01.
|
i |
ii |
iii |
iv |
v |
|
A |
A |
D |
B |
D |
02. Water is not lost around the globe because it
continuously recycled in the system called water
cycle.
03. Methods of domestic water purification are:
i.
Boiling
ii.
Use of
purifiers
iii.
Use of
commercial filters
04. (i) Water treatment is the process of
making water usable for domestic, industrial, medical and other purposes.
(ii) Water purification
is the removal of contaminants from treated water to produce drinking water
that is pure enough for human consumption.
05. Economic
activities of water
Ø
In
industries water is used in Manufacturing of goods like chemicals, food and
beverages, textiles and paper.
Ø
In
agriculture water is used:
o
For
irrigation
o
In
animal dips and for washing animals
Ø
In energy
production; water bodies are used to generate hydro-electrical energy.
Ø
In construction
water is used in construction of buildings and roads.
Ø
In
fishing activities; water bodies are used for fishing.
06. Physical and chemical properties of water
Physical properties of water
·
Pure
water is colourless, odourless and tasteless
·
It is
the substance which occur naturally in all states of matter i.e solid, liquid
and gas
·
Pure
water freezes at 00C and
boils at 1000C
·
Water
dissolves more substances than any other liquid and is usually called the
universal solvent.
·
It has
a high surface tension
·
It has
a high specific heat index
·
It
expands when it freezes
·
It is
miscible with many liquids example Ethanol
Chemical properties of
water
·
Pure
water is neutral.
·
Cold
water reacts with some metals to form metal hydroxides and liberate hydrogen
gas.
·
Some
metals react with steam to give respective metal oxide and hydrogen gas.
07. Main parts of the water cycle are:
Ø
Evaporation
(including transpiration)
Ø
Condensation
Ø
Precipitation
Ø
Collection
