§15.5 Water supply
Uses of water
1. Water in industry
• As a coolant to reduce the
of some industrial processes (Cold-water
pipes are coiled around the tanks.), e.g.: in
stations, it is heated
to make steam. The steam then drives the
that generate electricity.
• Watering
, and is needed as a drink for
.
• As a
in many chemical production processes.
• Hydroelectric power stations to generate electricity.
• As a first raw material for many processes, e.g.: the production of
from
ethene and steam.
2. Water in homes
• Drinking, cooking and washing.
• General
.
• In car radiators, for gardens and plants.
Sources of water
• Much of the water we use is taken from
.
• Some is pumped up from below ground. This underground water is called
A large area of rock may hold a lot of groundwater, like a sponge. This rock is called
an
.
.
Implications of an Inadequate Supply of Water
• Clean and safe water supply is very important to mankind
• Many problems arise in the event of an inadequate water supply, including:
1)
and
without a clean water supply;
2) Poor sanitation leads to the spread of
water becomes infected.
due to a lack of crops which cannot grow
and
as drinking
Water treatment
• Untreated water contains
•
•
•
•
•
•
and
impurities;
Insoluble impurities include soil, pieces of plants and other organic matter;
Soluble impurities include dissolved calcium, metallic compounds and inorganic
pollutants;
is the process used to remove large insoluble particles by passing the
water through layers of sand and gravel filters that trap larger particles;
But
and other
are too small to be trapped by the filters
so
is used;
This involves the careful addition of chlorine to the water supply which kills
and other
;
and
are examples of bacterial diseases which can arise
by the consumption of untreated water.
Credit to Hannah, Josie, Jonas, Jonathan from G2-A
Providing a water supply on tap
1
2
3
4
Find a clean
– a river or aquifer – to pump water from.
Remove as many
particles from the water as you can, like making fine
particles stick together and skim them off, or filtering the water through clean gravel
or sand.
Add something to kill the microbes in the water. (Usually
.)
Store the water in a clean covered
, ready for pumping to taps.
A modern treatment plant
1
2
3
4
5
6
7
8
The water is pumped in. A
traps any big particles, such as wigs.
A
is added – a chemical to make small suspended particles stick
together. It could be iron(III) sulfate, for example.
Next,
is blown through the water in flotation tanks, to make the coagulated
particles float to the
. They are skimmed off.
The water is passed through a bed of fine sand to
it.
It may go through further filters. For example more sand, or charcoal to remove bad
tastes and smells.
is added to kill bacteria and other microbes.
A
compound is added in some plants, to help fight
.
The water is pumped to the
, ready for pumping to homes.
Chemical tests for water
• Cobalt(II) chloride turns
to
on the addition of water. This test is
usually done using cobalt chloride paper.
→The equation is: CoCl2(s) + 6H2O(l) ⇌ CoCl2·6H2O(s)
• Anhydrous copper(II) sulfate turns
to
on the addition of water.
→The equation is: CuSO4(s) + 5H2O(l) ⇌ CuSO4·5H2O(s)
Note: If a liquid is
, it will also boil at 100℃, and freeze at 0℃.
Credit to Hannah, Josie, Jonas, Jonathan from G2-A