GREEN
CHEMISTRY
KNOCKHARDY PUBLISHING
2008
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
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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?
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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
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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•
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•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
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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 •
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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 •
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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 •
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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 •
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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 •
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BAD
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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
©2009 JONATHAN HOPTON & KNOCKHARDY PUBLISHING