ObjectiveDiscuss some of the effects of these pollutants on health and on the environment:• the role of nitrogen dioxide and sulphur dioxide in the formation of ‘acid rain’ and its

effects on respiration and buildings.

KNOWING OUR RAIN!

Type of water

Pure water

Rainwater Acid rain

pH 7 5.6 4

FACTORY

houses

LAKE

1

2 and 3

4

5

ObjectiveDiscuss some of the effects of these pollutants on health and on the environment:• the role of nitrogen dioxide and sulphur dioxide in the formation of ‘acid rain’ and its

effects on respiration and buildings.

FACTORY

houses

LAKE

1

2 and 3

4

5

ObjectiveDiscuss some of the effects of these pollutants on health and on the environment:• the role of nitrogen dioxide and sulphur dioxide in the formation of ‘acid rain’ and its

effects on respiration and buildings.

1. Sulphur dioxide and nitrogen oxides gases are released into the air by factories and vehicles.The gases then react with air and water in the clouds to form ACID RAIN

FACTORY

houses

LAKE

1

2 and 3

4

5

ObjectiveDiscuss some of the effects of these pollutants on health and on the environment:• the role of nitrogen dioxide and sulphur dioxide in the formation of ‘acid rain’ and its

effects on respiration and buildings.

2. Sulphur dioxide reacts with air and water to form sulphuric acid.Chemical Equation:

2SO2 + O2 + 2H2O 2H2SO4

3. Nitrogen dioxide reacts with air and water to form nitric acid.Chemical Equation:

4NO2 + O2 + 2H2O 4HNO3

FACTORY

houses

LAKE

1

2 and 3

4

5

ObjectiveDiscuss some of the effects of these pollutants on health and on the environment:• the role of nitrogen dioxide and sulphur dioxide in the formation of ‘acid rain’ and its

effects on respiration and buildings.

4. The acid rain corrodes limestone buildings and metal structures.

5. Soils and lakes become too acidic.Acid rain kills fish.Acid rain leaches nutrients from soils and destroys plants.

ObjectiveDiscuss some of the effects of these pollutants on health and on the environment:• the role of nitrogen dioxide and sulphur dioxide in the formation of ‘acid rain’ and its

effects on respiration and buildings.

Sulphur dioxide and nitrogen oxides also cause irritation of the eyes

and breathing difficulties by

irritating the lungs

ObjectiveDescribe the reactions used in possible solutions to the problems arising from some of the pollutants • the use of calcium carbonate to reduce the effect of acid rain

Cure for ACID RAIN!The lakes contaminated by acid rain

can be neutralised by calcium hydroxide (limewater) or

calcium carbonate (limestone).

Objective

Prevention of ACID RAINPrevention is absolutely better than cure. But how do we make

it possible?• removing sulphur dioxide from waste gases (from removing sulphur dioxide from waste gases (from

industries and power stations) before they are released industries and power stations) before they are released into the air known as flue gas desulfurisation.into the air known as flue gas desulfurisation.

Describe the reactions used in possible solutions to the problems arising from some of the pollutants • flue gas desulphurisation

Sulphur dioxide is removed by reacting with calcium carbonate (or calcium oxide) to form calcium sulphite.

CaCO3 (s) + SO2 (g) CaSO3 (s) + CO2 (g)

The calcium sulphite is further oxidised to form calcium sulphate.

2CaSO3(s) + O2 (g) 2CaSO4 (s)

ObjectiveDescribe the reactions used in possible solutions to the problems arising from some of the pollutants • the redox reactions in catalytic converters to remove combustion pollutants.

Removal pollutants such as carbon monoxide and nitrogen oxides from car exhaust

This can be done by installing a catalytic converter in the vehicles

When the exhaust gases pass over the catalyst in the converter, a redox reaction occurs and the harmful pollutants are changed into harmless gases.

The carbon monoxide is oxidised to carbon dioxide and oxides of nitrogen reduced to nitrogen gas

2NO(g) + 2CO (g) N2 (g) + 2CO2 (g)CO + NO

CO2 + N2

Catalytic

Converter

Objective: Discuss the importance of ozone layer and the problems involved with the depletion of ozone by reaction with chlorine containing compounds, chlorofluorocarbon, (CFCs)

Ozone is an element with molecular formula O3. The ozone layer in the atmosphere acts as a shield to filter out the harmful uv radiation from the sun.

Importance of OZONE LAYER

If this harmful uv radiation is allowed to reach the surface of the earth, there would be an increase in

• skin cancer

• eye damage e.g. cataract

• genetic mutation

Ozone layer filters out harmful uv light

SUN

Objective: Discuss the importance of ozone layer and the problems involved with the depletion of ozone by reaction with chlorine containing compounds, chlorofluorocarbon, (CFCs)

What causes the depletion of ozone layer in the atmosphere?

Chlorofluorocarbons

CFCs

Objective: Discuss the importance of ozone layer and the problems involved with the depletion of ozone by reaction with chlorine containing compounds, chlorofluorocarbon, (CFCs)

1

2

3

4

Propellent from aerosols release CFCs into the atmosphere

CFCs reach the atmosphere where the ozone layer is found

In the presence of sunlight, CFCs decompose to form chlorine atoms

Chlorine atoms react with ozone moleculesin the ozone layer to form chlorine oxide and oxygen, thus destroying the ozone layer

5Ozone layer is destroyed

6Harmful uv light reaches earth through the holes in the ozone layer

Objective: Describes the carbon cycle in simple terms, to include combustion, respiration and photosynthesis

What is the carbon cycle?

The mechanisms that maintain the level of carbon dioxide in the atmosphere

Objective: Describes the carbon cycle in simple terms , to include combustion, respiration and photosynthesis and how carbon cycle regulates the amount of CO2 in the atmosphere

Atmospheric carbon dioxide

RespirationPhotosynthesis

Combustion of fuel

3 main processes in the carbon cycle that maintains the level of carbon dioxide in the air are:

Carbon dioxide is produced.

It is a process in which food taken in by living things are converted into carbon dioxide and water

C6H12O6 + 6O2 6CO2 + 6H2O

Carbon dioxide is produced

Carbon dioxide is removed.

During photosynthesis, green plants convert carbon dioxide and water into food (glucose) and oxygen in the presence of sunlight6CO2 + 6H2O C6H12O6 + 6O2 glucose

Objective: State that carbon dioxide and methane are greenhouse gases and may contribute to global warming

The earth’s surface is heated by radiation from the sun. Some gases in the air trap this heat radiation and prevent much of it from escaping into space. The energy retained in the atmosphere produces a warming effect known as the greenhouse effect. This leads to an increase in the earth’s temperature or global warming.

Solar radiation atmosphere

Some radiation escapes into space Some radiation absorbs

by the gases in the atmosphere

They are called greenhouse gases.

Examples : carbon dioxide & methane

Is the greenhouse effect important?Yes, without the greenhouse gases, the earth would

be too cold for life to exist. It is the excessive greenhouse gases that leads to global warming

Objective: State that carbon dioxide and methane are greenhouse gases and may contribute to global warming, give the sources of these gases

Deforestation – when trees grow, they absorb carbon dioxide during photosynthesis. If there are less trees, more carbon dioxide will remain in the atmosphere. In addition, when trees are burnt, carbon dioxide is also given off.

Reasons for increase in CO2 and methane in the atmosphere

Burning of carbon containing fuel in factories.

Bacteria decay of vegetation and wastes produce methane gas

Objective: State that carbon dioxide and methane are greenhouse gases and and discuss the possible consequences of an increase in global warming

rapid evaporation of water from the earth surface. When this happen, carbon dioxide dissolved in the ocean will be driven out into the atmosphere.

Effects of increase in Global warming

a decrease in crop yield worldwide. Areas covered by vegetation may become deserts.

melting of ice in the North and South Poles. Low lying countries will be flooded.