Topic 10 - Atmosphere and environment

10.1 Air

(a) describe the volume composition of gases present in dry air as 78% nitrogen, 21% oxygen and the remainder being noble gases (with argon as the main constituent) and carbon dioxide

(b) describe the separation of oxygen, nitrogen and the noble gases from liquid air by fractional distillation

(c) state the uses of oxygen (e.g. in making steel; oxygen tents in hospitals; in welding)

(d) name some common atmospheric pollutants (e.g. carbon monoxide; methane; nitrogen oxides (NO and NO₂); ozone; sulfur dioxide; unburned hydrocarbons)

(e) state the sources of these pollutants as

• (i) carbon monoxide from incomplete combustion of carbon-containing substances
• (ii) methane from bacterial decay of vegetable matter
• (iii) nitrogen oxides from lightning activity and internal combustion engines
• (iv) ozone from photochemical reactions responsible for the formation of photochemical smog
• (v) sulfur dioxide from volcanoes and combustion of fossil fuels
• (vi) unburned hydrocarbons from internal combustion engines

A presentation done by students of grade 11.

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

• (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

Another presentation done by students of grade 11

(g) 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 its effects on respiration and buildings

(h) discuss the importance of the ozone layer and the problems involved with the depletion of ozone by reaction with chlorine-containing compounds, chlorofluorocarbons (CFCs)

(i) *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

Here is a presentation done by students of grade 11.

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

10.2 Water

(a) state that water from natural sources contains a variety of dissolved substances

• (i) naturally occurring (mineral salts; oxygen; organic matter)
• (ii) pollutant (metal compounds; sewage; nitrates from fertilisers; phosphates from fertilisers and detergents; harmful microbes)

(b) discuss the environmental effects of the dissolved substances named in (a)

• (i) beneficial, e.g. oxygen and mineral salts for aquatic life
• (ii) pollutant, e.g. hazards to health; eutrophication

Here is another presentation by grade 11 students.

(c) outline the purification of the water supply in terms of

• (i) filtration to remove solids
• (ii) use of carbon to remove tastes and odours
• (iii) chlorination to disinfect the water

(d) state that seawater can be converted into drinkable water by desalination

Topic 5 - Energy From Chemicals

(a) describe the meaning of enthalpy change in terms of exothermic (ΔH negative) and endothermic (ΔH positive) reactions
Please read p302-303

(b) *represent energy changes by energy profile diagrams, including reaction enthalpy changes and activation energies (see 6.1(c))

Please read p309-311

(c) describe bond breaking as an endothermic process and bond making as an exothermic process

Please read p306-307

(d) *explain overall enthalpy changes in terms of the energy changes associated with the breaking and making of covalent bonds

Please read p307-309

(e) describe combustion of fuels as exothermic, e.g. wood, coal, oil, natural gas and hydrogen

Please read p311

(f) describe hydrogen, derived from water or hydrocarbons, as a potential fuel for use in future, reacting with oxygen to generate electricity directly in a fuel cell (details of the construction and operation of a fuel cell are not required) and discuss the advantages and disadvantages of this

Please read p313

(g) name natural gas, mainly methane, and petroleum as sources of energy

Please read p311

(h) describe petroleum as a mixture of hydrocarbons and its separation into useful fractions by fractional distillation

Please read p381-382

(i) name the following fractions and state their uses

• (i) petrol (gasoline) as a fuel in cars
• (ii) naphtha as feedstock for the chemical industry
• (iii) paraffin (kerosene) as a fuel for heating and cooking and for aircraft engines
• (iv) diesel as a fuel for diesel engines
• (v) lubricating oils as lubricants and as a source of polishes and waxes
• (vi) bitumen for making road surfaces

Please read p382

(j) describe photosynthesis as the reaction between carbon dioxide and water in the presence of chlorophyll, using sunlight (energy) to produce glucose and explain how this can provide a renewable energy source.

Please read p371-372

Topic 8 The Periodic Table

8.1 Periodic trends
(a) describe the Periodic Table as an arrangement of the elements in the order of increasing proton (atomic) number
Please read p284
(b) *describe how the position of an element in the Periodic Table is related to proton number and electronic structure
(c) *describe the relationship between Group number and the ionic charge of an element 
(d) explain the similarities between the elements in the same Group of the Periodic Table in terms of their electronic structure

(e) describe the change from metallic to non-metallic character from left to right across a period of the Periodic Table Please read p285

(f) *describe the relationship between Group number, number of valency electrons and metallic/non-metallic character
Please read p286-287

(g) *predict the properties of elements in Group I, VII and the transition elements using the Periodic Table
Please read p289-293

8.2 Group properties

(a) describe lithium, sodium and potassium in Group I (the alkali metals) as a collection of relatively soft, low-density metals showing a trend in melting point and in their reaction with water
Please read p289-291

(b) describe chlorine, bromine and iodine in Group VII (the halogens) as a collection of diatomic non-metals showing a trend in colour, state and their displacement reactions with solutions of other halide ions

Please read p292-294

(c) describe the elements in Group 0 (the noble gases) as a collection of monatomic elements that are chemically unreactive and hence important in providing an inert atmosphere, e.g. argon and neon in light bulbs; helium in balloons; argon in the manufacture of steel

Please read p295-296

(d) describe the lack of reactivity of the noble gases in terms of their electronic structures

8.3 Transition elements

(a) describe the central block of elements (transition metals) as metals having high melting points, high density, variable oxidation state and forming coloured compounds

(b) state the use of these elements and/or their compounds as catalysts, e.g. iron in the Haber process; vanadium(V) oxide in the Contact process; nickel in the hydrogenation of alkenes, and how catalysts are used in industry to lower energy demands and hence are economically advantageous and help conserve energy sources