chapter 5-the air around us

7/29/2019 Chapter 5-The Air Around Us

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The Air Around Us


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Air


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Air

Air

Compositionof air

Air pollution

OxygenCarbon dioxide

Respiration Combustion

Examples Sources Effect

Importance ofclean air


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The Air Around Us

1. Air is a mixture of

a. Nitrogen78%

b. Oxygen - 21%

c. Carbon dioxide0.03%

d. Inert gases - 0.97%

e. Water vapourvaries

f. Micro-organisms

g. Dust

Nitrogen(78%)

Oxygen(21%)

Inert gases + othersubstances (0.97%)

Carbon dioxide(0.03%)

2. The composition of air such as water vapour, micro-organisms and dust are varies with time and places. Forexamples, after rain, there will be more water vapourcompared to a hot dry day.

3. Air is a mixture since its components can be easily

separated. For example, water vapour in the air can beseparated by condensation.


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Air

GasesOther

component

Fill in each blank to show the composition of air

Exercise


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a) The component of air can be easily separated

b) Each component found in the air still

maintains its original its properties

c) By mixing nitrogen, oxygen, carbon dioxide,inert gases and water vapour together, air can

be obtained

d) The ratio of the components in the air changes

according to the place and its surroundings

Why air is mixture?


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Why air is mixture?

Air is a mixture. This is because :a) The proportion of the constituent gases,

namely, nitrogen, oxygen and carbondioxide is not constant

The contents by percentage of air vary fromto place to place. For example, the air inurban areas contains more dust and carbondioxide

the components are mixed and vary inquantity not chemically combined


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b) the constituents of air are not chemicallycombined

the constituents gases retain their individual

propertiesnitrogen, oxygen and carbon dioxide can be

extracted by the physical means of coolingand stored as liquefied gas in gas tanks

c) the properties of air are the same as theproperties of its constituents

oxygen in air can be used in processes suchas respiration, burning, decaying and rusting

carbon dioxide in air is used for the process

of photosynthesis in green plantsd) there is no heat change when there is a

change in the percentage of theconstituents of air in any particular area


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Situation Description

Time

Condition

Environment

Activities

The composition of air is not fixed. Explain how itchance according to


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Composition of air1. Oxygen

Arrangement of apparatus

After 15 minutes

Flame goes off

Water levelgoes up 1/5 ofthe gas jar.

a. When candle burns, it uses up all the oxygen in thegas jar.

b. Water goes into the gas jar to fill up the space whichwas originally occupied by oxygen.

c. This conclude that 1/5 of the air is made up of oxygen.

0

1

2

3

4

0

1

2

3

4

1

2

0


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Composition of Air

2. Water Vapour

Colourless liquid iswater as it changesblue anhydrouscobalt chloridepaper pink

Boiling tube

IceWater

After 15

minutes


a. The experiment shows that air contains water vapour.

b. Water vapour condenses and becomes water outside the boiling tube.

Water vapour ( gas )condensation

Water ( liquid )


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Composition of air

3. Microorganisms

Agar in

goodcondition

After 3

daysYellowish-white

particles(colonies of

bacteria)


At the beginning At the end

This experiment shows there are microorganisms in the air.


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Composition of air

4. Dust particles

Dust on cellophane stripafter it is left expose

Glassslide


This experiment shows that air contain dust particles


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Properties of Oxygen and Carbon Dioxide

Solubility in water

Oxygen Activity Carbon dioxide

Test tube

Beaker

Water

Gas

Water level in thetest tube goes up a

little.

Slightly soluble in

water.

Water level in thetest tube goes up

slightly higher.

More soluble in

water than oxygen.

Test tube

Beaker

Sodium

hydroxidesolution

Gas

Reaction with sodiumhydroxide

Nothing happen.

Not soluble in

sodium hydroxide.

Level of solution

in the test tube is

high.

Very soluble in

sodium hydroxide.

Effect on glowingwooden splinter.

glowingwoodensplinter.

Gas

Light up the glowing

splint.

Support combustion.

Test for oxygen.

Put out the

glowing splint.

Does not support

combustion.


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Effect on burningwooden splinter.


The lighted splint

burn more brightly.

Support

combustion

Put out burning

splinter.

Does not support

combustion.

Effect on moist litmus.Nothing happens.

Not soluble in

sodium hydroxide.

Blue litmus paper

turns red.

An acidic gas.

Burning

woodensplinter.

Gas

Gas

Moist litmuspaper


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Effect on lime water.


Nothing happens.

No effect on lime

water.

Lime water turns

chalky

Test for carbon

dioxide.

Effect on bicarbonateindicator.

Nothing happens.

No effect on

bicarbonateindicator.

Bicarbonate

indicator changes

colour from red to

yellow.

An acidic gas

Gas

Lime water

Gas

Bicarbonateindicator


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1. Oxygen and carbon dioxide are both colourless andodourless gas.

2. Oxygen is neutral and support combustion.

3. The presence of oxygen can be tested with a glowingwooden splinter. The glowing wooden splinter rekindles in

the presence of oxygen.4. Carbon dioxide is an acidic and does not support

combustion.

5. The presence of carbon dioxide can be tested with limewater. Lime water will turn chalky or cloudy in the

presence of carbon dioxide.


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Respiration BreathingChemical process

involving the oxidation of

food by oxygen in cell torelease energy

Physical process of

taking in oxygen from the

air and releasing carbondioxide

Comparison between respiration and breathing

Oxygen +glucose

respiration energy +carbon dioxide+ water vapour


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Oxygen is Needed in Respiration

1. Products of respiration areenergy, carbon dioxide andwater vapour.

2. During respiration, living thingsuse oxygen and give outcarbon dioxide.

3. An equation in words to showrespiration.

Oxygen + glucose

respiration

energy + carbon dioxide + water vapour

Living cell

Energy

Glucose

WaterNucleusCarbon

dioxide

Oxygen


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Comparison between contents ofinhaled and exhaled air.

Gas Inhaled air (%) Exhaled air (%)

Oxygen 21 16

Carbon dioxide 0.03 4

Nitrogen 78 78

Water vapour Less More


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The contents of Oxygen in inhaled andexhaled of humans.

P Q

Inhaled air exhaled air


CandleCandle Plasticine

Gasjar

1. Candle flame burns longer in the gas jar P than gas jar Q.

2. This show inhaled air contains more oxygen than exhaled air.


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Exhaled air contain more carbon dioxide


Lime water

Conical

flask QConicalflask P

Breath in and out

Tube X

1. When air is breathed in and out alternatively through the tube X for afew minutes, lime water in conical flask Q becomes cloudy faster thanthe lime water in conical flask P.

2. This shows that exhaled air contains more carbon dioxide than

inhaled air.


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Label diagram below


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Compare the percentage of gas in inhaled

and exhaled air in the spaces provided below.


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Living things use oxygen duringrespiration

W

Germinating

seeds

Cotton wool

(soaked in sodiumhydroxide solution)

Marker

X

Grasshopper

Cotton wool

(soaked in sodium

hydroxide solution)

Marker

Steel

wool

Steelwool

Y

Cotton wool

(soaked in sodium

hydroxide solution)

Marker

Steel

wool


Control

experiment


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Living things use oxygen duringrespiration

1. After some time, the marker moves towards

a. The germinating seeds in test tube W.

b. The grasshopper in test tube X.2. The marker in test tube Y does not move at all.

3. This shows the germinating seeds and grasshopper use upoxygen in the test tube and give out carbon dioxide whichis absorbed by the sodium hydroxide solution.

4. This cause a decrease in the volume of air inside the testtube, causing the marker to move inwards.

5. Test tube Y is a control.

From the experiment:


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Oxygen is Needed for Combustion

Fuel

Heat Oxygen

The three conditions tocombustion.

1. Combustion:

a. Commonly known as burning .

b. A chemical reaction of substance

with oxygen.

c. Give out heat and light.

d. Take place when oxygen, fuel and

heat present.

2. Oxygen is required in the burning of carbon and hydrocarbon.

a. Carbon + oxygen carbon dioxide + heat + light.b. Hydrocarbon + oxygen carbon dioxide + water+ heat + light.

3. Examples of carbon are charcoal and coal.

4. Example of hydrocarbon are kerosene, petrol, diesel, petroleum gas

and candles.


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The three conditions to combustion.

The diagram shows the three conditions to combustion. Fill the space provided with the

required conditions.

What is combustion?


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Combustion of carbon in oxygen

Gas jar

Deflagratingspoon

Oxygen

Carbonburning

Bicarbonate

indicator


Observation Conclusion

The gas jar feel hot Heat energy is released.

Carbon burns brightly Light energy is released.

Bicarbonate indicator turns yellow Carbon dioxide is released.

The observation and conclusion of the experiment carried out

Combustion of carbon produces heat, light and carbon dioxide.


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What air pollution is?

When substances that are harmful to our health

or that can cause damage to our environment

are found in the air

any visible or invisible substances in theatmosphere that pose a threat to human or theenvironment, and can arise from human &natural sources

Eg:

1. Dust, 4. Carbon dioxide

2. Soot 5. pesticides

3. Smoke


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Examples ofair pollution

Source ofpollution

Effect on man andenvironment

Sulphur

dioxide and

oxide of

nitrogen

(nitrogendioxide)

Burning of fossil

fuels

Burning of

rubbish

Cause acid rain corrode

metal and stone structure

Reduce the yield of plant

Carbon

monoxide

Cigarette

smoke

Incomplete

combustion offuels

Cause brain damage

If severe, man may die

because it prevents the

red blood cells fromtransporting oxygen

around the body

Carbon

dioxide

Burning of fuels

Forest fire

Causes global warning

and green house effect.


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Dust (haze)

Constructionsite

Cement plant

Causesdifficulties in

breathing.Lung cancer

Smoke and soot

Burning ofrubbish and fuels

Cigarettesmoke

Cause haze

Cause breathing

difficulties.

Chlorofluorocarbon

(CFC)

Aerosol sprays

Refrigerator

and airconditioner

Damage theozone layer

Causes cataractin eyes

LeadBurning ofleaded fuels

Causes damageto brain, heart

and kidneys.


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Pollutants

Cause the air become hazy & cause :

1. Low visibility

2.

Breathing difficulties3. Reduction in the rate of photosynthesis


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Enforcement of anti-pollution law

Enforcement of the Clear Air Act 1979

1.

ensure that industrial activities are not carriedout in a housing area

2. open burning is not carried out

3. chimneys of factories are built to certain height


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Managing pollutant

Include:

1. Removing sulphur from fuels

2.

Using catalytic converters to make poisonousfumes from car engines harmless

3. Fixing electronic devices on chimneys to trap

dust, smoke & soot


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Air Pollution

a. Green house effect

i. Carbon dioxide is given out when fuelsare burned. It remain in the atmosphere.

ii. Carbon dioxide acts like blanket which

retain heat. This causes the Earth to warmup slowly, leading to the green houseeffect.

iii. The green house effect may cause

The polar ice caps to melt which will raisethe sea level

The climate to change.

3. Pollution from combustion causes


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b. Acid rain

i. Most fossil fuels contain sulphur impurities.

ii. These turn into sulphur dioxide when thesulphur is burned.

iii. Oxide of nitrogen are released when fossil

fuels are burned.iv. Sulphur dioxide and oxides of nitrogen

mix with cloud to form acid.

v. These then fall as acid rain.

vi. Cars and power stations are the maincauses of acid rain.


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Air Pollution

4. Effects of acid rain on the environment

a. Acid rain causes lakes to become acidicwhich has a severe effect on theirecosystem.

b. Acid rain kills fish and trees.

c. Acid rain damages limestone buildingsand ruins stone statues.

Ai P ll ti


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Air Pollution5. Thinning of the ozone layer

a. The ozone layer protects the Earth from excessive ultraviolet rays

from the sun.

b. 95% - 99% of ultraviolet rays can be blocked by the ozone layer,

preventing it from reaching the Earth.

c. Ultraviolet rays can cause skin cancer (melanoma), eyes cataract

and weakened the body immune system.

d. Chlorofluorocarbon (CFC) can cause the ozone layer to corrode.

Ultraviolet

rays

Sun

Ozone layer

The ozone

layer

protects the

earth from

the sunsultraviolet

rays.

The

thinning of

ozone

layer

causes theultraviolet

rays to

reach the

Earth.

Thinning of the ozone layer


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Steps to Control Air Pollution

Steps to controlair pollution

Equip carswith catalytic

converter

Filter smoke fromfactories before

releasing it

Set up factoriesfar away from

housing estate.

Ban open

burning ofrubbish

Encouragereforestation

Frequent anti-smoking

campaign

Use unleadedpetrol

Control the use ofchlorofluorocarbon


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The important of Keeping the Air Clean

1. When the air is clean:

a. The quality of air increases and health problems associatedwith air pollution will decrease.

b. The yield of crops will be better.

c. Global warming can be controlled.

d. The world become a better place to live.

2. We should practice good habits that keep the world clean.

a. Recycle papers, bottles and can to reduce waste.

b. Use unleaded petrol to reduce lead particles in the air.

c. Practice car pooling or use public transports to reduce thenumber of cars on the road.

d. Use less chlorofluorocarbon (CFC).

e. Save electricity so that less fossil fuels have to be burnt to

provide electricity.


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Aim : To show the pollutants in

cigarette smoke

P ll t t i Ci tt S k


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Pollutants in Cigarette Smoke

Thinning of the ozone layer

Thermometer

Cigarette

Cotton wool

Glass tube

Rubber tubingTo pump

ConicalflaskHydrogen

carbonateindicator

1. The thermometer gives a higher reading.

2. The white cotton wool turns brown after a few minutes.

3. The hydrogen carbonate indicator turns yellow.4. These show that cigarette smoke:

a. Is warm

b. Contain pollutants

c. Is acidic.

P ll i Ci S k


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1. Smoking cigarette pollutes the air because its smoke

contains more than 4000 chemicals

2. Nicotine, tar and carbon monoxide are some examplesof pollutants in cigarette smoke.

3. Nicotine is a drug that act upon the brain and thenervous system. Smokers become addicted to it.

4. Tar damage the cilia of the air passage and blocks thetiny air passage leading to the alveoli

5. Carbon monoxide is a deadly gas; tend to combine withthe haemoglobin in red blood cells, thus reducing theamount of oxygen that the blood can carry

Pollutants in Cigarette Smoke


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Life without clean air

Health problem lead can causes blood

poisoning & brain damage; smoke in the air can

cause lung infection

A reduction in agriculture production dust

sticks to leaves & slow down the process of

photosynthesis

Blurred vision dust or smoke in the air blursvision ACCIDENT


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Life without clean air

Animals will fall sick & will eventually die

The greenhouse effect man will live in a

warmer environment

Deformities radioactive wastes causes

deformities in unborn babies

Acid rain metal objects corrode and the

pH of soil & water sources is lowered

R d d l d i


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Reduce, reuse and recycle used itemswhenever possible. Buy and use recycledproducts

Buy and use products in their non-aerosolform.

Select products with less packaging.Packaging consumes energy when it ismade, generates harmful volatile organiccompounds when it is printed and

produces carbon dioxide & carbonmonoxide when its burned

Look for durability in products you buy &use , not just lower price.

R d d l d i


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Reduce, reuse and recycle used itemswhenever possible. Buy and use recycledproducts

Buy and use products in their non-aerosolform.

Select products with less packaging.Packaging consumes energy when it ismade, generates harmful volatile organiccompounds when it is printed and

produces carbon dioxide & carbonmonoxide when its burned

Look for durability in products you buy &use , not just lower price.

chapter 5-the air around us

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