D.1 Primary Air Pollution

D.2 Ozone Depletion

D.3 Greenhouse Effect and Global Warming

D.4 Acid Rain

D.5 Water Suitable for Drinking

D.6 Dissolved Oxygen in Water

D.7 Water treatment

Extension Material HL Only

D.8 HL Smog

D.9 Ozone Depletion

D.10 Toxic Substances in Water

 

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D.1 Primary Air Pollution(3hr)

D.1.1 Describe the sources of carbon monoxide nitrogen oxides sulfur oxides particulate and hydrocarbons in the atmosphere.

• Include both natural and man-made sources. Balanced equations should be used where possible.

D.1.2 Outline the effects of primary pollution on health.

• Be familiar with at least one harmful effect of each of the substances in D.1.1.

D.1.3 Describe methods for the reduction of primary air pollution.

• CO catalytic converters
• NOx catalytic converters, lean burn engines, recirculation of exhaust gases
• SOx alkaline scrubbing, removal of sulfur-containing compounds from coal and oil, limestone-based fluidizeddbeds
• particulate electrostatic precipitation
• Hydrocarbons catalytic converters

D.2 Ozone Depletion (2hr) 

D.2,1 Describe the formation and depletion of ozone by natural processes.

• O₂ ---> 2O
• O₂ + O --> O₃
• O₃ --> O₂ + O
• O₃ + O --> 2O₂

D.2,2 List the pollutants, and their sources, that cause the lowering of ozone concentration.

• Consider CFCs and NOx

D.2.3 State the environmental effects ozone depletion.

• Include the increased incidence of skin cancer and eye cataracts, and the suppression of plant growth.

 D.2.4 Discuss the alternatives to CFC's in terms of their properties.

• Alternatives include hydrocarbons, fluorocarbons, and hydrofluorcarbons (HFCs). Include toxicity, flammability, the relative weakness of the C-Cl bond and the ability to absorb infrared radiation.

D.3 Greenhouse Effect and Global Warming (2hr) 

D.3,1 Describe the greenhouse effect.

D.3,2 List the main greenhouse gases and their sources, and discuss their relative effects.

• The greenhouse gases to be considered are CH₄, H₂O, CO₂, and N₂O, which have natural and man-made origins. Their effects depend on their abundance and their ability to absorb radiation

D.3.3 Discuss the influence of increasing amounts of greenhouse gases on global warming.

• Include climate change, thermal expansion of the oceans and melting of the polar caps

D.3.4 Outline the influence of particulate on the Earth's surface temperature.

• Particulate can lower the temperature by reflecting sunlight

D.4 Acid Rain (1.5hr) 

D.4.1 State what is meant by acid rain and outline its origins.

• Rain is naturally acidic because of dissolved CO₂; acid rain has a pH of less than 5.6
• Acid rain is caused by oxides of sulfur and nitrogen. Students should know the equations for the burning of sulfur and nitrogen and for the formation of H2SO3 and H₂SO₄

D.4.2 Discuss the environmental effects of acid rain and possible methods to counteract them. 

D.5 Water Suitable for Drinking (3hr)

D,5,1 Discuss the demand for fresh water and reasons for the inadequacy of its supply.

D.5.2 Compare the advantages and disadvantages of treating drinking water with chlorine and ozone.

D.5.3 Discuss ways to obtain fresh water from sea water using distillation, reverse osmosis and ion exchange

D.5.4 Discuss ways to reduce the amount of water used and to recycle water.

D.6 Dissolved Oxygen in Water (2hr)

D,6,1 Outline the importance of dissolved oxygen in water.

D.6.2 Outline biological oxygen demand (BOD) as a measure of oxygen-demanding wastes in water.

• refer to the amount of oxygen needed to decompose waste matter over a definite period of time. No distinction between biological and biochemical oxygen demand will be made.

 D.6.3 Distinguish between aerobic and anaerobic decomposition of organic material in water.

D.6.4 Describe the influence of sewage, detergents and fertilizers on the growth of aquatic plants, and the effect of their subsequent decomposition on oxygen concentration (eutrophication)

• The additional nitrogen and phosphorus compounds encourage growth of aquatic plants often in the form of algal blooms or in coastal areas "red tide"

D.7 Water treatment

D.7.1 Outline the primary and secondary stages of sewage treatment and state what is removed during each stage.

• For primary treatment, flocculation and sedimentation should be covered. For secondary treatment the use of oxygen and bacteria(eq activated sludge process)

D.7.2 Discuss the increasing use of tertiary treatment.

• Include the removal of heavy metals and phosphates by chemical precipitation and nitrates by chemical or biological processes.

D.8 HL Smog

D.8.1 Compare reducing and photochemical smog.

D.8.2 Describe the catalytic effect of particulate and nitrogen oxides on the oxidation of sulfur dioxide.

• particulate and SO₂ - heterolytic catalysis to form SO₃
• NO_x+ SO₃ free radical catalysis to for SO₃

D.8.3 Outline the steps involved in the formation of secondary pollutants in photochemical smog.

• Formation of radicals form the reaction of nitrogen oxides with sunlight and the reaction of these radicals with hydrocarbon, leading to the formation of aldehydes and peroxyacylnitrates (PANs)

D.8.4 Discuss the formation of thermal inversions and their effects on air quality.

D.9 Ozone Depletion (2hr)

D.9.1 Explain the dependence of O2 and O3 dissociation on the wavelength of light.

• O₂ ---->2O 242 nm
• O₃--> O₂ + O 330 nm

D.9.2 Describe the steps in the catalysis of O₃ depletion by CFC's and NOx

• CCl₂F₂ --> CClF₂+ Cl
• Cl + O₃--> ClO + O₂
• ClO + O --> O₂+ Cl
• NOx similar pathway

D.9.3 Outline the reasons for greater ozone depletion in the polar regions.

• Consider the seasonal variations in temperature in the upper atmosphere
• refer to surface catalysis on ice particles

D.9.4 Describe the properties required for sun screening compounds.

• Such compounds should contain conjugated double bonds,
• paraaminobenzoic acid PABA so that absorption of UV light is possible

D.10 Toxic Substances in Water (3hr)

D.10.1 Discuss the different approached in expressing toxicity

• include advantages and disadvantages of LD 50

D.10.2 State the principle toxic types of chemicals that may be found in polluted water

• Include heavy metals, pesticides, dioxins and polychlorinated biphenyls (PCBs)

D.10.3 Outline the sources, health and environmental effects of cadmium, mercury and lead.

• cadmium -metal plating, some rechargeable batteries, pigments
• mercury -seed dressing to prevent mold, batteries
• lead- some kinds of paint, tetraethyl lead in gasoline

D.10.4 Describe the sources and possible health effects of nitrated in drinking water.

• Include the formation of carcinogenic nitrosamines and a possible link to the formation of nitrites leading to oxygen depletion in the body

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