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Science form 1(Chapter5-part2)
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SCIENCE Form 1
UNIT 5 :
The Air Around Us
1yschow@smkbpj(a)
5.1 The Composition of Air
• The Earth’s surface is surrounded by a larger of air known as atmosphere
• Air is a mixture of various substances which is tasteless, colourless and odourless but we can feel it through wind when it moves
2yschow@smkbpj(a)
• Nitrogen, oxygen, carbon dioxide and inert
gases have a fixed percentage of component
in the mixture of air
3yschow@smkbpj(a)
• Other substances such as dust,
microorganisms and water vapour can also be
found in the air but their contents vary
depends on the quality of air of that
environment
4yschow@smkbpj(a)
Inert gas / noble gas
Helium Xenon For sun lamps
Krypton
for fluorescent bulbs.
Helium Xenon For sun lamps
For earthquake prediction Neon for light
5yschow@smkbpj(a)
To determine the percentage of oxygen in air
• As the candle continue to burn the flame get smaller and finally it goes off. smaller and finally it goes off.
• The water lever increases and occupied the space of oxygen in the gas jar.
Conclusion:
Oxygen makes up of approximately 21% of the volume of air.
6yschow@smkbpj(a)
Air contains water vapour
• Water droplets that formed on the outer wall of the test • Water droplets that formed on the outer wall of the test tube can be clearly seen.
• Collect the liquid droplets and test with a blue cobalt chloride paper. The paper then turns to pink in colour, this proofs that the liquid is water.
Conclusion
• Air contains water vapour. 7yschow@smkbpj(a)
Air contains microorganisms
Coloured spots of microorganisms (fungi) are
found on the surface of the nutrient agar
Conclusion:
Air contains microorganisms.8yschow@smkbpj(a)
Air contains dust
Dust can be seen on the sticky surface of glass Dust can be seen on the sticky surface of glass
slide.
Conclusion :
Air contains dust.
9yschow@smkbpj(a)
Exercise 5.1
10yschow@smkbpj(a)
21 %
78 %
0.03 %
0.97 %
11yschow@smkbpj(a)
5.2 The Properties of Oxygen and Carbon Dioxide
• Oxygen and carbon dioxide are the two main
gases that made up the air for sustaining life
• The properties of gases can be studied and • The properties of gases can be studied and
observed by carrying out the following tests
12yschow@smkbpj(a)
Test 1: Solubility in water
Oxygen Carbon dioxideOxygen
• The water level in the test
tube rises slightly
• Oxygen only dissolve a little
in water
• The water level in the test
tube rises a lot.
• Carbon dioxide is soluble in
water
13yschow@smkbpj(a)
Test 2: Reaction with sodium hydroxide
Oxygen Carbon dioxideOxygen
• The level of sodium
hydroxide solution in the
test tube does not change
• Oxygen is not soluble in
sodium hydroxide
• The level of sodium
hydroxide solution in the
test tube rises a lot
• Carbon dioxide is very
soluble in sodium hydroxide
14yschow@smkbpj(a)
Test 3: Glowing wooden splinter
Oxygen Carbon dioxideOxygen
• The glowing wooden
splinter bursts into flame
• Oxygen helps in combustion
• The glowing wooden
splinter extinguished
• Carbon dioxide does not
help in combustion
15yschow@smkbpj(a)
Test 4 : Burning wooden splinter
Oxygen Carbon dioxideOxygen
• The burning wooden
splinter burns brightly
• Oxygen supports
combustion
• The burning wooden
splinter extinguished
• Carbon dioxide does not
supports combustion
16yschow@smkbpj(a)
Test 5: Tested with moist litmus paper
Oxygen Carbon dioxideOxygen
• The colour of both litmus
paper does not change
• Oxygen is neutral
• The colour of blue litmus
paper turns red
• Carbon dioxide is acidic
17yschow@smkbpj(a)
Test 6: Lime water test
Oxygen
• No change
Carbon dioxide
• The lime water turns chalkychalky
18yschow@smkbpj(a)
Test 6: Bicarbonate indicator test
Oxygen Carbon dioxideOxygen
• The red colour of indicator
does not change
• Oxygen in neutral
• The red colour of indicator
turns yellow yellow
• Carbon dioxide is acidic
19yschow@smkbpj(a)
20yschow@smkbpj(a)
21yschow@smkbpj(a)