Science form 1(Chapter5-part2)

1. SCIENCE Form 1
UNIT 5 :
The Air Around Us
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2. 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
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3. • Nitrogen, oxygen, carbon dioxide and inert
gases have a fixed percentage of component
in the mixture of air
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4. • 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
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5. Inert gas / noble gas
Krypton
for fluorescent bulbs.
Helium Xenon For sun lamps
yschow@smkbpj(a) Neon for light 5
For earthquake prediction

6. To determine the percentage of oxygen in air
• As the candle continue to burn the flame get
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.
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7. Air contains water vapour
• 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.
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8. Air contains microorganisms
Coloured spots of microorganisms (fungi) are
found on the surface of the nutrient agar
Conclusion:
Air contains microorganisms.
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9. Air contains dust
Dust can be seen on the sticky surface of glass
slide.
Conclusion :
Air contains dust.
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10. Exercise 5.1
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11. 21 %
78 %
0.03 %
0.97 %
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12. 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
observed by carrying out the following tests
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13. Test 1: Solubility in water
Oxygen Carbon dioxide
• The water level in the test • The water level in the test
tube rises slightly tube rises a lot.
• Oxygen only dissolve a little • Carbon dioxide is soluble in
in water water
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14. Test 2: Reaction with sodium hydroxide
Oxygen Carbon dioxide
• The level of sodium • The level of sodium
hydroxide solution in the hydroxide solution in the
test tube does not change test tube rises a lot
• Oxygen is not soluble in • Carbon dioxide is very
sodium hydroxide soluble in sodium hydroxide
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15. Test 3: Glowing wooden splinter
Oxygen Carbon dioxide
• The glowing wooden • The glowing wooden
splinter bursts into flame splinter extinguished
• Oxygen helps in combustion • Carbon dioxide does not
help in combustion
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16. Test 4 : Burning wooden splinter
Oxygen Carbon dioxide
• The burning wooden • The burning wooden
splinter burns brightly splinter extinguished
• Oxygen supports • Carbon dioxide does not
combustion supports combustion
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17. Test 5: Tested with moist litmus paper
Oxygen Carbon dioxide
• The colour of both litmus • The colour of blue litmus
paper does not change paper turns red
• Oxygen is neutral • Carbon dioxide is acidic
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18. Test 6: Lime water test
Oxygen Carbon dioxide
• No change • The lime water turns chalky
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19. Test 6: Bicarbonate indicator test
Oxygen Carbon dioxide
• The red colour of indicator • The red colour of indicator
does not change turns yellow
• Oxygen in neutral • Carbon dioxide is acidic
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