Maharashtra Board Class 5 EVS Part I Chapter 16 Water PDF Download

16. Water

Can You Recall?

1. What happens when a spoonful of sugar, sawdust and soil are added to a glass of water?

2. Which are the three states of water?

3. What is done to make drinking water clean and safe?

Pollution Of Water

While it is raining, collect some of the rainwater directly in a clean container placed in the open. Also collect some of the rainwater that is flowing over the ground. Observe and compare the two.

What difference do you see? What is the reason for that?

When other substances get mixed with water, it becomes impure. Some of these substances float in the water. So, the water looks unclean or muddy. Some substances dissolve in the water and we cannot see them. If the substances that have got mixed with the water are harmful for living things, we say that the water has become polluted. Rivers, lakes are our sources of water. How does their water get polluted?

Teacher's Note

Water pollution happens when dirty things mix in our water. In India, many rivers like the Ganges have pollution problems because factories and cities dump waste into them.

Exam Trick

Remember: Polluted water = water with harmful things mixed in it. Just like when you mix dirt in milk, the milk becomes bad. Same thing happens to water.

Points to Remember

Pollution happens when bad substances mix with water.
Some substances float in water and make it muddy.
Some substances dissolve and we cannot see them.
Rivers and lakes get polluted from waste water.
Polluted water cannot be used for drinking.

Disposal Of Waste Water

The waste water of a city or town is collected and let into a water body at a convenient location. The waste water from residential buildings as well as from factories and industries contains many kinds of impurities. Some of these dissolve in the water while some do not.

Sewage water can carry microorganisms that spread diseases. Waste water from industries is more likely to contain poisonous substances. If all this waste water is let into water bodies as it is, the water bodies become polluted and that is dangerous. Such water cannot be used for drinking or for any other purposes. That is why, it is compulsory for factory-owners to treat the water before letting it out. Similarly, sewage and other waste water of towns and cities is processed for purification before letting it into a water body. This helps to prevent pollution of water.

Flowing water of rivers gets purified to some extent by natural processes also. Before water is supplied to a town or city, it is purified.

Teacher's Note

Factories must clean their waste water before releasing it. In India, the government has strict rules about this because our rivers are very important to us.

Exam Trick

Remember: Factories must treat waste water. Think of it like this - if you have dirty clothes, you wash them before wearing them. Same thing with factory waste water!

Points to Remember

Waste water comes from homes and factories.
Sewage water can carry harmful germs and diseases.
Factory waste can contain poisonous substances.
All waste water must be cleaned before entering rivers and lakes.
Rivers clean themselves naturally but also need our help.

Can You Tell?

List the substances that are mixed in the waste water drained out of the kitchen and bathroom in your house.

Purification Of Water

Take a plastic bottle. Tie a clean piece of cloth over its mouth. Cut off the base of the bottle. Hold the bottle upside down. Pour some powdered coal into it. Then add fine sand, and, lastly, coarse sand to make three different layers inside the bottle as shown in the diagram.

Place the bottle on its lower cut off portion as shown in the figure. Now, pour some muddy water containing some rubbish, slowly into this bottle.

Observe the water that flows into the base of the bottle. It appears clean. Of course, you have learnt that there could be micro-organisms in it.

Do You Know?

If large quantities of impurities get mixed with river water, the natural process of purification cannot keep pace. The proportion of oxygen dissolved in the water is reduced. And this is a threat to the aquatic living things.

Teacher's Note

We can clean water at home using sand and coal. This is a simple method that shows how water-works clean our drinking water in real life.

Exam Trick

Remember the layers from top to bottom: Powdered coal, fine sand, coarse sand. Think of it as a filter that catches dirt and makes water clean.

Points to Remember

Filtration removes visible dirt and particles from water.
Sand and coal help filter out impurities.
Cloth acts as the first barrier for large particles.
Filtered water may still have germs in it.
We need more steps to make water completely safe.

Do You Know?

While travelling, we often buy bottled drinking water. The bottles are available at places like bus stands and railway stations. Read the information about the water given on the bottle and tell others about it, too.

The date of bottling and the period for which the water can be safely used is printed on the bottle. It is important to read this information when buying a bottle. Once you have opened it, the water should not be kept for very long. The empty bottle must be crushed and thrown into a garbage bin, so that it cannot be reused.

Teacher's Note

Always check the date on bottled water before drinking it. In India, many people carry bottled water when they travel, so we must use it wisely and recycle the bottles.

Exam Trick

Remember: Check the date on bottled water just like you check the expiry date on milk at home. After opening, finish it quickly and crush the bottle before throwing it away.

Points to Remember

Read the bottling date before buying water.
Check how long the water is safe to drink.
Do not keep opened water bottles for too long.
Always crush empty bottles before throwing them away.
Empty bottles should not be reused.

This is a preview of the first 3 pages. To get the complete book, click below.