Water is the most important natural resource given to us by nature. As soon as you hear the word “water”, you will think of rivers, streams, ponds, wells, etc. Water is commonly found in liquid state. Does water exist only in the state of liquid ? Let’s do the follwing activity to find it.

It can be observed that when ice cubes are heated, they turn into liquid water. When further heated, water turns into vapour. Hence water exists in three physical states as ice, liquid water and water vapour.

3.1 States of Water

Water exists in the states of solid, liquid and gas in the natural environment.

Water in Solid State

Ice, snow, glaziers are some examples for the solid state of water. Glaziers can be seen in the Southern and Northern poles of the world. In some countries, snow can be seen in the winter season. Snow is also a solid state of water.

Water in Liquid State

The liquid state of water can be seen in lakes, streams, rivers, tanks, ponds, wells and seas. The word “water” in our language normally refers to water in liquid state.

Fig. 3.4 Water in liquid state

Water in Gaseous State (water vapour)

Steam and water vapour are examples for the gaseous state of water. Water exists in the atmosphere as water vapour. Let’s do the following activity to find out whether there is water vapour in the atmosphere.

Water vapour in the atmosphere condenses and can be seen on the outer surface of the glass. Hence, there is water vapour in the atmosphere.

3.2 Types of Water Based on Availability

What happens to the rain drops when they fall on to earth? Sometimes they flow, sometimes they are absorbed by the soil and sometimes they gather in muddy puddles. Let’s do the following activity to find out what happens to the rain drops when they fall on to earth.

The water comes through the tin and falls on soil is called precipitation/ rain. The water which flows through the components of soil is called ground water and the water remaining on soil is called surface water.

Accordingly, precipitation / rain, ground water and surface water are the ways in which water exists.

Precipitation

The types of precipitation are rain, snow, hail, sleet etc.

Surface water

The types of surface water are oceans, seas, rivers, streams, tanks, ponds, lakes, waterfalls.

Ground water

The water in wells and springs are the types of ground water.

3.3 Types of Water Based on Salinity

Why does sea water taste salty ? Dissolution of different things in water is a special property of water. Many things are dissolved in sea water. Sodium chloride is a one type of salt dissolved in sea water. This is the reason for sea water to taste salty. Based on salinity, water can be further categorized as fresh water, marine water and brackish water.

Fig. 3.7 Classification of water according to salinity

Here, water without salt can be assumed as fresh water, 2 g of salt dissolved water as brackish water and 6 g of salt dissoved water as marine water. You can observe that the water with more dissolved salt has higher mass. Accordingly, when the mass of an equal volume is considered, it can be concluded that the mass of water is high with salinity. Based on this, we can separately identify fresh water, marine water and brackish water.

3.4 Importance of Water

Importance of Water for Human Activities

Water is very important not only for the existence of life but also for many human activities.Think how many times you use water for different activities during the day.

Categorise your findings in Assignment 3.2 under the following headlines.

1. For industries including agriculture

2. For sanitary purposes

3. For household activities

4. For transportation

5. For leisure

6. For water related sports

7. To generate electricity

Importance of Water for the Existence of Life

A person who is suffering from diarrhea has a risk of facing dehydration, may even face death. Also, if a plant doesn’t get sufficient water, it gets withered. So, you can now understand that water is a very essential factor for the existence of living beings.

The following figure shows how water is important for life.

3.5 Water, a Limited Resource

There are many gifts of nature. They are called natural resources. Water is a very important gift of nature. But it is a limited natural resource. The reason is most of the sources of water are not in a condition to use directly.

Water covers more than 70% of the earth surface but the percentage of water that can be consumed is 0.01%.

Even though water is a natural resource, most of the people use it in a very careless manner. Think about the amount of water you waste daily.

Water Pollution

There are some water bodies with different types of waste materials, bad smell and de-colourization. Addition of waste materials to water till it becomes unsuitable for consumption is known as water pollution. Even though there is only about 0.01% of water suitable for consumption, due to unawareness and carelessness of people, this limited amount of water is getting polluted.

The following figure shows some methods of water pollution.

Fig. 3.11 Some methods of water pollution

Pollution of surface water affects ground water too. The poisonous chemicals in surface water are added to the ground water too. As ground water is used to drink, these poisonous chemicals enter the human body. This causes many serious illnesses such as cancers, kidney failures, etc.

Precautions should be taken as soon as possible to prevent water pollution. Otherwise, we will also lose the limited amount of water that is suitable for consumption.Taking necessary steps to stop water pollution is a timely need.