Grade-3 Science, Term-2 Chapter-4 Water as a Resource

Chapter - 4

Topic:  Water as a Resource

Water is found in different forms. Match these:

A	B
Vapour and clouds	Mountain ranges
Waves and ice- bergs	Sky
Glaciers	Solid/Liquid/Gas
Ice/Water/ Water vapour	Sea

Ans-

A	B
Vapour and clouds	Sky
Waves and ice- bergs	Sea
Glaciers	Mountain ranges
Ice/Water/Water vapour	Solid/Liquid/Gas

Fill in the blanks with suitable word: 

(heated, impurities, three-fourth, rain, cooling)

     1.    We can change the state of water by either heating or cooling it.

     2.    When ice is heated, it forms water.

     3.    Rain is the purest form of water.

     4.    Three-fourth of the Earth is covered with water.

     5.    Substances that make water impure are called impurities.

 State whether the following statements are true or false:

    1.    We get steam on heating water. True

    2.    Water is found in river, ponds and lakes. True

    3.    Impure water is harmful for both plants and animals. True

    4.    Water has a definite shape. False

    5.    Heating decreases the rate of mixing in a water solution. False

Give one word for the following:

1-  The process by which water is changed into steam on heating. Evaporation

2-  The process in which steam is cooled to form water.

Condensation

3-  The process by which water is changed to ice by cooling.

Freezing

4-  When ice changes to water, it is called _____

Melting

5-  Process in nature, in which we see inter-convertible nature of water. Water Cycle

6-  Substances that male water impure. Impurities

7-  Technique for collecting, storing and using rainwater for landscape, irrigation and other uses.  Rainwater Harvesting  

Answer these questions:

         Q1.     What is water cycle?

Ans-  Water cycle is the continuous movement of water (in its interconvertible forms) above or below the surface of earth.

          Q2.     Write any two properties of water.

Ans- Following are two properties of water:

a.    Water is colourless

b.    Water is odourless

         Q3.     What is rainwater harvesting?

Ans-  Rainwater harvesting is a technique used for collecting, storing and using rainwater for landscape, irrigation and other uses.

         Q4.     What are the benefits of rainwater harvesting?

Ans- Following are the benefits of rainwater harvesting:

1-Reduces water shortage in rural areas.

2-Suffice water requirement in homes and industries.

3-  Provides ample water for landscape.

4-Easy and low-cost water supply in areas with water scarcity.

         Q5.     What are soluble and insoluble impurities. Give examples.

Ans- Soluble Impurities- Impurities which dissolve in water and cannot be seen are called as soluble impurities. Example: Germs

Insoluble Impurities- Impurities which do not dissolve in water and can be seen are called as insoluble impurities. Example: Sand, clay

Q6.     Write short note on:

(a) Filtration of water using layers of cloth

(b) Chlorination of water

(c)  Boiling

Ans- Filtration of water using layers of cloth - A cloth is folded at least four times and secured at the opening of vessel for filtering of water. This is an easy and inexpensive method.

Chlorination of water – 4 drops of bleach is added in a litre of water and allowed to stand for at least an hour.

Boiling- In this method water is boiled vigorously for at least one minute. Boiled water can be used for drinking after cooling.

Q7.     Boiling is the most referred method of water purification. Why?

Ans- Boiling is the most preferred method of purification of water because disease causing germs cannot survive boiling heat.

     Q8.     Water exerts push. Explain with example.

Ans- Water pushes anything that obstructs its path while flowing. For example: water can move the sand on the beach.

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