The Atmosphere and Environment

Learning GoalsLearning Goals Students will describe the volume Students will describe the volume

composition of gases present in dry air composition of gases present in dry air as 79% nitrogen, 20% of oxygen and as 79% nitrogen, 20% of oxygen and the remainder being noble gases (with the remainder being noble gases (with argon as the main constituent) and argon as the main constituent) and carbon dioxide.carbon dioxide.

AirAirMixture of gasesMixture of gases

Composition of airComposition of airDry clean air :Dry clean air :

79% nitrogen79% nitrogen20% oxygen20% oxygenRemainder being noble gases Remainder being noble gases

(with (with argon as the main constituent) argon as the main constituent) and carbon dioxide and carbon dioxide

Water vapour - variableWater vapour - variable

Fractional distillation of liquid airFractional distillation of liquid air

Dust free air is pumped into the plantDust free air is pumped into the plant

Carbon dioxide is removed by bubbling through an Carbon dioxide is removed by bubbling through an alkalialkali

NaOH(aq) + CONaOH(aq) + CO22(g) (g) → → NaNa22COCO33 (aq) + H (aq) + H22O (l)O (l)

Water is removed in a drying towerWater is removed in a drying tower

Gases are compressed to 200 atmGases are compressed to 200 atm

Expansion of gasesExpansion of gases

Repeated compression and expansion of Repeated compression and expansion of gases until temperature reaches -200gases until temperature reaches -20000CC

Liquid air to a fractionating towerLiquid air to a fractionating tower

Fractional distillation of liquid airFractional distillation of liquid air

AirAir

Cooling and Cooling and compressioncompression Liquid Liquid

airair

Fractional Fractional distillationdistillation

Nitrogen Nitrogen

bp -196bp -19600CC

Argon Argon bp -186bp -18600CC

OxygenOxygen

bp -183bp -18300CC

Components of liquid air and their Components of liquid air and their boiling pointsboiling points

gas Boiling point (0C)

xenonxenon -108-108

KryptonKrypton -152-152

OxygenOxygen -183-183

ArgonArgon -186-186

NitrogenNitrogen -196-196

neonneon -246-246

heliumhelium -269-269

Laboratory Preparation of oxygenLaboratory Preparation of oxygen

water

oxygen

Hydrogen peroxide

H2O2

& MnO2

2H2H22OO22 (aq) (aq) → O→ O22 (g) + 2H (g) + 2H22O (l)O (l)

Powdered manganese (IV) oxide is used as a catalystPowdered manganese (IV) oxide is used as a catalyst

Test for Oxygen gasTest for Oxygen gas

Oxygen Oxygen gasgas

Oxygen gas relights a Oxygen gas relights a glowing glowing splint.splint.

Uses of OxygenUses of Oxygen

1. Used in cylinders for life support : Hospitals ambulances Divers (mixture of oxygen and

helium) Astronauts Passenger aircraft carry oxygen

(high altitude; air pressure low; cabin is pressurised)


2. Rockets carry their own oxygen 2. Rockets carry their own oxygen for burning fuel; either liquid for burning fuel; either liquid oxygen or oxygen in compounds.oxygen or oxygen in compounds.

3. Making of steel – oxygen gas to 3. Making of steel – oxygen gas to burn off impuritiesburn off impurities


4. Oxy-acetylene flame – torch to 4. Oxy-acetylene flame – torch to weld iron and steel; cut metals weld iron and steel; cut metals (3500(350000C)C)

5. Treatment of sewage – oxygen 5. Treatment of sewage – oxygen

kills harmful bacteriakills harmful bacteria

Bunsen burner flameBunsen burner flame

Pale blue flame (non-luminous):Pale blue flame (non-luminous):(Complete combustion)(Complete combustion)

CHCH44 + 2O + 2O22 → CO→ CO22 + 2H + 2H22OO

Yellow flame (luminous flame)Yellow flame (luminous flame)(Incomplete combustion)(Incomplete combustion)

2CH2CH44 + 2O + 2O22 → 2CO + 4H → 2CO + 4H22OO

CHCH44 + O + O22 → C + 2H → C + 2H22OO

Reaction of certain metals with oxygenReaction of certain metals with oxygen

ElementElement EquationEquation pH in pH in solutionsolution

potassiumpotassium 4K(s) + O4K(s) + O22(g) (g) → 2K→ 2K22O (s)O (s) 13-1413-14

sodiumsodium 4Na(s) + O4Na(s) + O22(g) (g) → 2Na→ 2Na22O(s)O(s) 13-1413-14

magnesiummagnesium 2Mg(s) + O2Mg(s) + O22(g) (g) → 2MgO(s)→ 2MgO(s) 88

ironiron 3Fe(s) + 2O3Fe(s) + 2O22(g) (g) →Fe→Fe33OO44(s)(s) insolubleinsoluble

coppercopper 2Cu(s) + O2Cu(s) + O22(g) (g) → 2CuO (s)→ 2CuO (s) insolubleinsoluble

Properties of oxide in period 3Properties of oxide in period 3

GroupGroup II IIII IIIIII IVIV VV VIVI VIIVII

ElementElement NaNa MgMg AlAl SiSi PP SS ClCl

OxideOxide NaNa22OO MgOMgO AlAl22OO33 SiOSiO22 PP22OO55 SOSO22 ClCl22OO

BondingBonding ionicionic ionicionic IonicIonic covalentcovalent covalentcovalent covalentcovalent covalentcovalent

StateState solidsolid solidsolid solidsolid solidsolid solidsolid gasgas gasgas

naturenature basicbasic basicbasic amphoteriamphotericc

acidicacidic acidicacidic acidicacidic acidicacidic

Reaction of certain non-metals with Reaction of certain non-metals with oxygenoxygen

ElementElement EquationEquation pH in pH in solutionsolution

phosphoruphosphoruss

4P(s) + 5O4P(s) + 5O22(g) (g) → 2P→ 2P22O O 55(s)(s)

phosphorus pentoxidephosphorus pentoxide

Phosphoric acid Phosphoric acid

33

sulphursulphur S(s) + OS(s) + O22(g) (g) → SO→ SO22 (g) (g) Sulphurous acidSulphurous acid

33

carboncarbon C(s) + OC(s) + O22(g) (g) → CO→ CO22 (g) (g) Carbonic acidCarbonic acid

55

Learning GoalsLearning Goals Students will name some common Students will name some common

atmospheric pollutants listed below:atmospheric pollutants listed below: carbon monoxide, methane, nitrogen carbon monoxide, methane, nitrogen

oxides (NO, NOoxides (NO, NO22), ozone, sulfur dioxide, ), ozone, sulfur dioxide,

unburnt hydrocarbonsunburnt hydrocarbons

Learning GoalsLearning Goals Students will be able to state the Students will be able to state the

sources of pollutants assources of pollutants as CO: incomplete combustion of carbon-CO: incomplete combustion of carbon-

containing substancescontaining substances Nitrogen oxides: lightning activity and Nitrogen oxides: lightning activity and

internal combustion enginesinternal combustion engines Sulfur dioxide: volcanoes and combustion Sulfur dioxide: volcanoes and combustion

of fossil fuels, containing sulfur.of fossil fuels, containing sulfur.

Air PollutionAir Pollution

What is air pollution?What is air pollution?

Air that has Air that has chemicalschemicals that harm living that harm living things or damage non-living things.things or damage non-living things.

What are air pollutants?What are air pollutants?

Solid particles and poisonous gases in Solid particles and poisonous gases in the air.the air.

Air PollutantsAir Pollutants

1. Particulates1. Particulates 2. Carbon monoxide2. Carbon monoxide

3. Oxides of nitrogen3. Oxides of nitrogen 4. Sulphur dioxide4. Sulphur dioxide

5. Ozone & CFCs5. Ozone & CFCs 6. Unburnt hydrocarbon 6. Unburnt hydrocarbon

MethaneMethane

Photochemical smogPhotochemical smog

Air pollutantsAir pollutants

SourceEffects on health and environment

Prevention

7. Carbon cycle7. Carbon cycle

8. Greenhouse gases8. Greenhouse gases

Air PollutantsAir Pollutants

SourceSource : Where does it comes from? : Where does it comes from?

EffectsEffects : How does it affect the health of : How does it affect the health of people and the environment?people and the environment?

PreventionPrevention : What measures can be taken : What measures can be taken to stop that pollutant fromto stop that pollutant from coming into the air?coming into the air?

ParticulatesParticulates

Source :Source :i.i. Ground : earth moving eqiupment, Ground : earth moving eqiupment,

construction work and windconstruction work and windii.ii. Forest fires and volcanoesForest fires and volcanoes

Effect :Effect :i.i. Irritates the lungsIrritates the lungsii.ii. Produce haze (reduce visibility)Produce haze (reduce visibility)

ParticulatesParticulates

Prevention :Prevention :

Prohibition of the use of open fires for Prohibition of the use of open fires for the disposal of domestic and the disposal of domestic and industrial wasteindustrial waste

Carbon monoxideCarbon monoxide

Source :Source :

Incomplete combustion of Incomplete combustion of fuel/petrolfuel/petrol in motor vehicle engines.in motor vehicle engines.

Effect :Effect :

i)i) DangerousDangerous – it is colourless and – it is colourless and odourless, giving no warning to its odourless, giving no warning to its presence.presence.


Effect :Effect :

ii. ii. PoisonousPoisonous – CO is absorbed by – CO is absorbed by haemoglobin in the blood:haemoglobin in the blood:

Haemoglobin + CO Haemoglobin + CO → carboxyhaemoglobin→ carboxyhaemoglobin

This prevent the blood from This prevent the blood from transporting oxygen around the body.transporting oxygen around the body.


Effect :Effect :iii. At lower level – it causes headaches iii. At lower level – it causes headaches

fatigue and impaired judgement.fatigue and impaired judgement.

Prevention: Prevention: Motorcars fitted with Motorcars fitted with catalytic catalytic convertersconverters. Exhaust gases pass over a . Exhaust gases pass over a platinum and rhodium catalyst.platinum and rhodium catalyst.

2CO + O2CO + O22 → 2CO→ 2CO22

Sulfur dioxideSulfur dioxide

Source :Source :

i. Burning of coal and petroleum i. Burning of coal and petroleum

(fossil fuel)(fossil fuel)

S + OS + O22 → SO→ SO22

ii. Extraction of metalsii. Extraction of metals

iii. Volcanic eruptionsiii. Volcanic eruptions

Sulfur DioxideSulfur Dioxide

Effect :Effect :i. irritates the eye and attack lungs, i. irritates the eye and attack lungs,

causing breathing difficultiescausing breathing difficultiesii. Forms acid rainii. Forms acid rain

Sulfur dioxide reacts with oxygenSulfur dioxide reacts with oxygen and water in the air to form sulfuricand water in the air to form sulfuric acidacid

2SO2SO2 2 + O+ O22 + 2H + 2H22O O → 2H→ 2H22SOSO44

SOSO22 + H + H22O → HO → H22SOSO33

Sulfur DioxideSulfur Dioxide

Effects of acid rain:Effects of acid rain:

i.i. Corrodes Corrodes limestone/marblelimestone/marble buildings buildings and metal structuresand metal structures

ii.ii. It makesIt makes waterwater in lakes and riversin lakes and rivers acidicacidic, killing fish and other aquatic , killing fish and other aquatic life.life.

iii.iii. Acidic soilAcidic soil destroys trees and other destroys trees and other vegetation.vegetation.

Sulfur dioxideSulfur dioxide

Prevention Prevention

i.i. Remove sulfur from fossil fuels Remove sulfur from fossil fuels before burningbefore burning

- too expensive and technologically difficult- too expensive and technologically difficult

ii.ii. Flue gas desulfurisationFlue gas desulfurisation

- - removal of sulfur dioxide from waste removal of sulfur dioxide from waste gasesgases

Oxides of NitrogenOxides of Nitrogen

Source: Source: Car exhaust fumesCar exhaust fumesAt high temperature (in the car engine):At high temperature (in the car engine):NN22(g) + O(g) + O22 (g) (g) → 2NO (g)→ 2NO (g)

nitric oxidenitric oxide

More oxygenMore oxygen2NO(g) + O2NO(g) + O22 (g) → 2NO (g) → 2NO22 (g) (g)

Also occur during thunderstorms (lightning) Also occur during thunderstorms (lightning) and forest fires.and forest fires.

Oxides of NitrogenOxides of Nitrogen

Effects:Effects:Forms acid rain (nitric acid)Forms acid rain (nitric acid)

4NO4NO22(g) + 2H(g) + 2H22O(g) + OO(g) + O22 (g) (g) → 4HNO→ 4HNO33(aq)(aq)

Prevention:Prevention:Motor cars are fitted with Motor cars are fitted with catalytic catalytic converterconverter on the exhaust. on the exhaust.

2NO(g) + 2CO(g) → N2NO(g) + 2CO(g) → N22 (g) + 2CO (g) + 2CO22(g)(g)

Unburnt HydrocarbonUnburnt Hydrocarbon

Source:Source:

From petrol, octane CFrom petrol, octane C88HH1818

Insufficient oxygenInsufficient oxygen present or present or

insufficient timeinsufficient time in the cylinders for all in the cylinders for all the hydrocarbons to be burnt the hydrocarbons to be burnt completelycompletely

Unburnt HydrocarbonUnburnt Hydrocarbon

Effects:Effects:

Combine with Combine with nitrogen oxidesnitrogen oxides to form to form compounds responsible for compounds responsible for photochemical smogphotochemical smog..

Prevention:Prevention:

Design engines that use more oxygen Design engines that use more oxygen for combustion of the fuels.for combustion of the fuels.

New York

Beijing

Learning GoalsLearning Goals Students will be able to describe the Students will be able to describe the

reactions in possible solutions to the reactions in possible solutions to the problems arising from some of the problems arising from some of the pollutants.pollutants. the redox reaction in catalytic converters the redox reaction in catalytic converters

to remove combustion of pollutantsto remove combustion of pollutants The use of calcium carbonate to reduce The use of calcium carbonate to reduce

the effect of acid rain and in flue gas the effect of acid rain and in flue gas desulfurisation.desulfurisation.

Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.

Catalytic Converters Catalytic Converters

A catalytic converter is attached to the exhaust system of a car.

It contains the catalysts platinum and rhodium.



Metal- core converter



Ceramic - core converter

Reactions in Catalytic ConverterReactions in Catalytic Converter

The converter uses two different types The converter uses two different types of catalysts, a of catalysts, a reductionreduction catalyst and an catalyst and an oxidizationoxidization catalyst. catalyst.

The The reduction catalyst is the first stagereduction catalyst is the first stage of the catalytic converter. of the catalytic converter. It uses platinum and rhodium to help It uses platinum and rhodium to help

reduce the NOx emissions. reduce the NOx emissions. When an NO or NOWhen an NO or NO22 molecule contacts the molecule contacts the

catalyst, the catalyst rips the nitrogen atom catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, out of the molecule and holds on to it, freeing the oxygen in the form of Ofreeing the oxygen in the form of O22. .

Reactions in Catalytic ConverterReactions in Catalytic Converter

The The oxidation catalystoxidation catalyst is the second is the second stage of the catalytic converter. It reduces stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over monoxide by burning (oxidizing) them over a platinum and palladium catalyst. a platinum and palladium catalyst.

This catalyst aids the reaction of the CO This catalyst aids the reaction of the CO and hydrocarbons with the remaining and hydrocarbons with the remaining oxygen in the exhaust gas. oxygen in the exhaust gas.

Chemical Equations in Chemical Equations in Catalytic ConverterCatalytic Converter

Word Equation:Word Equation:

Nitric oxide + carbon monoxide Nitric oxide + carbon monoxide nitrogen + carbon dioxidenitrogen + carbon dioxide

2NO (g) + 2CO (g) 2NO (g) + 2CO (g) N N22 (g) + 2CO (g) + 2CO22 (g) (g)

Word Equation:Word Equation:Octane + oxygen Octane + oxygen carbon dioxide + carbon dioxide + water vapourwater vapour

2C2C88HH1818 (g) + 25O (g) + 25O22 (g) (g) 16CO 16CO22 (g) + (g) + 18H18H22O (g)O (g)


reactions in possible solutions to the reactions in possible solutions to the problems arising from some of the problems arising from some of the pollutants.pollutants. The use of calcium carbonate to reduce The use of calcium carbonate to reduce

the effect of acid rain and in flue gas the effect of acid rain and in flue gas desulfurisation.desulfurisation.

Flue Gas DesulfurisationFlue Gas Desulfurisation

The waste gases are called flue gases. The waste gases are called flue gases.

The process of removing sulphur dioxide The process of removing sulphur dioxide from flue gases is called desulphurisation.from flue gases is called desulphurisation.

Flue Gas DesulfurisationFlue Gas Desulfurisation

1.1. CaCOCaCO33(aq) + SO(aq) + SO22 (g) (g) → CaSO→ CaSO33(s) + CO(s) + CO22 (g) (g)

The calcium sulfite is oxidised to calcium The calcium sulfite is oxidised to calcium sulfate by air.sulfate by air.

2. 2CaSO2. 2CaSO33(s) + O(s) + O22 (g) → 2CaSO (g) → 2CaSO44 (s) (s)

Calcium oxide can also be used.Calcium oxide can also be used.

CaO(s) + SOCaO(s) + SO22(g) → CaSO(g) → CaSO33 (s) (s)

Learning GoalsLearning Goals Students will discuss the Students will discuss the

importance of ozone layer importance of ozone layer andand the problems involved with the the problems involved with the

depletion of ozone by reaction with depletion of ozone by reaction with chlorine containing compounds, chlorine containing compounds, chlorofluorocarbon (CFCs)chlorofluorocarbon (CFCs)

OzoneOzoneA pale blue almost colourless gas with a A pale blue almost colourless gas with a

characteristic smellcharacteristic smell

SourceSource

- electrical machines (photocopiers)- electrical machines (photocopiers)

- photochemical reaction - photochemical reaction

(a chemical reaction that is initiated by(a chemical reaction that is initiated by

sunlight or UV light, forming sunlight or UV light, forming

photochemical smog – hazy brown photochemical smog – hazy brown

air) air)

Ozone Ozone

EffectsEffects

High altitude : protects us from harmfulHigh altitude : protects us from harmful

UVUV

Low altitude : harmful (irritates eyes, Low altitude : harmful (irritates eyes,

chest and throat)chest and throat)- Form photochemical smog:Form photochemical smog:

Ozone Ozone

EffectsEffects- Form photochemical smog:Form photochemical smog:

NONO22 (g) + O (g) + O22(g) (g) ⇋ NO(g) + O(g) + O⇋ NO(g) + O(g) + O22(g)(g)

O(g) + OO(g) + O22(g) ⇋ O(g) ⇋ O33 (g) (g)

- Ozone can further combine with - Ozone can further combine with unburnt hydrocarbon to produce unburnt hydrocarbon to produce peroxyacyl nitrates (PAN)peroxyacyl nitrates (PAN) (cause (cause tearing of the eyes)tearing of the eyes)

Chlorofluorocarbon CFCsChlorofluorocarbon CFCs

Source:Source:

- Aerosal propellants- Aerosal propellants

- Coolant fluids in refrigerators and air - Coolant fluids in refrigerators and air conditioners and conditioners and

- Making expanded polystyrene - Making expanded polystyrene packagingpackaging

Chlorofluorocarbon CFCsChlorofluorocarbon CFCs

Effects:Effects:

- - How do CFCs destroy the ozone layer?How do CFCs destroy the ozone layer?

In the presence of sunlight, CFCs In the presence of sunlight, CFCs decomposed to form decomposed to form chlorine atomschlorine atoms..

- The chlorine atoms react with ozone - The chlorine atoms react with ozone molecules to form molecules to form chlorine oxidechlorine oxide and and oxygenoxygen..

Cl + OCl + O33 → ClO + O→ ClO + O22

Ozone layerOzone layer

A thin layer of ozone in the A thin layer of ozone in the stratosphere (20-50km) acts as a stratosphere (20-50km) acts as a shieldshield, , filtering out the filtering out the harmful UV raysharmful UV rays from from the sun.the sun.

The harmful radiation causes The harmful radiation causes skin skin cancer, genetic mutationcancer, genetic mutation and and eye eye damage (cataract)damage (cataract)


carbon cycle in simple terms, to carbon cycle in simple terms, to includeinclude The processes of combustion, respiration The processes of combustion, respiration

and photosynthesisand photosynthesis How the carbon cycle regulates the How the carbon cycle regulates the

amount of carbon dioxide in the amount of carbon dioxide in the atmosphere.atmosphere.

Carbon CycleCarbon Cycle

Atmospheric carbon dioxide

respiration photosynthesisCombustion / burning of fossil fuels + volcanic activity

Learning GoalsLearning Goals Students will be able to state that Students will be able to state that

COCO22 and CH and CH44 are greenhouse gases are greenhouse gases

and and may contribute to global warming, may contribute to global warming, give the sources of these gases and give the sources of these gases and discuss possible consequences of an discuss possible consequences of an

increase in global warmingincrease in global warming

The Greenhouse EffectThe Greenhouse Effect

Greenhouse gases:Greenhouse gases:- Carbon dioxide COCarbon dioxide CO22

- Methane CHMethane CH44

- Nitrous oxide NNitrous oxide N22O O

They absorb infrared radiation and thus They absorb infrared radiation and thus reduces the amount of heat energy reduces the amount of heat energy escaping into space escaping into space : : global warming.global warming.

MethaneMethane

Source:Source:

- - Bacterial decayBacterial decay of vegetable matter of vegetable matter

trapped in low-lying wetlands and trapped in low-lying wetlands and

stagnant water.stagnant water.

- - decaying dungdecaying dung and rubbishand rubbish buried in buried in

landfillslandfills

MethaneMethane

Effects:Effects:

- - In strong sunlight,In strong sunlight, methanemethane andand unburnt hydrocarbonsunburnt hydrocarbons can react withcan react with nitrogen dioxidenitrogen dioxide to formto form photochemical photochemical smog.smog.

- - Help trap heat from the sunHelp trap heat from the sun greenhouse effectgreenhouse effect or or global warmingglobal warming..

The Greenhouse EffectThe Greenhouse Effect

Effects:Effects:

- decrease in crop yield. (areas with - decrease in crop yield. (areas with vegetation may become deserts)vegetation may become deserts)

- floods due to melting of ice in North - floods due to melting of ice in North and South poles.and South poles.

- droughts resulting in food shortage.- droughts resulting in food shortage.

Water pollutionWater pollution

- Industrial wasteIndustrial waste- Untreated sewageUntreated sewage- FertilisersFertilisers- DetergentsDetergents- Litter Litter

9. Water pollution 10. Prevention of water pollution

Prevention of Water Prevention of Water pollutionpollution

- PurificationPurification- DesalinationDesalination- New waterNew water

The Atmosphere and Environment

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