Water
A. Choose the correct option.
1. The salinity of water is higher in the
a. Mediterranean sea. [ ]
b. Red sea. [ ]
c. Dead sea. [✓]
d. Caribbean sea. [ ]
2. Which of the following is not a cause of water pollution?
a. Petroleum slicks. [ ]
b. Excessive rain. [✓]
c. Industrial waste. [ ]
d. Domestic sewage. [ ]
3. The purest form of natural water is
a. rainwater. [✓]
b. sea water. [ ]
c. spring water. [ ]
d. lake water. [ ]
4. In the solution of chalk powder and water, chalk powder is a
a. solute. [✓]
b. soluble substance. [ ]
c. solvent. [ ]
d. none of these. [ ]
5. Which of the following diseases is not caused by domestic sewage?
a. Jaundice. [ ]
b. Diarrhoea. [ ]
c. Typhoid. [ ]
d. Malaria. [✓]
6. Which of the following is not the correct measure to conserve water?
a. Drip irrigation. [ ]
b. Over-watering of plants. [✓]
c. Afforestation. [ ]
d. Rain water harvesting. [ ]
B. State whether True or False (T/F).
1. The underground water is free from dissolved salts of calcium and magnesium. [F]
2. Alcohol dissolved in water is an example of aqueous solution. [T]
3. Carbonated water is an example of unsaturated solution. [F]
4. Polluted water is unfit for bathing, drinking or agricultural use. [T]
5. Chemicals such as fertilisers, insecticides, pesticides and weedicides decrease agricultural production. [T]
C. Fill in the blanks.
1. Surface water and underground water are the two main sources of water.
2. Marine life is not possible in Dead sea.
3. Solution of milk in water is an aqueous solution.
4. The level of underground water under the Earth's surface is called water table.
5. Water helps in the germination of seeds.
6. Construction of dams and reservoirs helps to control flood.
D. Give one word for the following.
1. Planting of trees.
= Afforestation.
2. The reservoir of water above the impervious rocks below the Earth's surface.
= Underground water.
3. Solution that contains more solute than that could be dissolved by the solvent under normal conditions.
= Supersaturated Solution.
4. Springs that contain large amount of dissolved sodium carbonate.
= Soda Springs.
5. Substances that do not dissolve in water.
= Insoluble Substance.
6. Prevention of water pollution and water wastage.
= Conservation of water.
E. Short answer type questions.
1. What is surface water? Name its types.
= The water present on the surface of the Earth is called surface water.
Surface water is divided into three types -
i) Rain water;
ii) River and lake water;
iii) Sea and Ocean water;
2. Define solution. When a solution is said to be saturated?
= A homogeneous mixture of one or more substances(the solute) dissolved in another substance(the solvent) is called a solution.
A solution is said to be saturated when no more solute can be dissolved in it at a particular temperature.
3. Why is conservation of water important?
= Water needs to be conserved in order to make it easily available for future generations.
4. Differentiate between soluble and insoluble substances.
=
|
Soluble Substances |
Insoluble Substances |
|---|---|
|
1. These substances dissolve in water. |
1. These substances do not dissolve in water. |
|
2. Example:- Salt, Sugar etc. |
2. Example:- Sand, Sawdust etc. |
5. Name the causes of water pollution.
= The causes of water pollution are -
i) Domestic Sewage; ii) Agricultural waste; iii) Industrial waste; and iv) Petroleum spills.
6. Why water is called universal solvent?
= Since water has a capacity to dissolve large number of salts in it, it is called a universal solvent.
F. Long answer type questions.
1. Explain the uses of water.
= Water is one of the most important substances on the Earth. All plants and animals must have water to survive. Apart from drinking, there are many other uses of water.
i) Sustenance of life:- All living things on the Earth depend on water for their survival and growth. Water is essential for digestion, assimilation and excretion in living things.
ii)At homes:- Water is used for many household purposes such as cooking, drinking, bathing, flushing toilets, and washing clothes and utensils.
iii) Plants and animals:- Plants use water for photosynthesis. Water also helps in germination and dispersal of seeds and fruits. A large quantity of water is used to irrigate crops.
iv) Industries:- In industries, water is used as a raw material, coolant, transport and source of energy.
v) Electricity:- The energy of flowing water is converted into electricity in hydroelectric power station.
vi) Transportation:- Goods and people are transported by different waterways.
vii) Recreation:- Lakes, rivers and streams are used for different water sport facilities such as boating, swimming, water polo and skiing.
2. What is water pollution? How can it be controlled?
= Water is said to be polluted if it contains harmful substances(impurities) that make it unfit for drinking, bathing or agricultural use.
Water pollution can be controlled by the following measures -
i) Excessive use of fertilisers, insecticides and pesticides should be avoided. Compost and organic pesticides should be used.
ii) Water in lakes, rivers and ponds should be cleaned periodically.
iii) Trees and shrubs should be planted along the banks of the rivers.
iv) Use of the biodegradable detergents should be encouraged instead of synthetic detergents.
v) Household garbage should not be thrown into rivers and lakes.
3. What are the ways of conserving water?
= Water can be conserved by the following ways -
At the personal level:-
i) Close taps when not in use.
ii) Repair leaking taps and pipes at the earliest.
iii) Use bucket and mug for a bath instead of using the shower.
iv) Water garden plants in the evening.
v) Plant trees.
vi) Install rainwater harvesting system in your home.
At the national level:-
i) Planting of trees(afforestation) should be encouraged in a large scale.
ii) Dams and reservoirs should be constructed in order to control floods and store water for future use.
iii) The use of biodegradable fertilisers should be encouraged in place of chemical fertilisers.
iv) Rainwater harvesting should be encouraged.
v) Water recycling practices should be encouraged in industries.
G. Challenge Questions.
1. Sewage should not be disposed of in rivers or oceans before treatment. Why?
= The pollutants present in the sewage water make it unfit for drinking and also harm the aquatic life. Mercury poisoning leads to Minamata disease. Hot water poured into water bodies cause thermal pollution killing aquatic organisms.
2. Drinking much water does not prevent our skin from drying. Why?
= The moisture level of skin is not determined or affected by the amount of water we drink. Instead, there are some external factors such as skin cleansing, the environment, the number of oil glands and the functioning of these oil glands, which determine the moisture level of the skin. Thus, consuming large quantities of water will not prevent dry skin.