Class 7 Science Chapter 16 Important Questions
Class 7 Science Chapter 16 Important Questions Answers of Water: A Precious Resource updated for academic session 2020-2021. All the important extra questions are taken from the latest NCERT book issued for session 2020-2021.These extra practice questions with answers are helpful for the preparation of school test and terminal exams. All the topics are completely covered through class 7 science extra questions.
Class 7 Science Chapter 16 Extra Questions for 2020-2021
|Chapter: 16||Water: A Precious Resource|
|Contents:||Important Extra Question Answers|
Class 7 Science Chapter 16 Important Questions Set – 1
What do you mean by “World Water Day”?
22 March is celebrated as the world water day. The amount of water recommended by the United Nations for drinking, washing, cooking and maintaining proper hygiene is a minimum of 50 liters per person per day. This amount is about two and a half buckets of water per person per day. Millions of people in our country do not get sufficient water they usually walk several kilometers daily with pitchers on their heads to fetch water for their households. We celebrate water day every year (22th march) to attract the attention of everybody towards the importance of conserving water.
Why water is so important for us?
Water is one of the most common and useful substances around us. Water is essential for the existence of life. All the living things (including human beings, animals and plants) need water to live. Water carries nutrients to all cells in our body and oxygen to our brain. Water allows the body to absorb and assimilate minerals, vitamins, amino acids, glucose and other substances. Water flushes out toxins and waste. Water helps to regulate body temperature. Without water there would be no living things on the earth.
Write down the forms of water or states of water.
Water exists in three forms as solid, liquid and gas. When water circulates in nature through the water cycle, it can be found in all the three forms. When water circulates through the water cycle it can be found in all the three forms, i.e., solid, liquid and gas—at any given time somewhere on the earth. The solid form, snow and ice, is present as ice caps at the poles of the earth, snow-covered mountains and glaciers. Liquid water is present in oceans, lakes, rivers, and even underground. The gaseous form is the water vapor present in the air around us. The continuous cycling of water among its three forms keeps the total amount of water on the earth constant even when the whole world is using it.
Explain how the water is wasted at individual level.
There are various reasons of wastage of water at individual level. All of us waste water while brushing teeth, shaving, bathing, washing and during various other activities. Leaking taps are also big source of huge water wastage. We generally leave the taps running at public places. This habit makes use lots of potable water.
Write short note on “scarcity of water” or “shortage of water”.
All of us need water every day for drinking, cooking food, washing, brushing teeth, bathing and flushing toilets and for etc. work. UN recommended the amount of water for per person is 50 liters per day. Millions of people in our country do not get sufficient water in some place. There is an acute shortage of water especially during summers. In this case women and children usually walk several kilometers daily with pitchers on their heads to fetch water for their households. This harms the woman as well as children life. The village children suffer because they spend hours in fetching water due to which they cannot attend their school regularly. In fact, water shortage has become a matter of concern throughout the world. It is estimated that in a few years from now more than one third of the people in the world could face water shortage.
Class 7 Science Chapter 16 Important Questions Set – 2
What is the meaning of shortage of water?
The amount of water recommended by the United Nation for various uses of a person per day is 50 liters. Millions of people in our country do not get enough water to fulfill minimum requirement. This means shortage of water.
There are ten tube-wells in a lane of 50 houses. What could be the long-term impact on the water table?
The effect on the water table depends on the replenishment of underground water. Only five families will share a tube well. So, the water used for daily domestic purposes will not affect the water table. But if there is no shortage of rain, the water used by the families will not be replenished and water table will fall down.
Write down the relation between water table and groundwater.
If we dig a hole in the ground and dig deeper and deeper, we could reach a level where all the spaces between particles of soil and gaps between rocks are filled with water. The upper limit of this layer is called the water table. The water found below the water table is called groundwater.
How does people of Rajasthan overcome the challenge of erratic rain fall?
Rajasthan is a hot and dry place which gets erratic rainfall. The challenge of natural scarcity of water has been successfully overcome by the collective actions of the people. A number of social workers have revived five dried up rivers Arveri, Sarsa, Bhagani, Ruparel, Jahaz-wali, by constructing rainwater harvesting structures. The increased water available has transformed a dry area in the “Alwar district of Rajasthan” into a lush green area.
How much water is available on the earth? Show an activity.
About 71% of the Earth’s surface is covered with water. The total water present on the earth about 97.4 percent is in the seas and oceans. The water which is fit for use by human beings is called freshwater. Only 2.6 % of the total water on the earth is the freshwater. Almost all the water on the earth is contained in the seas and oceans, rivers, lakes, ice caps, as groundwater and in the atmosphere. However, most of this water is not fit for human consumption. Perform the following activity to estimate roughly the relative amount of water available in some of these sources.
Take a medium-sized bucket and fill it up with water. It contains about twenty liters of water. Assume that this water represents all the water present on the earth. Take a tea spoon of about 5 mL capacity and transfer 100 spoons of water from the bucket to a small container, like a bath mug. This represents total freshwater on the earth. From the bath mug transfer thirty spoons of water to a glass tumbler. This gives a measure of usable water present as ground- water. Finally take out a quarter (1/4th) spoonful of water from the mug. It represents all the water present in all the lakes and rivers of the world. The water left in the bucket represents the saline water present in the seas, oceans and partly as groundwater. This water is not fit for human use. The water left in the bath mug represents the water, which is present in the frozen form in glaciers, ice caps and permanent snow; again, not available readily.
Class 7 Science Chapter 16 Important Questions Set – 3
Explain, how groundwater is recharged?
The rain water and water from other sources such as rivers and ponds seeps through the soil and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called infiltration. By the process of infiltration, groundwater recharged.
You have been asked to maintain a garden. How will you minimize the use of water?
Drip irrigation and sprinkler system can be used in the garden to minimize the use of water. Watering to plants should be done to minimize loss of water by evaporation.
What do you mean by “water cycle”?
The sun heats up the water of oceans, ponds and rivers due to which water evaporates. These water vapors being lighter are carried up by the air. These water vapor get cooled at height and water droplets are formed. These water droplets form a cloud. When these water droplets in a cloud come close together, they form drop of water. These drops of water may fall on the earth as rain. The rain water is absorbed by the soil. A part of rain water collected in the rivers flows into the sea, where again the evaporation occurs. This completes the water cycle.
Write down the exact reason for the shortage of water.
The main reason for the shortage of water or scarcity of water are increasing population, growing irrigation requirements of agriculture, rapid growth of industries and mismanagement of water.
“The main source of groundwater is the rain”. Discuss.
The rain water and water from other sources such as rivers, lakes and ponds etc., seeps through the ground and fills the empty spaces between the soil and the rocks below the earth. The water keeps on seeping deeper and deeper into the ground through the soil and permeable rocks until it reaches an impermeable rock or hard rock.
So, water starts collecting above the impermeable rock and fills the soil and permeable rocks completely with water up to the level known as water table. The underground layer of soil and permeable rocks in which water collects under the ground is called an “aquifer”. The top of aquifer is referred to as “water table”. Aquifer stores and provides ground water. The rainwater which seeps into the ground ultimately reaches the aquifer and gets stored there.
We take out groundwater for our use with the help of wells, tube wells and handpumps. This decreases the amount of groundwater. But when it rains, the rain water seeps into the ground and the groundwater is recharged.
Class 7 Science Chapter 16 Important Questions Set – 4
Do you have any idea about proper management of water?
We have seen that most of the water that we get as rainfall just flows away. This is a waste of precious natural resource. The rainwater can be used to recharge the groundwater. This is referred to as water harvesting or rainwater harvesting. We have at many places in India an age-old practice of water storage and water recharge like the bawris. Bawri was the traditional way of collecting water. With time the bawris fell into disuse and garbage started piling in these reservoirs. However, because of the acute water shortage, people in these areas have had to rethink. The bawris are being revived.
Today, the situation is that inspite of scanty rains these places are managing their water needs well. A farmer using water in the field can also use water economically. Maybe you have heard of drip irrigation. Drip irrigation is a technique of watering plants by making use of narrow tubings which deliver water directly at the base of the plant.
What do you think about the effect of water scarcity on plants?
The scarcity of water will affect the nutrient uptake by the plants and the process of food making photosynthesis in plant. So, due to scarcity of water, the plants will not be able to make sufficient food for themselves and for animals.
Due to decrease photosynthesis caused by the scarcity of water, the plants will not be able to release sufficient oxygen into the air. Plants help in bringing rain by releasing a lot of water vapor into the atmosphere through transpiration. Scarcity of water for plants will reduce transpiration.
We can say that the effects of scarcity of water on plants as shortage of food, shortage of oxygen for breathing and lesser rainfall. This may lead of the end of all life on the earth. In the absence of plants, there will be no food for anyone to eat, no oxygen to breathe, and no enough rainwater.
What is groundwater? What are the sources of water which are fed by groundwater?
Water below the water table where water is found between particles of soil and between rocks is called groundwater. Water table is the upper level of water under the ground which occupies all the spaces in the soil and rocks. The groundwater provide water to wells, bawris, tube wells, hand pumps.
Explain the reason behind the depletion of water table.
There are some of the factors which affect water table, at a place and make it go down as increasing populations, industrial and agricultural activities, scanty rainfall, deforestation and decrease in the effective area for seepage of rainwater.
- i) Increasing population needs more and more water for its day-to-day activities. So, due to increasing population, on the other hand we are consuming more groundwater and we are allowing less rain water to seep into the ground. This leads to the depletion of water table.
- ii) Industries produce a large number of various types of things which we use in our everyday life. As the population is increasing the demand for various industrial goods is increasing, and hence the number of industries is also increasing continuously. As a number of industries is increasing, the water drawn from the ground for their use is also increasing.
- iii) The growing of various crops in agriculture requires a lot of water for irrigation. In India, a majority of farmers depend on rains for irrigating their crops. As more and more food has to be grown for increasing population, the use of groundwater for agriculture is increasing day by day.
- iv) Sometimes there is scanty rainfall during the rainy seasons. In such a situation, much more ground water is drawn out by the people for various purposes. This leads to the depletion of water table.
- v) Deforestation is the cutting down of trees and plants from the forest for various purposes. We know that forests help in bringing rain. So lesser number of trees and plants in the forest will bring less rainfall. If there are lesser number of trees and plants in the forest, less rain water will seep into the ground. This depletes the water table.
- vi) Due to increasing urbanization and industrialization more and more space is being covered by houses, buildings, roads etc., and the open spaces having unpaved ground are getting reduced day by day. This leads to the depletion of water table.
Write short notes on “mismanagement of water”.
We are living in an area where there is sufficient rainfall but it may be possible, yet there is shortage of water. This can happen, if there is mismanagement of water resources.
- At many places water is supplied through a well-planned network of big and small pipes. Many times, we have seen the big water supply pipes leaking and a lot of water gushing out of these pipes. The leaking pipes lead to the wastage of precious water.
- All of us knowingly or unknowingly waste a lot of water while brushing teeth, shaving, bathing, washing clothes, washing utensils, watering the plants and during many other activities. Leaking taps in our houses are another source of huge water wastage.
- Most of the rain water which falls around us during rainy season just flows away into dirty water drains and becomes useless. This is the wastage of precious natural resource of water. The concerned Government Department as well as the public are responsible for the mismanagement and wastage of this rainwater. This is because rain water can be used to recharge groundwater for future use.
Class 7 Science Chapter 16 Important Questions Set – 5
What do you mean by Deforestation?
Deforestation is the cutting down of trees and plants from the forest for various purposes. We know that forests help in bringing rain. So, lesser number of trees and plants in the forest will bring less rainfall. So, deforestation leads to lesser rainfall as well as lesser seepage of rainwater into the ground. If there are lesser number of trees and plants in the forest, less rain water will seep into the ground. This depletes the water table.
What do you mean by “Drip irrigation”?
Drip irrigation, the proper management of water in agriculture can be done by using the “drip irrigation” technique. Drip irrigation is a technique of watering plants by making use of a system of narrow pipes or tubes with a small hole, which deliver water directly at the base of the plants. Drip irrigation gives water directly to the roots of plants at a slow rate, so that it can be absorbed by the soil without any wastage. Drip irrigation, minimize the use of water in agriculture. A farmer using water in the fields can use water economically by making use of the drip irrigation technique.
Explain how increasing population is responsible for the depletion of water table.
Increasing population creates demands for construction of houses, shops, offices, roads and pavements. This decreases the open areas like parks and playgrounds. This in turn decreases the seepage of rainwater into the ground.
Moreover, a huge amount of water is required for construction work and daily chores, often groundwater is used for this purpose. So, on the one hand we are consuming more groundwater and on the other we are allowing lesser water to seep into the ground. This results in depletion of water table. In fact, the water table in some parts of many cities has gone down to alarmingly low levels.
Water is very precious for all the living being. What will happen in future, if we do not save water now?
Water is needed for various life activities. If we continue the misuse of water and do not conserve it, the groundwater level will be depleted. This may result into various consequences like:
- i) Lowering of the water table, excessive pumping can lower the groundwater table.
- ii) Reduce surface water supply, groundwater and surface water are connected. When groundwater is over used, the lakes, streams and rivers connected to ground water, can also have little supply.
- iii) Loss of plants from land, we fully dependent on the plants for food directly or indirectly. Plants, need water to prepare their food. If there will be scarcity of water on earth, the plant will be unable to prepare their food. This in-turn will lead to the end of the life because world without plants means no food, no oxygen, not enough rain and other innumerable problems. Therefore, it is true that water is a precious resource.
What is your role to minimize the wastage of water?
We can save water at home by minimizing its wastage in the following manner:
- Mop the floor instead of washing it daily.
- Do not use a full flush from the cistern in the toilet when a half flush is sufficient.
- Use the water from washing rice, vegetables or fruits for watering the plants at home.
- Take bath by filling water in a bucket and not directly under the following tap. Wash the utensil by filling water in a basin and not under the running tap.
- Do not keep the tap running all the time while brushing the teeth.
- And one of the most imported, get the leaking taps repaired immediately because leaking taps waste a lot of water.