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Chapter 5 - IAS
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Properties of mineral, Reaction of metals with oxygen and sulphur, reactions of calcium carbonate
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UNIT 5 : The Air Around Us yschow@smkbpj(a)
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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 tasteless,, colourless and odourless but we can feel it through wind when it moves yschow@smkbpj(a)
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• Nitrogen, oxygen, carbon dioxide and inert gases have a fixed percentage of component in the mixture of air
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• 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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Inert gas / noble gas
Krypton for fluorescent bulbs.
yschow@smkbpj(a)
For earthquake prediction
Neon for light
5
To determine the percentage of oxygen in air
• As the candle continue to burn the flame get . • The water water lever increases and occupied occ upied the space of oxygen in the gas jar. Conclusion: Oxygen makes up of approximately 21% of the volume volume of of air air.. yschow@smkbpj(a)
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Air contains water vapour
tube can be clearly seen.
• Collect the liquid l iquid droplets and test with a blue cobalt chloride paper. The paper then turns to pink in colour colour,, this thi s proofs that the liquid is water. water. Conclusion • Air contains water vapour. yschow@smkbpj(a)
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Air contains microorganisms
Coloured spots of microorganisms (fungi) are found on the surface of the nutrient agar Conclusion: Air contains microorganisms. yschow@smkbpj(a)
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Air contains dust
slide. Conclusion : Air contains dust. yschow@smkbpj(a)
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Exercise 5.1
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21 % 78 % 0.03 % 0.97 %
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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
• T e properties o gases can e stu ie an observed by carrying out the following tests
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Test 1: Solubility in water
Ox
Carbon dioxide
en
• The water level in the test tube rises slightly
tube rises a lot. lot.
• Oxygen only dissolve a little in water
• The water level in the test
• Carbon dioxide is soluble in water
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Test 2: Reaction with sodium hydroxide
Ox
Carbon dioxide
en
• The level of sodium
• The level of sodium
hydroxide solution in the test tube does not change
• Oxygen is not soluble in sodium hydroxide
hydroxide solution in the test tube rises a lot
• Carbon dioxide is very soluble in sodium hydroxide yschow@smkbpj(a)
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Test 3: Glowing wooden splinter
Ox
Carbon dioxide
en
• The glowing wooden
• The glowing wooden
splinter bursts into flame
splinter extinguished
• Oxygen helps in combustion
dioxide does not • Carbon dioxide help in combustion
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Test 4 : Burning wooden splinter
Ox
en
• The burning wooden splinter splinter burns brightly
• Oxygen supports combustion
Carbon dioxide
• The burning wooden splinter extinguished dioxide does not • Carbon dioxide supports combustion
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Test 5: Tested with moist litmus paper
Ox
Carbon dioxide
en
The colour colour of both both litmu litmuss • The paper does not change
• Oxygen is neutral
• The colour of blue litmus paper turns red
• Carbon dioxide is acidic
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Test 6: Lime water test
Oxygen
• No change
Carbon dioxide
• The lime water turns chalky
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Test 6: Bicarbonate indicator test
Ox
Carbon dioxide
en
• The red colour of indicator does not change
• Oxygen in neutral
colourr of indic indicat ator or • The red colou turns yellow
