Quiz:
1. List down air composition and its percentage.
2. What is meant by air pollution?
3. Give 4 examples of air pollutant.
4. State 3 effects of air pollution on human health.
5. State 3 effects of air pollution on environment.
6. State 2 main sources of water pollution.
7. State 3 effects of water pollution on living things.
8. State 3 ways in controlling water pollution.
5.0 THE AIR AROUND US
5.1 The composition of Air.
1. Our Earth is surrounded by a layer of air called the atmosphere.— its protect living things on the Earth from harmful rays from the sun.
2. Air is a mixture of matters in the gaseous form --- air has mass and occupies space
3. Air is a mixture of different gases: nitrogen, oxygen, carbon dioxide and inert/rare gases (helium, neon, argon, krypton, xenon and radon).
4. Air also contains other component such as water vapour, dust and microorganisms.
5. Air is a mixture. This is because :
a) the components of air can be easily separated
b) Each component in air maintains its original properties.
c) The ratio of the components in the air changes according to the place and its surrounding.
d) by mixing nitrogen, oxygen, carbon dioxide, inert gases and water vapour together, air can be obtained.
6. Experiments to show some components in Air.
a. Experiment 1 : to determine the percentage of oxygen in the air.
b. Experiment 2 : to show that air contains water vapour, micro-organisms and dust particles.
Experiment 1 : The composition of Air
Aim: to determine the percentage of oxygen in the air.
Material/ apparatus: candle, water, basin, gas jar, gas jar stand and ruler.
Procedure:
1. The apparatus is set up as shown in figure 5.1
2. A gas jar is inverted over the candle and the water level in the gas jar is marked.
3. The height of the air column in the gas jar, P cm, is measured.
4. The gas jar is removed and the candle is lighted.
5. The gas jar is again inverted over the candle. The flame of the candle and the water level is observed.
6. When the flame goes, the water level in the gas jar is marked and the height of the air column in the gas jar, Q cm, is measured.
Result:
Height of air column at the beginning of activity, P, = 20 cm
Height of air column at the end of activity, Q = 16 cm
Percentage of oxygen in the air = 20 - 16 x 100% = 20 %
20
Discussion:
1. The candle continues to burn but gets progressively dimmer and finally extinguishes.
2. The candle burns by using the oxygen in the gas jar.
3. The flame of the candle extinguishes when there is no more oxygen in the gas jar.
4. The water level is rises to replace the oxygen content that has been used up when the candle burns.
5. The water level in the gas jar increases and occupies about 1/5 of the jar.
6. This shows that 1/5 of the air in the gas jar is oxygen.
7. Thus, oxygen makes up about 20% of the air.
Conclusion:
The percentage of oxygen in the air is approximately 20 %.
Experiment 2 :
Aim : to show that air contains water vapour, micro-organisms and dust particles.
A. Air contains water vapour.
Material/apparatus : Ice, water, rubber stopper, U –tube and dry cobalt chloride paper.
Procedure :
1. The apparatus is set up as shown in figure 5.2. Some ice cubes are placed into the U-tube.
2. the U-tube is dried and covered with a stopper.
3. The U –tube is left aside for a few minutes. The droplets observed are tested with dry cobalt chloride paper.
Observation ;
1. After 10 minutes, clear and colourless liquid droplets are seen forming on the outer wall o one end of the U- tube which has ice inside it.
2. When tested, the dry blue cobalt chloride paper turns pink.
Discussion :
1. The dry blue chloride paper is used to test for the presence of water.
2. The presence o water will turn the dry blue cobalt chloride paper pink.
3. This activity proves that the liquid formed on the external surface of the U-tube is water.
4. Air contains water vapour. It condenses to become liquid on the outer wall of one end of the U-tube that has ice inside it.
Conlusion :
Air contains water vapour.
B. Air contains micro-organisms.
Materials/ apparatus : Two petri dishes containing sterilised nutrient agar , cellophane tape.
Procedure :
1. set up two Petri dishes as shown in the diagram.
2. Expose the agar in dish P to the air for about 10 minutes before the dish is sealed.
3. Do not expose the agar in dish Q to the air. Seal the dish as soon as it is prepared.
4. Invert the two Petri dishes and keep them aside for 48 hours.
Observation :
Petri dish Observation
P Many white spots of microorganisms on the surface of the agar.
Q Does not contain any white spots on the agar.
Discussion :
1. The nutrient agar in Petri dish P contains white spot o microorganisms even though it is sterilized. This is because it is exposed to the microorganisms in the air.
2. The nutrient agar in Petri dish Q does not contain white spot of microorganisms . It is sterilized and tightly closed. Therefore, it is not affected by microorganisms.
3. This shows that air contains microorganisms.
Conclusion :
Air contains microorganisms.
C. Air contains dust.
Materials/apparatus : Three glass slides, cellophane tape, Petri dish and magnifying glass.
Procedure:
1. Three strips of cellophane tape of the same length are cut.
2. Each cellophane tape is pasted separately on three slides labeled X, Y and Z, with the sticky surface facing up.
3. the slide labeled X is placed in a covered petri dish (control set).
4. The slides labeled Y and Z are placed in the laboratory and in the canteen respectively.
5. After three days, the surface of the cellophane tape is observed with magnifying glass.
Observation:
The slide kept in the Petri dish is clean; the slide kept in the laboratory is covered with thin layer of dust while the slide kept in canteen is covered with thick layer of dust.
Discussion :
1. The surface of the cellophane tape in the Petri dish is clean because it is kept in enclosed area.
2. The air in the canteen contains more dust than the air in the laboratory.
Conclusion:
Air contains dust.
5.1 The composition of Air.
1. Our Earth is surrounded by a layer of air called the atmosphere.— its protect living things on the Earth from harmful rays from the sun.
2. Air is a mixture of matters in the gaseous form --- air has mass and occupies space
3. Air is a mixture of different gases: nitrogen, oxygen, carbon dioxide and inert/rare gases (helium, neon, argon, krypton, xenon and radon).
4. Air also contains other component such as water vapour, dust and microorganisms.
5. Air is a mixture. This is because :
a) the components of air can be easily separated
b) Each component in air maintains its original properties.
c) The ratio of the components in the air changes according to the place and its surrounding.
d) by mixing nitrogen, oxygen, carbon dioxide, inert gases and water vapour together, air can be obtained.
6. Experiments to show some components in Air.
a. Experiment 1 : to determine the percentage of oxygen in the air.
b. Experiment 2 : to show that air contains water vapour, micro-organisms and dust particles.
Experiment 1 : The composition of Air
Aim: to determine the percentage of oxygen in the air.
Material/ apparatus: candle, water, basin, gas jar, gas jar stand and ruler.
Procedure:
1. The apparatus is set up as shown in figure 5.1
2. A gas jar is inverted over the candle and the water level in the gas jar is marked.
3. The height of the air column in the gas jar, P cm, is measured.
4. The gas jar is removed and the candle is lighted.
5. The gas jar is again inverted over the candle. The flame of the candle and the water level is observed.
6. When the flame goes, the water level in the gas jar is marked and the height of the air column in the gas jar, Q cm, is measured.
Result:
Height of air column at the beginning of activity, P, = 20 cm
Height of air column at the end of activity, Q = 16 cm
Percentage of oxygen in the air = 20 - 16 x 100% = 20 %
20
Discussion:
1. The candle continues to burn but gets progressively dimmer and finally extinguishes.
2. The candle burns by using the oxygen in the gas jar.
3. The flame of the candle extinguishes when there is no more oxygen in the gas jar.
4. The water level is rises to replace the oxygen content that has been used up when the candle burns.
5. The water level in the gas jar increases and occupies about 1/5 of the jar.
6. This shows that 1/5 of the air in the gas jar is oxygen.
7. Thus, oxygen makes up about 20% of the air.
Conclusion:
The percentage of oxygen in the air is approximately 20 %.
Experiment 2 :
Aim : to show that air contains water vapour, micro-organisms and dust particles.
A. Air contains water vapour.
Material/apparatus : Ice, water, rubber stopper, U –tube and dry cobalt chloride paper.
Procedure :
1. The apparatus is set up as shown in figure 5.2. Some ice cubes are placed into the U-tube.
2. the U-tube is dried and covered with a stopper.
3. The U –tube is left aside for a few minutes. The droplets observed are tested with dry cobalt chloride paper.
Observation ;
1. After 10 minutes, clear and colourless liquid droplets are seen forming on the outer wall o one end of the U- tube which has ice inside it.
2. When tested, the dry blue cobalt chloride paper turns pink.
Discussion :
1. The dry blue chloride paper is used to test for the presence of water.
2. The presence o water will turn the dry blue cobalt chloride paper pink.
3. This activity proves that the liquid formed on the external surface of the U-tube is water.
4. Air contains water vapour. It condenses to become liquid on the outer wall of one end of the U-tube that has ice inside it.
Conlusion :
Air contains water vapour.
B. Air contains micro-organisms.
Materials/ apparatus : Two petri dishes containing sterilised nutrient agar , cellophane tape.
Procedure :
1. set up two Petri dishes as shown in the diagram.
2. Expose the agar in dish P to the air for about 10 minutes before the dish is sealed.
3. Do not expose the agar in dish Q to the air. Seal the dish as soon as it is prepared.
4. Invert the two Petri dishes and keep them aside for 48 hours.
Observation :
Petri dish Observation
P Many white spots of microorganisms on the surface of the agar.
Q Does not contain any white spots on the agar.
Discussion :
1. The nutrient agar in Petri dish P contains white spot o microorganisms even though it is sterilized. This is because it is exposed to the microorganisms in the air.
2. The nutrient agar in Petri dish Q does not contain white spot of microorganisms . It is sterilized and tightly closed. Therefore, it is not affected by microorganisms.
3. This shows that air contains microorganisms.
Conclusion :
Air contains microorganisms.
C. Air contains dust.
Materials/apparatus : Three glass slides, cellophane tape, Petri dish and magnifying glass.
Procedure:
1. Three strips of cellophane tape of the same length are cut.
2. Each cellophane tape is pasted separately on three slides labeled X, Y and Z, with the sticky surface facing up.
3. the slide labeled X is placed in a covered petri dish (control set).
4. The slides labeled Y and Z are placed in the laboratory and in the canteen respectively.
5. After three days, the surface of the cellophane tape is observed with magnifying glass.
Observation:
The slide kept in the Petri dish is clean; the slide kept in the laboratory is covered with thin layer of dust while the slide kept in canteen is covered with thick layer of dust.
Discussion :
1. The surface of the cellophane tape in the Petri dish is clean because it is kept in enclosed area.
2. The air in the canteen contains more dust than the air in the laboratory.
Conclusion:
Air contains dust.
salam perkenalan
Salam sejahtera...... terima kasih kerana singgah di laman ini..... moga pertemuan di laman ini akan dimanafaatkan untuk kita sama-sama berkongsi ilmu kurniaanNya...ilmu yang baik seharusnya kita sebarkan untuk diamalkan demi kebaikan semua....ini saja untuk kali ini......
Subscribe to:
Posts (Atom)
