Water — Practice

Question 1

What is the original source of all fresh water on Earth?

Accepted Answer

Rain. Every well, river, lake and pond is filled by rain, directly or indirectly.

Question 2

What does potable mean, and name three ways of making water potable.

Accepted Answer

Potable means safe to drink: clean, free of germs and free of harmful chemicals. Boiling, filtering and chlorination all help.

Question 3

Which is the largest source of water on Earth, and can it be drunk?

Accepted Answer

The sea. It cannot be drunk, because it is salt water.

Question 4

Roughly what fraction of the Earth's water is fresh, and why does that matter?

Accepted Answer

About three parts in every hundred, and much of even that is frozen or deep underground. So very little is actually available for drinking, cooking and farming, which is why saving water matters even where it rains.

Question 5

Give three ways to save water at home.

Accepted Answer

Turn the tap off when the bucket is full rather than letting it overflow, wash fruit and vegetables in a bowl instead of under a running tap, and turn the tap off while brushing your teeth. Mending a dripping tap also helps.

Question 6

Give two ways to look after a village pond or lake.

Accepted Answer

Deepen it so it holds more water through the dry season, and plant trees on the banks so their roots hold the soil and less of it washes in. Keeping rubbish out is a third.

Question 7

A classmate says sea water can be made drinkable simply by boiling it. Explain why this fails.

Accepted Answer

Boiling kills germs but does not remove dissolved salt. As steam leaves, the salt stays behind, so the remaining water actually becomes saltier. Removing salt needs a different process altogether.

Question 8

Why is washing a vehicle with a running hose worse than using a bucket, and why does plastic in a river cause harm for so long?

Accepted Answer

A running hose can use many times the water a bucket needs for the same wash, so most of it runs away unused. Plastic lasts for hundreds of years, so it keeps polluting the water, harming fish and blocking channels long after it was thrown in.

Practice — Water

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