Chapter
7
Water,water
everywhere
Short
Questions
Q1. How much water we need to drink daily?
Ans: We need to drink about 2 litres of water daily.
Q2. : Define irrigation?
Ans: For the crops, formers bring water from rivers,
lakes and wells to their fields. Water is carried in pipes and ditches. This
special kind of watering is called irrigation.
Q3.: Define desalination?
Ans: Salt can be removed from sea water by a process
of distillation called desalination.
Q4. : What are reservoirs?
Ans: A reservoir is a large artificial lake made by
building a dam across a river. Wherever possible, reservoirs are built high up
in hills or mountains where they can be fed by clear rivers and streams.
Q5. : Write down the names of some oceans?
Ans:
i.
Atlantic ocean
ii.
Pacific ocean
iii.
Arctic ocean
iv.
Indian ocean
v.
Southern ocean
Q. 6: Write down the names of some water-borne
diseases?
Ans:
i.
Polio ii. Hepatitis iii. Typhoid iv. Diarrhoea v. Cholera
Q. 7: Why rivers and lakes called fresh water?
Ans: Because they do not contain salts in water like
sea so they are called fresh water.
Q. 8: Name some industrial uses of water?
Ans: Cement, concrete, steel , paper and petroleum are
some industrial uses of water.
Q. 9: What are glaciers?
Ans: These are mountains covered with ice called
glaciers. e.g., Himalayan glaciers.
Q. 10: What are biodegradable?
Ans: A substance which can be broken down by natural
process of decay is called biodegradable.
Q. 11: What is the worst water related disease?
Ans: One of the worst disease is bilharzia or
schistosomiasis.
Q. 12: What is sewage?
Ans: Sewage is the waste water from houses colleges
and factories. It contains faeces, urine, paper, detergents and waste chemicals
dissolved in water.
Long
Questions:
Q1: Explain the steps
of water treatment?
Following are the steps
involved in water treatment.
1.
Coagulation:
At
the treatment plant, the raw water is mixed with alum (aluminium sulphate) and
lime. They make tiny suspended particles of clay stick together.
2.
Sedimentation:
The
water then goes to a sedimentation tank where the particles sink to the bottom
of the tank from which they are removed. Because of the action of the lime and
alum, the particles sink faster.
3.
Filtration:
Next
the water is passed through filter beds of sand and gravel. These remove the
smaller particles of dirt.
4.
Chlorination:
Although
the water now looks clear, it still contains harmful germs that are too small
to be filtered out small doses of chlorine gas are added to the water to kill
germs.
5.
Storage:
Now
that the water is clean and germ free, it is pumped along large underground
pipes called water mains, to storage tanks.
Long Q2: What is
distillation? Explain the process of distillation?
Ans: Distillation:
Distillation is the process of separating components of a
mixture based on different boiling points.
Experiment:
In this experiment we will separate ethanol from water.
Practical:
Let us take a mixture
of ethanol and water and kept in distilling flask which is heated by a burner.
The boiling point of ethanol is 78.4C , which is less then boiling point of
water which is 100C .
Ethanol at 78.4C
evaporates and passes through the glass tubes which are covered with condensing
apparatus. Now evaporated ethanol is condensed and it changes back to liquid
form and collected in receiving flask.
In this way we can
separate ethanol from water. In similar way we can separate impurities of sea
water by distilling sea water.
