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
NATURAL SOURCES OFWATER 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.
Methods of waterpurification filtration boiling chlorination distillation
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.
Purifying water by filtration
PROCEDURE1) 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.
OBSERVATION1. The water appears to be clear.2. However, the water still contains living microorganisms. A powdery residue is left on the watch glass.
DISCUSSION1. 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.
CONCLUSION Filtered water still contains living microorganisms and dissolved substances and is not safe for drinking.
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.
Purifying water by boiling
PROCEDURE1. 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.
OBSERVATION1. 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.
CONCLUSION Boiling kills the microorganisms in water.
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.
PURIFYING WATER BY CHLORINATION
PROCEDURE1. 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.
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.
CONCLUSION Chlorine kills the microorganisms in water.
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.
PURIFYING WATER BY DISTILLATION
PROCEDURE1. 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.
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
CONCLUSION Distillation removes all impurities from the water.