Download - 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
Arrangement of apparatus
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)
Arrangement of apparatus
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
Arrangement of apparatus
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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Properties of Oxygen and Carbon Dioxide
Effect on burningwooden splinter.
Oxygen Activity Carbon dioxide
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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Properties of Oxygen and Carbon Dioxide
Effect on lime water.
Oxygen Activity Carbon dioxide
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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Properties of Oxygen and Carbon Dioxide
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
Arrangement of apparatus
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
Arrangement of apparatus
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
Arrangement of apparatus
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
Arrangement of apparatus
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.