-form-1-science-chapter-5-part-1

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)