Module 4: Resources


2.4 Module 4: Resources The emphasis here is on the application of chemical facts and principles to processes occurring in the environment and to the difficulties in providing solutions to pollution. It is important that candidates should appreciate this aspect, bearing in mind the increasing concern, both national and international, for protecting the environment and promoting 'Green Chemistry'.

2.4.1 Chemistry of the Air

* the 'Greenhouse Effect';

* the ozone layer;

* controlling pollution.

2.4.2 Green Chemistry

* sustainability.

Links AS Unit F322: Chains, Energy and Resources

* 2.1.2 Alkanes (radicals; combustion of fuels)

* 2.2.2 Halogenoalkanes (CFCs)

* 2.2.3 Modern Analytical Techniques

* 2.3.2 Rates and Equilibrium (reversible reactions; catalysts)

2.4.1 Chemistry of the Air

Context and exemplification Assessable learning outcomes

The 'Greenhouse Effect'

How Science Works 7a, 7c:

* Collecting data to confirm whether or not climate change is occurring; monitoring measures to abate the change; modelling the potential damage.

Candidates should be able to:

(a) explain that infrared radiation is absorbed by C=O, O-H and C-H bonds in H2O, CO2 and CH4, and that these absorptions contribute to global warming;

(b) explain that the 'Greenhouse Effect' of a given gas is dependent both on its atmospheric concentration and its ability to absorb infrared radiation;

(c) outline the importance of controlling global warming resulting from atmospheric increases in greenhouse gases;

(d) outline the role of chemists in minimising climate change resulting from global warming by:

  • (i) providing scientific evidence to governments to verify that global warming is taking place,
  • (ii) investigating solutions to environmental problems, such as carbon capture and storage, CCS, ie the removal of waste carbon dioxide as a liquid injected deep in the oceans, storage in deep geological formations, by reaction with metal oxides to form stable carbonate minerals,
  • (iii) monitoring progress against initiatives such as the Kyoto protocol;

The ozone layer How Science Works 6a, 6b:

  • * Benefits of use of CFCs and consequent breakdown of ozone layer.
  • * No specific equations will be required beyond this simple representation of this catalysis.

(e) explain that ozone is continuously being formed and broken down in the stratosphere by the action of ultraviolet radiation;

(f) using the chemical equilibrium, below: O2 + O . O3

  • (i) describe and explain how the concentration of ozone is maintained in the ozone layer, including the role of ultraviolet radiation,
  • (ii) outline the role of ozone in the absorption of harmful ultraviolet radiation and the essential benefit of this process for life on Earth;

(g) understand that radicals, eg from CFCs, and NOx from thunderstorms or aircraft, may catalyse the breakdown of ozone by the following simple representation: R + O3 „_ RO + O2 RO + O „_ R + O2 where R represents Cl¡E from a CFC or NO from nitrogen oxides;

Controlling air pollution

  • * No details are required of the chemical processes involved in formation of photochemical smog.
  • * Candidates should understand that bonding to the catalyst surface must be weak enough for adsorption and desorption to take place but strong enough to weaken bonds and allow reaction to take place.

(h) for carbon monoxide, oxides of nitrogen and unburnt hydrocarbons:

  • (i) explain their formation from the internal combustion engine,
  • (ii) state environmental concerns from their toxicity and contribution to low-level ozone and photochemical smog;

(i) outline how a catalytic converter decreases carbon monoxide and nitrogen monoxide emissions from internal combustion engines by:

  • (i) adsorption of CO and NO to the catalyst surface,
  • (ii) chemical reaction,
  • (iii) desorption of CO2 and N2 from the catalyst surface;

(j) outline the use of infrared spectroscopy in monitoring air pollution.

2.4.2 Green Chemistry

How Science Works 6a, 6b, 7c:

* The use of context case studies such as those below to demonstrate current principles of chemical sustainability; desirability of such processes economically and environmentally; appreciation that legislation may be required to enforce environmentally desirable processes; the inbuilt desirability from within the chemical community to clean up their act.

Context and exemplification Assessable learning outcomes

Sustainability Examples for (a) (not examinable):

  • * Lead has largely been eliminated from use in petrol, paints and electrical components.
  • * New foams such as PyrocoolR FEF have been invented to put out fires effectively without producing the toxic or ozone-depleting waste products found in other halogenated fire-fighting materials.
  • * Solvent-free reactions, ie use of reagent as solvent.
  • * For dry cleaning, liquid 'supercritical' CO2 can be used as a safer solvent than chlorinated hydrocarbons.
  • * Fossil fuels are being replaced or supplemented by renewable fuels, such as biodiesel, alcohol and fuel cells.
  • * Increased use of recycling of manufactured materials such as plastics, glass and metals.

Examples for (b) (not examinable):

  • * Production of biodiesel uses grain crops and land needed for food, with poorer countries being worse affected.

Examples for (c) (not examinable):

  • * Montreal Protocol on Substances that Deplete the Ozone Layer.
  • * Global Treaty on Persistent Organic Pollutants.
  • * Rio Declaration on Environment and Development.

Candidates should be able to:

(a) describe principles of chemical sustainability:

  • (i) using industrial processes that reduce or eliminate hazardous chemicals and which involve the use of fewer chemicals,
  • (ii) designing processes with a high atom economy that minimise the production of waste materials,
  • (iii) using renewable resources such as plant-based substances,
  • (iv) seeking alternative energy sources such as solar energy, rather than consuming finite resources such as fossil fuels that will eventually be exhausted,
  • (v) ensuring that any waste products produced are non-toxic, and can be recycled or biodegraded by being broken down into harmless substances in the environment;

(b) explain that the apparent benefits may be offset by unexpected and detrimental side-effects;

(c) explain the importance of establishing international cooperation to promote the reduction of pollution levels;

(d) discuss issues of sustainability in contexts based on the principles in a-c;

2.4.1 Chemistry of the Air

2.4.2 Green Chemistry