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GREEN CHEMISTRY KNOCKHARDY PUBLISHING 2015 SPECIFICATIONS KNOCKHARDY PUBLISHING GREEN CHEMISTRY INTRODUCTION This Powerpoint show is one of several produced to help students understand selected topics at AS and A2 level Chemistry. It is based on the requirements of the AQA and OCR specifications but is suitable for other examination boards. Individual students may use the material at home for revision purposes or it may be used for classroom teaching with an interactive white board. Accompanying notes on this, and the full range of AS and A2 topics, are available from the KNOCKHARDY SCIENCE WEBSITE at... www.knockhardy.org.uk/sci.htm Navigation is achieved by... either clicking on the grey arrows at the foot of each page or using the left and right arrow keys on the keyboard GREEN CHEMISTRY What is it? • encourages environmentally conscious behaviour • reduces and prevents pollution • reduces the destruction of the planet GREEN CHEMISTRY What is it? • encourages environmentally conscious behaviour • reduces and prevents pollution • reduces the destruction of the planet Basics • • • • • • • • • • • better to prevent waste than to treat it afterwards aim for maximum atom economy use processes which require fewer chemicals don’t make products that are toxic to human health don’t make products that are toxic to the environment reduce the energy requirements of processes use alternative energy resources use renewable raw materials, not finite resources use catalysts where possible waste products should be designed to be biodegradable reduce the risk of explosions and fires RECYCLING Definition “Recovering resources by collecting, separating, and processing scrap materials and using them as raw materials for manufacturing new products.” RECYCLING Definition “Recovering resources by collecting, separating, and processing scrap materials and using them as raw materials for manufacturing new products.” Why do it? • • • • • world resources are running out and are non-renewable we need to reduce the waste of valuable resources reduces the expense of disposal reduces expense of making things from raw materials avoids environmental problems posed by waste - landfill sites - greenhouse gases (mainly methane) - destroying habitats - de-forestation leading to climate change and the destruction of ecosystems RENEWABLE RESOURCES AND ENERGY RENEWABLE RESOURCES AND ENERGY Renewable resources • can be replenished by natural processes • their rate of replenishment is equal or greater than the rate of consumption • often do not contribute to global warming • often far more environmentally friendly • lead to more sustainable use of materials; resources can be used indefinitely RENEWABLE RESOURCES AND ENERGY Renewable resources • can be replenished by natural processes • their rate of replenishment is equal or greater than the rate of consumption • often do not contribute to global warming • often far more environmentally friendly • lead to more sustainable use of materials; resources can be used indefinitely Renewable energy • • • • • • plant-based substances such as wood solar energy tidal energy biomass hydro-electric power (HEP) wind power GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects. GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects. GOOD • created in 1928 as a non-toxic, non-flammable refrigerant • also used as solvents and in air conditioners • low reactivity and volatility GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects. GOOD • created in 1928 as a non-toxic, non-flammable refrigerant • also used as solvents and in air conditioners • low reactivity and volatility BAD • UV light in the upper atmosphere easily breaks the C-Cl bonds • free radicals formed speeded up the depletion of the ozone layer GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects. GOOD • created in 1928 as a non-toxic, non-flammable refrigerant • also used as solvents and in air conditioners • low reactivity and volatility BAD • UV light in the upper atmosphere easily breaks the C-Cl bonds • free radicals formed speeded up the depletion of the ozone layer CFC's break down in the presence of UV light to form chlorine radicals CCl2F2 —> Cl• chlorine radicals react with ozone O3 Cl• chlorine radicals are regenerated ClO• + + + •CClF2 —> ClO• + O2 O —> O2 + Cl• Overall, chlorine radicals are not used up so a small amount of CFC's can destroy thousands of ozone molecules before the termination stage. GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects. GOOD • created in 1928 as a non-toxic, non-flammable refrigerant • also used as solvents and in air conditioners • low reactivity and volatility BAD • UV light in the upper atmosphere easily breaks the C-Cl bonds • free radicals formed speeded up the depletion of the ozone layer CFC's break down in the presence of UV light to form chlorine radicals CCl2F2 —> Cl• chlorine radicals react with ozone O3 Cl• chlorine radicals are regenerated ClO• + + + •CClF2 —> ClO• + O2 O —> O2 + Cl• Overall, chlorine radicals are not used up so a small amount of CFC's can destroy thousands of ozone molecules before the termination stage. GREEN CHEMISTRY – EXAMPLES BIOFUELS • fuels made from a living things or the waste produced by them • renewable and potentially carbon neutral. GREEN CHEMISTRY – EXAMPLES BIOFUELS • fuels made from a living things or the waste produced by them • renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel. GREEN CHEMISTRY – EXAMPLES BIOFUELS • fuels made from a living things or the waste produced by them • renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel. ETHANOL GOOD GREEN CHEMISTRY – EXAMPLES BIOFUELS • fuels made from a living things or the waste produced by them • renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel. ETHANOL GOOD • • • • bio-ethanol is made from crops (corn and sugar cane) takes in carbon as carbon dioxide in the atmosphere when burnt, it returns CO2 to the atmosphere appears to be carbon neutral GREEN CHEMISTRY – EXAMPLES BIOFUELS • fuels made from a living things or the waste produced by them • renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel. ETHANOL GOOD • • • • BAD bio-ethanol is made from crops (corn and sugar cane) takes in carbon as carbon dioxide in the atmosphere when burnt, it returns CO2 to the atmosphere appears to be carbon neutral GREEN CHEMISTRY – EXAMPLES BIOFUELS • fuels made from a living things or the waste produced by them • renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel. ETHANOL GOOD • • • • BAD bio-ethanol is made from crops (corn and sugar cane) takes in carbon as carbon dioxide in the atmosphere when burnt, it returns CO2 to the atmosphere appears to be carbon neutral • energy is required to - plant and harvest - convert plants to ethanol • fertiliser and pesticides used are pollutants • crops compete for land with… crops / animals / forests • could destroy natural habitats and reduce biodiversity GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier. GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier. GOOD GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier. GOOD • • • • • • many are chemically inert non-toxic waterproof easy to mould non-biodegradable lightweight GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier. GOOD • • • • • • BAD many are chemically inert non-toxic waterproof easy to mould non-biodegradable lightweight GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier. GOOD • • • • • • BAD • • • • • many are chemically inert non-toxic waterproof easy to mould non-biodegradable lightweight made from crude oil which is a finite resource non-biodegradable so take hundreds of years to decompose can form toxic products during incineration a lot of energy is used in their formation disposal in landfill sites is - a waste of resources - environmentally unsound - takes up valuable space GREEN CHEMISTRY – EXAMPLES CATALYSTS • can be used to lower the energy required for a reaction to take place • can reduce the CO2 emissions from burning of fossil fuels • can give a better atom economy INTERNATIONAL CO-OPERATION KYOTO PROTOCOL (1997) INTERNATIONAL CO-OPERATION KYOTO PROTOCOL (1997) • over 50 developed countries pledged to cut greenhouse gas emissions • gases included carbon dioxide CO2 methane CH4 hydrofluorocarbons HFC’s perfluorocarbons PFC’s sulphur hexafluoride SF6 • some countries agreed to make larger cuts • developing countries were not required to cut emissions • the US didn’t sign up; it would have significantly affected their economy INTERNATIONAL CO-OPERATION KYOTO PROTOCOL (1997) • over 50 developed countries pledged to cut greenhouse gas emissions • gases included carbon dioxide CO2 methane CH4 hydrofluorocarbons HFC’s perfluorocarbons PFC’s sulphur hexafluoride SF6 • some countries agreed to make larger cuts • developing countries were not required to cut emissions • the US didn’t sign up; it would have significantly affected their economy But... Many experts say that the protocol is futile without US support as they are the world’s largest emitter of greenhouse gases. Countries such as India and China are going through great industrial change and they do not have to cut emissions. Cuts weren’t big enough according to many scientists, who say that a 60% cut is required to avoid the risks of global warming. GREEN CHEMISTRY THE END ©2015 JONATHAN HOPTON & KNOCKHARDY PUBLISHING