Chapter 20 : Atmosphere and Environment

Name: _________________________ ( ) Class: _____ Date: ____________

What you will learn in this chapter:(a) describe the volume composition of gases present in dry air as being approximately 79% nitrogen, 20% oxygen and the remainder being noble gases (with argon as the mainconstituent) and carbon dioxide(b) name some common atmospheric pollutants, e.g. carbon monoxide; methane; nitrogenoxides (NO and NO2); ozone; sulfur dioxide; unburned hydrocarbons(c) state the sources of these pollutants as

(i) carbon monoxide from incomplete combustion of carbon-containing substances(ii) nitrogen oxides from lightning activity and internal combustion engines(iii) sulfur dioxide from volcanoes and combustion of fossil fuels

(d) describe the reactions used in possible solutions to the problems arising from some of thepollutants named in (b)

(i) the redox reactions in catalytic converters to remove combustion pollutants(ii) the use of calcium carbonate to reduce the effect of ‘acid rain’ and in flue gas desulfurisation

(e) discuss some of the effects of these pollutants on health and on the environment(i) the poisonous nature of carbon monoxide(ii) the role of nitrogen dioxide and sulfur dioxide in the formation of ‘acid rain’ and itseffects on respiration and buildings

(f) discuss the importance of the ozone layer and the problems involved with the depletion ofozone by reaction with chlorine containing compounds, chlorofluorocarbons (CFCs)(g) describe the carbon cycle in simple terms, to include

(i) the processes of combustion, respiration and photosynthesis(ii) how the carbon cycle regulates the amount of carbon dioxide in the atmosphere

(h) state that carbon dioxide and methane are greenhouse gases and may contribute to globalwarming, give the sources of these gases and discuss the possible consequences of an increase in global warming

1. Composition of AirGas Composition by volume

NitrogenOxygen

1%

Separation of Air into its components- Air is first cooled and compressed into liquid. - Liquid air is then separated into its constituents (or fractions) by ________________________________________________________________

2. Air PollutionAir pollution is defined as the condition in which air contains __________________________________________________________________________________.

Common air pollutants:

Pollutants Major Sources Harmful Effects

(a) Carbon monoxide __________________________ of carbon-

containing substances eg. charcoal, wood, petrol, etc.

- Carbon monoxide reacts with _______________ in the blood to form __________________ so the haemoglobin cannot transport blood to the rest of the body.

- Cause headaches, fatigue,_______________________ or even death

(b) ______________________________(eg. nitrogen monoxide, NO & nitrogen dioxide, NO2.)

1) Reactions that occur in car engines ( ___________________________________)

2) From __________________

Nitrogen reacts with oxygen in the air to form nitrogen monoxide.N2 (g) + O2 (g) 2NO (g)

Nitrogen monoxide reacts with oxygen to form nitrogen dioxide (NO2).2NO (g) + O2 (g) 2NO2 (g)

1) _______________________

2) Breathingdifficulties

3) Lung inflammation (bronchitis)

4) Acid rain

(c) Sulfur dioxide

1) _________________________________________________________ (especially coal)

2) ________________________

Sulfur reacts with oxygen in the air to form sulfur dioxide.S (g) + O2 (g) 2SO2 (g)

3. Other air pollutants(a) ________________________ (b) ___________________________(c) ________________________

_________________________ are released in car exhaust. _____________________ is a colourless and odourless gas produced when plant

and animal matter decay. It is also produced from the decay of rubbish in landfills.

4. Effects of Air Pollution – Acid Rain• Rain usually has a pH that is slightly below 7. • Why? ________________________________________________________• However, acid rain has a pH value of 4 or less.

(a) Formation of acid rain

Acid rain is formed when acidic air pollutants such as __________________(SO2) and ___________________________ (NO2) dissolve in rainwater.

• Sulfur dioxide dissolves in water to form ________________________ (H2SO3).

Chemical equation: _________________________________________________In the presence of oxygen in the air, acid is slowly oxidised to sulphuric acid

(H2SO4).

• In the presence of oxygen and water, nitrogen dioxide is converted to

________.

Chemical equation: _________________________________________________ (b) Effects of Acid Rain

acid corrodes buildings and

metal structures

soils acidified

acid kills fish

lakes acidified

acid damages trees through

roots

gases damage green leavessulphuric acid nitric acid

ACID RAIN

gases react with air and water in clouds

coal, oil, fossil fuels burned

• ______________________________________ such as fences and bridges• Reacts with ______________________ in marble and limestone. • ______________________ value of natural water bodies to below 4, which will

_________________________________________ • _______________________________ from the soil and destroys plants.

(c) Reducing effects of Acid Rain(i) Catalytic converters

o Attached to the exhaust system of a car. o Contains catalysts - platinum and rhodium.o Catalytic converters involve the use of __________________________ to

remove air pollutants: __________________________ is oxidised to carbon dioxide.

___________________________ are reduced to nitrogen.Eg. Nitrogen monoxide + carbon monoxide nitrogen + carbon dioxide Chemical equation: ________________________________________

______________________________________ are oxidised to carbon dioxide and water.

Eg. Octane + oxygen carbon dioxide + water vapour 2 C8H18 (g) + 25 O2 16 CO2 (g) + 18 H2O (g)

(ii) Flue Gas Desulfurisation 2 ways of minimising the effects of sulphur dioxide pollution: • _____________________ from fossil fuels before burning. However, this method

is too expensive and difficult.• Remove ___________________ from _____________(flue gases) from burning.

- Process known as desulfurisation o Sulfur dioxide reacts with an aqueous suspension of _________________

to form solid ______________________________.CaCO3(s) + SO2(g) CaSO3(s) + CO2(g)

o The calcium sulfite is further oxidised to _________________________ by atmospheric oxygen.CaSO3(s) + O2(g) 2CaSO4(s)

5. Control of Air Pollution in Singapore• __________________ of the use of open __________for the disposal of

domestic and industrial wastes• Introduction of _____________________ and phasing out of leaded petrol• ________________ of the permissible level of ______________ in diesel • Fitting of all petrol-driven vehicles with ___________________________

6. Depletion of the Ozone Layer • Ozone is a bluish, very reactive gas, whose molecule is made by

_____________________________. (O3)• At low altitudes, it can cause breathing difficulties and photochemical

smog.• However, in the stratosphere, the ozone layer shields us from

_______________________________________________________.Note: UV radiation can cause skin cancer, genetic mutations and

cataracts.

• What is causing the depletion of ozone in the stratosphere?___________________________________________________________Note: CFCs are compounds containing the elements carbon, fluorine &

chlorine. They are widely used as ________________________________________ and as _________________________ in refrigerators and air conditioners.

• How do CFCs destroy the ozone layer?- Propellants in aerosols and coolants from refrigerators release

______________ into the atmosphere.- CFCs reach the stratosphere where the protective layer is found.- In the presence of sunlight, CFCs decompose to form ________________.- Chlorine atoms react with __________ molecules in the

stratosphere to form ____________________________, thus destroying the ozone layer.

• What is being done to the problem of ozone depletion?___________________________________________________________

7. The Carbon Cycle ___________________________________________________________is called the

carbon cycle. Processes that produce carbon dioxide:

(a) ______________________: During respiration, carbon and hydrogen compounds in food are converted into ______________ and _____________. C6H12O6(aq) + 6O2(g) 6CO2(g) + 6H2O(l) + energy (b) ________________________________Most fuels contain both carbon and hydrogen. When these fuels are burnt, _____________________ and ________________are produced.CH4(g) + 2O2(g) CO2(g) + 2H2O(l)Heat energy is also given off.

Processes that remove carbon dioxide (a) ______________________________During photosynthesis, green plants convert carbon dioxide and water

into glucose and oxygen in the presence of sunlight.

6CO2(g) + 6H2O(l) C6H12O6(aq) + 6O2(g)

8. (a) The Greenhouse Effect Greenhouse gases allow the visible radiation from the sun to reach the

Earth’s surface but ___________________________________________ which is emitted by the Earth. This produces a _______________________ called the greenhouse effect.

Carbon dioxide is one of the main greenhouse gases. Besides carbon dioxide, what are the other types of greenhouse gases?___________________________________________________________

8. (b) Global warming Greenhouse gases, such as carbon dioxide, are building up rapidly in the

atmosphere. Why is that so? ________________________________________________________________________________________________

• Therefore, carbon dioxide is being added to the atmosphere at a higher rate than photosynthesis can remove the excess gas.

• The effect of carbon dioxide build-up is an ____________________________________________________________________ global warming

• Consequences of Global warming.o a __________________________ world-wide because the areas that are

currently covered by vegetation may become deserts, o the ______________________________________ in the North Pole and

South Pole. This will cause the levels of oceans to rise and _______ low-lying countries such as the Netherlands.

o the ____________________________ from the Earth’s surface. When this happens, carbon dioxide dissolved in the oceans will be driven out into the atmosphere. This adds further to the greenhouse effect.

What questions do you have?

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