Class-6 Science, Chapter-14 Water, Additional exercises with solutions in line with NCERT book / CBSE Syllabus


Chapter 14
Water
=========================================================
Exercises from textbook
Additional Exercises
Tables from Textbook
Activities/Projects
Additional Exercises
Choose the correct answer:

1-    More and more water is being used for
a.    Industries
b.    Agriculture
c.    Domestic purposes
d.    All the above (√)
2-    ‘Çatch water where it falls’ is the basic idea behind
a.    Draught
b.    Flood
c.    Rainwater harvesting (√)
d.    Transpiration
3-    The release of water by plants into the atmosphere occurs through a process called
a.    Evaporation
b.    Transpiration (√)
c.    Vaporization
d.    None of the above
4-    The rainwater that seeps into the soil is recharges
a.    Ground water (√)
b.    Rainwater
c.    Floodwater
d.    Distilled water
5-    Excessive rains may cause
a.    Draught
b.    Flood (√)
c.    Evaporation
d.    All the above
6-    Lack of water for long periods may cause
a.    Draught (√)
b.    Flood
c.    Evaporation
d.    All the above
7-    Many tiny droplets of water come together and fall down as
a.    Rain
b.    Hail
c.    Snow
d.    All the above (√)
Fill in the blanks with suitable words:
1-    Two third of the Earth is covered with water.
2-    The sea water is saline.
3-    Heating is essential to convert water into its vapours.
4-    Tiny droplets of water that remain floating in air , appear to us as cloud.
5-    Sowing of many crops depends on the arrival of monsoon.
6-    Draught happens if it doesn’t rain in a region for a year or two.

State whether the following statements are True or False:
1-    To obtain salt, water from the sea is left in shallow pits to let the water evaporate.True
2-    There has been a loss of ground water due to overuse. True
3-    In our country, most of the rainfall occurs during the monsoon season. True
4-    Floods cause extensive damage to crops, domestic animals, property and human life. True
5-    Water present in oceans can be used directly. False
6-    The number of people using water is decreasing with rising population. False

Give one word for the following:
1-    The process through which water vapour gets transferred into air.
2-    Ans- Evaporation
3-    The process through which water is released by the plants into air.
4-    Ans- Transpiration
5-    The circulation of water between oceans and land
6-    Ans- Water Cycle
7-     

Answer these questions:

Q. Mention some uses of water.
Ans- Some of the uses of water are as follows:
Cooking
Cleaning utensils
Washing Clothes
Bathing
Irrigation of crops
Production in industries

Q. Name some sources of water.
Ans- Following are some sources of water:
(1) River
(2) Spring
(3) Pond
(4) Well
(5) Hand pump
(6) Lake

Q. We need water not only for our daily activities but also for producing many things. Explain.
Ans- We use rice, pulses, vegetables food items everyday. Fibre for making fabric comes from plants. Water is needed to grow them.
Water is used in industries for producing almost all the things that we use.


Q. Imagine a day in your life when water supply through taps is not available. What will you do to meet the needs of water?
Ans- If water supply through taps is not available to us for a day, we will have to fetch water ourselves from a far away place. We will use less amount of water that day.

Q. Why is the seawater not fit for drinking and other domestic, agricultural and industrial needs?
Ans- The seawater has many salts dissolved in it- the water is saline. So, it is not fit for drinking and other domestic, agricultural and industrial needs.

Q. How is salt obtained from seawater?
Ans- To obtain salt water from the sea is left in shallow pits to let the water evaporate. Salt is left behind in this process.

Q. How does it rain?
Ans- Droplets of water remain floating in the air and appear to us as clouds. It so happens that many droplets of water come together to form large sized drops of water. Some drops of water become so heavy that they begin to fall. These falling water drops are called rain.

Q. Mention factors that are leading to shortage of water.
Ans- Following are the factors responsible for shortage of water.
1- Most of the water is in ocean and can not be used directly.
2- The level of ground water is decreasing with over usage.
3- With rising poulation, number of people using water is also increasing.
4- More and more water is being used for producing food and by industries.

Q. What do you understand by rainwater harvesting? Discuss the techniques of rainwater harvesting.
Ans- The basic idea behind rainwater harvesting is to catch water where it falls. In rainwater harvesting, water is collected and stored for later use.

Following are two techniques of rainwater harvesting:
1- Rooftop rainwater harvesting for use- Rainwater is collected in a storage tank from the rooftop through pipes. This water needs to be filtered before use.
2- Rooftop harvesting for groundwater recharge- Another way is to let water seep into the soil instead of collecting it in storage tanks. This method is used to recharge / refill ground water.
3- Ground water recharge through roadside drains- Rainwater in roadside drains is allowed to go into the ground directly.

Exercises from Textbook
Fill up the blanks in the following:
(a)  The process of changing of water into its vapour is called evaporation.
(b)  The process of changing water vapour into water is called condensation.
(c)   No rainfall for a year or more may lead to draught in that region.
(d)  Excessive rains may cause flood.
State for each of the following whether it is due to evaporation or condensation.
(a)  Water drop appears on the outer surface of a glass containing cold water.Condenastion
(b)  Steam rising from wet clothes while they are ironed. Evaporation
(c)   Fog appearing on a cold winter morning. Condensation
(d)  Blackboard dries up after wiping it. Evaporation
(e)  Steam rising from a hot griddle when water is sprinkled on it. Evaporation
Which of the following statements are true?
(a)  Water vapour is present in air only during the monsoon. False
(b)  Water evaporates into air from oceans, rivers, lakes but not from the soil. False
(c)   The process of water changing into its vapour, is called evaporation. True
(d)  The evaporation of water takes place only in sunlight. False
(e)  Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler. True
Suppose you want to dry your school uniform quickly, would spreading it near an aanghiti or heater help? If yes, how?
Yes, the anghiti or heater will heat up the surrounding air. This warm air provides heat for evaporation of water from school uniform.
Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
We notice a puddle of water around the cooled bottle of water. The water vapours present in the atmosphere get condensed near the surface of cooled water bottle and form a puddle after sometime.

To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
To clean the spectacles, people often breathe out on glasses. The air that we breathe out contains moisture. This moisture (water vapours) present in the exhaled air gets condensed on the surface of glasses.
How are clouds formed?
Water vapours continuously enter into the atmosphere through the processes of evaporation and transpiration.  At sufficient Heights, the air becomes so cold that the water vapour present in it condenses to form tiny drops of water called droplets. It is these tiny droplets that remain floating in air and appear to us as clouds.
When does a drought occur?
Drought occurs if it doesn't rain in a region for a year or more. The soil continues to lose water by evaporation and transpiration. Since it is not being brought back by rain, the soil becomes dry. The level of water in ponds and wells of the region goes down and some of them may even dry up. The ground water may also become scarce. This may lead to drought.

Tables from Textbook
Table 14.1 Estimation of amount of water used by a family in a day
(You may use a mug, a glass, a bucket or any other container to measure the amount of water used)
Activity
Amount of water used (in glasses)
Drinking
 15
Brushing
2
Bathing
60
Washing utensils
240
Washing clothes
450
Toilets
150
Cleaning floor
150
Any other (Cooking)
10
Total water used in a day by a family
1077 glasses

Suggested Projects and Activities
1-    List three activities in which you can save water. For each activity describe how would you do it.
2-    Collect pictures relating to floods or drought from old magazines or news pares. Paste them in your notebook and write about the problems that people would have faced.
3-    Prepare a poster on ways of saving water and display it on your school notice board.
4-    Write a few slogans of your own on the topic ‘Save Water’.



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