1. C HEMISTRY AS R EVISION Chains, Energy and Resources: Module 4

2. K EY W ORDS Greenhouse Effect; the process in which the absorption and subsequent emission of infrared radiation by atmospheric gases warms the lower atmosphere and the planet's surface Troposphere; lowest layer of atmosphere, extending from the Earth’s surface up to about 7km at the poles and 20 km in tropics Stratosphere; second layer of atmosphere. Contains ozone layer. 10 to 50km above surface Adsorption; process that occurs when a gas, liquid or solute is held to the surface of a solid, or a liquid

3. T HE G REENHOUSE E FFECT – G LOBAL WARMING IR radiation is absorbed by C=O, O-H and C-H bonds in H 2 O, CO 2 and CH 4, these absorptions contribute to global warming Greenhouse effect of a given gas is dependent on both its atmospheric concentration and its ability to absorb IR radiation The ability of a trace gas to cause global warming is its Global warming Potential. Related to the lifetime of the gas in the atmosphere Ability of the gas to absorb infrared radiation

4. S OLUTIONS TO THE G REENHOUSE E FFECT Alternative fuels Wind turbines, tidal power, solar panels, nuclear plants etc. Carbon Capture and Storage (CSS) Immediate strategy to remove waste Carbon Dioxide. Captured at source and stored away Stored in underground porous rock, old oil and gas fields Storage as carbonates Carbon Dioxide reacted with metal oxides to produce stable carbonates Required a lot of energy to do it

5. O ZONE L AYER Converts UV radiation into heat, making it warmer that other parts of the upper atmosphere Screens out UV c and most of UV b, a decrease in ozone would increase the amount of UV b. UV b causes sunburn, and genetic damage will can lead to skin melanomas O 2 molecules absorb high energy, short wavelength UV radiation, which splits the molecule. The O atoms then react with O 2 molecules to form ozone molecules, O 3. O 3 molecules then absorb UV radiation less than 310 nm converting them back into O 2 molecules and O atoms. The O then reacts with other O 2 molecules immediately. Chemical energy is released when O and O 2 combine as heat No net loss in Ozone

6. O ZONE D EPLETION Ozone depletion potential (ODP) Relative amount of breakdown to the ozone layer caused by a substance Compared with trichlorofluromethane, which has an ODP 1.0 Compounds disrupt the equilibrium between O 2 and O 3 CFCs are stable until subjected to UV radiation, where they break down, releasing Cl free radicals, which damage the ozone layer CFCl 3  Cl + CFCl 2 [initiation] Cl + O 3  ClO + O 2 [propagation] ClO + O  Cl +O 2 [propagation] O 3 + O  2O 2 [overall]

7. I NTERNAL C OMBUSTION E NGINE Emits Carbon Monoxide, Oxides of Nitrogen and unburnt hydrocarbons Carbon Monoxide Replace oxygen in Haemoglobin and cause oxygen depravation of the brain Oxides of Nitrogen Can be involved in the formation of low level ozone, which can harm the respiratory system of animals Often converted into nitric acid, a component of acid rain Unburnt hydrocarbons Form low level ozone.

8. C ATALYTIC C ONVERTER Made from platinum, rhodium and palladium supported on a honeycomb mesh, which provides a large surface area Hot exhaust gases pass over the catalytic surface and the harmful gasses are converted into less harmful products, which are then release into the atmosphere. Two types Oxidation; diesel engines, decrease emissions of CO and unburnt hydrocarbons Three way; petrol engines, NO + CO  carbon dioxide Catalyse provides a surface for reaction to take place CO and No gas molecules diffuse over catalytic surface, some molecules held by adsorption Temp bonds formed between catalytic surface and gas molecules Bonds hold the gas molecules in the correct position on the metal surface where they react together After reaction, carbon dioxide and nitrogen produced are desorbed from surface and diffuse away

9. G REEN C HEMISTRY Sustainability; development of processes that prevent the depletion of natural resources Improve our quality of life, make a profit and save the planet Designing processes with a high atom economy that minimise the production of waste materials Using renewable resources such as plant based substances Seeking alternative energy sources such as solar energy rather than consuming finite resources such as fossil fuels that will eventually be exhausted 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 Montreal Protocol to protect the ozone layer Stockholm Convention on Persistent Organic Pollutants to encourage governments to eliminate or reduce the release of toxic POPs