment, and we take it in when we breathe.

Figure 1: Use of water in various ways

•      This air consists primarily of oxygen and nitrogen in addition to small amounts of other gases, bacteria, and viruses.

•      Water is important to us in many ways.

•      It is used for:

AIR

•      The air that surrounds us is a mixture of several gases.

Figure 2: Pie-chart of air composition

•      Air is colourless and tasteless and is made up of about 78% nitrogen, 21% oxygen and 1% is composed of small quantities of other gases such as carbon dioxide, ozone, hydrogen, helium etc.

•      It is the Earth’s gravity that holds the layer of air around our planet.

Oxygen:

•      Oxygen is a colourless, tasteless, gaseous element which forms 1/5 of the earth's atmosphere.

•      One oxygen molecule is made up of two atoms of oxygen.

PROPERTIES OF AIR

•      Air can be greatly compressed.

•      All the air in a space as big as a house can be squeezed into a small tank.

•      On the other hand, air can expand almost indefinitely.

•      If all the air was removed from the inside of a house and then 1 cubic foot of air was supplied, the air would expand throughout the building.

•      Air also has weight.

•      And one way we can tell that air exists is by observing some of the things it does.  

For example, air can fill a balloon, and when it’s in the form of wind, it can move leaves and blow our hair around.

Let us understand with the help of an experiment: