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1. PRESENTED TO YOU BY:
Sumitrra Balasubramaniam
Zoe Khoo Mae Kim
Anabel Tan Shyin Lynn
Manuushya Nair a/p Veelayudan
Yaashvinhy Naidu a/p Kaleyarasli
Dini Fatihah bt. Baharom

2. NATURAL SOURCES OF
WATER
 Water from natural sources contains impurities. These impurities
are dissolved gases, microorganisms, decaying and dissolved
substances, suspended particles and wastes.
 Some dissolved substances in the water are poisonous and bad
for our health.
 Therefore, water must be treated before it can be used for
drinking. Water can be treated in several ways.

3. Methods of water
purification
filtration
boiling
chlorination
distillation

4. 1. FILTRATION
• Filtration removes the suspended solid particles such as clay and
sand in the water.
• The filtration process can be carried out by using sand particles as
the filter.
• This method of purification does not remove microorganisms and
dissolved substances.
• Therefore, filtered water is unsafe for drinking.

5.  Purifying water by
filtration

6.  PROCEDURE
1) Some river water is poured into the sand and stone filter as shown in
the figure.
2) The filtrate is collected in a beaker.
3) A drop of the filtrate is examined under a microscope.
4) A little of the filtrate is heated in a watch glass (as shown in the figure)
until all the water has evaporated.
The watch glass is examined.

7.  OBSERVATION
1. The water appears to be clear.
2. However, the water still contains living microorganisms. A powdery
residue is left on the watch glass.

8.  DISCUSSION
1. As the water flows through the sand filter, the suspended solid
particles are trapped between the layers of sand and stones.
2. Filtration does not remove dissolved substances and
microorganisms.
3. Therefore, filtered water is not suitable for drinking.

9.  CONCLUSION
 Filtered water still contains living microorganisms
and dissolved substances and is not safe for
drinking.

10. 2. boiling
 Water from natural sources may contain microorganisms. These
microorganisms can cause diseases such as cholera, diarrhoea and
typhoid.
 Boiling can kill most of the microorganisms in the water.
 This method can only supply a small amount of water safe for
drinking at home.
 However, boiling does not remove suspended particles and
dissolved substances in the water.

11.  Purifying water by
boiling

12.  PROCEDURE
1. A drop of filtered river water is placed on a glass side and observed
under a microscope.
2. Some filtrate is poured into a boiling tube.
3. The water in the boiling tube is then boiled.
4. A drop of the boiled water is examined under the microscope.

13.  OBSERVATION
1. River water that is not boiled contains microorganisms. These
microorganisms move actively in the water.
2. Microorganisms in boiled water are dead and no longer move.

14.  CONCLUSION
 Boiling kills the microorganisms in water.

15. 3. CHLORINATION
 Adding chlorine to water also kills microorganisms in it.
 This method is used to treat large quantities of water.
 The chlorination process is usually used in water purification plants
and swimming pools.
 However, too much chlorine in water gives the water an unpleasant
smell and is bad for health.

16.  PURIFYING WATER BY
CHLORINATION

17.  PROCEDURE
1. A little filtered river water is poured into a boiling tube.
2. A drop of water is placed on a glass slide and observed under a
microscope.
3. A few drops of chlorine are added to the water in the boiling tube.
4. A drop of the chlorinated water is then examined under a
microscope.

18.  OBSERVATION
 River water that has been filtered contains microorganisms. These
move actively in the water.
 The microorganisms in the chlorinated water are dead and do not
move anymore.

19.  CONCLUSION
 Chlorine kills the microorganisms in water.

20. 4. DISTILLATION
 Distillation of water produces pure water. This water is free from
microorganisms, dissolved substances and suspended particles.
 Pure water that is produced through distillation is called distilled
water.
 Distilled water is used to prepare chemical solutions in laboratories
and liquid medicines in pharmacies. It is also used widely in food
industries and as battery water in car batteries.

21.  PURIFYING WATER BY
DISTILLATION

22.  PROCEDURE
1. The apparatus is set up as shown in the figure.
2. The tap is turned on so that the water flows slowly into the Liebig
condenser.
3. Some river water in the distillation flask is boiled. The distilled water
(called distillate) is collected in a beaker.
4. A drop of the distilled water is examined under a microscope.
5. A few drops of distilled water are placed on a microscope slide and
evaporated until dry.
6. All observations are recorded.

23.  OBSERVATION
Steps Observation
Boiling the river water Vapour condenses in the Liebig
condenser and becomes water
that flows into the beaker
Examining the distilled water under Microorganisms are not present in
a microscope the distilled water
Examining the dried microscope No residue is left on the
slide microscope slide

24.  CONCLUSION
 Distillation removes all impurities from the water.