Page 77 - Active Science 5 Ebook and Activity

Let’s Recapitulate

Match the following.
1. Troposphere a. the highest layer of atmosphere
2. Stratosphere b. extreme low air pressure

3. Mesosphere c. lowest layer of atmosphere
4. Thermosphere d. coldest layer of atmosphere

5. Exosphere e. protects us from harmful ultraviolet radiation

Water
Water is the most abundant substance available on
the surface of earth. About three fourth (3/4 ) of the
th
earth’s surface is covered with water. In nature, it
is found in all the three states of matter – solid,
liquid and gas. It is found in oceans, rivers, lakes

and other water bodies.
River
Water is very essential for survival of life. We need
it for drinking, cooking, washing, cleaning, growing
plants, putting out fire and for many other purposes.
We also take water through drinks like fruit juice,

milk, tea or coffee. Water is also present in the food Well
we eat.

The main sources of water are rainwater, lakes,
rivers, wells, etc. Water from these sources is impure Lake

because these contain sand, germs, stones, etc.,
making it unfit for human beings. Water fit for human consumption is called potable
water.

Water has some impurities in it which can either be soluble or insoluble. Soluble impurities
dissolve in water whereas insoluble impurities do not dissolve in water.

Properties of Water

1. Water is an important constituent of all functions of the body.
2. It is a main constituent of blood.

3. Water can exist in all the three states of matter.

4. Solid water is less dense than the liquid state which causes ice to float on water.
5. Water is made up of two molecules of hydrogen and one molecule of oxygen.

6. The molecules in water bond together and give rise to buoyant forces that keep

things afloat in water.
77
Active Science-5