Transcript Green Chemistry

RESOURCES
AS Level
LEARNING OUTCOMES
• Explain that infrared radiation is absorbed by
C=O, O–H and C–H bonds in CO2, H2O and
CH4, and this contributes to global warming.
• Explain that the greenhouse effect of a given
gas is dependent both on its atmospheric
concentration and its ability to absorb infrared
radiation.
THE GREENHOUSE EFFECT DEFINITION
THE GREENHOUSE EFFECT
energy from the sun is in the
ultra violet, visible and infra
red regions
47% reaches the earth
radiation re-emitted from the
earth is in the infra red region
70% of the radiation
returns to space
greenhouse gases
absorb the remainder
energy is returned to earth to keep it warm
Carbon
dioxide and
water
molecules will
vibrate as
energy is
absorbed
GREENHOUSE GASES
Different covalent bonds have different strengths due to the
masses of different atoms at either end of the bond. As a result,
they vibrate at different frequencies (imagine two balls on either
end of a spring) . The frequency of vibration can be found by
detecting when the molecules absorb electro-magnetic radiation.
Various types of vibration are possible. Bending and stretching are
two examples and are found in water molecules. Each occurs at a
different frequency.
Symmetric
stretching
Bending
Asymmetric
stretching
GREENHOUSE GASES
Carbon dioxide also undergoes bending and stretching.
Bending in a carbon dioxide molecule
DETECTING GREENHOUSE GASES
The frequencies lie in the INFRA RED part of the electromagnetic
spectrum and can be detected using infra red spectroscopy.
An infra red spectrum of atmospheric air
H2O
CO2
CO2
.
H2O
THE GREENHOUSE EFFECT SUMMARY
1.
2.
3.
4.
The Earth receives most
of its energy in the form of
electromagnetic radiation
from the Sun. (Most from
visible, some from UV and
IR regions).
The incoming radiation is
relatively unaffected by the
gases in the Earth’s
atmosphere.
Most IR radiation goes
back into space, however
certain gases absorb this
radiation, some is reemitted back towards the
Earth.
This traps the heat in the
lower atmosphere.
THE GREENHOUSE EFFECT
The greenhouse effect creates an
equilibrium.
The atmospheric gases absorb energy at
the same rate it radiates it, thus
maintaining a steady temperature.
GREENHOUSE GASES
CARBON DIOXIDE
CO2
contains
C = O bonds
WATER VAPOUR
H 2O
contains
O - H bonds
METHANE
CH4
contains
C - H bonds
The ‘Greenhouse Effect’ of a given gas is
dependent on its...
• atmospheric concentration
• ability to absorb infrared radiation
THE THREE MAIN GREENHOUSE GASES
Water vapour – from evaporation of lakes and oceans.
Most abundant.
Carbon dioxide – produced by volcanic eruptions,
respiration of animals and burning or organic matter
(plants).
Methane – emitted
during the production of
fossil fuels, rotting waste
in landfill sites and
released from certain
animals (cows). Least
amount but greatest
contributor.
SO WHAT’S THE PROBLEM?
The greenhouse effect is a natural process,
keeping our planet at a temperature capable
of supporting life.
The problem: Human activity is producing
more greenhouse gases, which threaten to
upset this fine natural balance, resulting in
global warming.
GLOBAL WARMING POTENTIAL
(GWP)
• The ability of a trace gas to cause global
warming is described by its GWP.
• GWP is related to the lifetime of a gas in the
atmosphere as well as the ability of a gas to
absorb IR radiation.
• Since banning use of CFC’s their effect is
diminishing.
QUESTIONS
1. Name the three greenhouse gases
2. Outline the molecular processes that
enable heat to be kept close to the Earth.
3. What factors contribute to a gas’s
contribution to global warming?
CLIMATE
CHANGE
Learning objectives
• Explain the importance of controlling global
warming caused by atmospheric increases in
greenhouse gases.
• Outline the role played by chemists through the
provision of scientific evidence that global
warming is taking place.
• Understand the role of chemists in monitoring
progress of initiatives such a Kyoto protocol.
WHAT IS CLIMATE CHANGE?
• An increase in the concentration of greenhouse gases
leads to climate change / global warming.
• Global warming is defined as ‘an increase in the average
temperature of the Earth’s atmosphere, especially a
sustained increase big enough to cause climate change’
• What does this mean?
•The temperature goes up (warmer summers, mild winters)
•Plants and crops may not be able to grow in the same places
•Extreme storms, hurricanes and floods may become more common
•Sea levels may rise causing flooding
HOW DO WE FIND OUT IF GLOBAL WARMING
IS HAPPENING?
We need to record the
temperature and the weather at
lots of places across the Earth.
After many years, we can see a
pattern in the data.
Scientists try to decide what the
pattern means.
GLOBAL WARMING CAN BE SEEN IN:
• In the Arctic, ice and permafrost disappearing
• In the Antarctic, ice sheets melting into the oceans
• Tropical areas experiencing more frequent and
destructive storms and floods
• In Europe, glaciers are disappearing and there
have been extreme heat waves.
REDUCING GREENHOUSE EMISSIONS
• Earth Summit in 1992 – international agreement that
climate change must be prevented, but there was little
action.
• Kyoto Protocol – 0ver 100 countries. Countries must reduce
emissions of six greenhouse gases by 5% by 2012.
• USA – biggest emitter (25% of global emissions) – refused
to sign.
• Carbon emissions need to be reduced by 70-80%, even
with new wind turbines, etc.
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.
EU STRATEGY
In 2007 the EU agreed a strategy to fight
against global warming.
The deal set the following targets to be reached by
2020:
1. 20% of energy used in the EU will come from
renewable sources.
2. 10% of transport fuels will come from biofuels.
3. EU greenhouse emissions will be reduced to
20% below 1990 levels.
THE GREENHOUSE EFFECT
What can chemists do to minimise climate
change from global warming?
• provide scientific evidence to governments to
confirm it is taking place
• monitor progress against initiatives such as
the Kyoto protocol
• investigate solutions to environmental
problems
GOVERNMENTS LISTEN TO SCIENTISTS
• Politicians are now slowly believing what
scientists have been saying for years
“Human activity is contributing to global
warming”.
• Politicians are now looking for measures to
reduce carbon emissions.
• Kyoto Protocol and EU initiatives prove
governments are listening.
QUESTIONS
1. List three consequences of global warming for
the Earth.
2. Petrol contains a mixture of hydrocarbons,
including isomers of C8H18.
a) Write a balanced equation for the complete
combustion of C8H18 (assume petrol contains
just this).
b) Calculate the reduction in CO2 emission from
a car per km in 2012 (130g CO2 per km)
compared with 2005 (162g CO2 per km) by
volume.
LEARNING OUTCOMES
• Outline how chemists investigate solutions to
environmental problems, such as carbon
capture and storage (CCS).
• Understand the removal of waste carbon dioxide
as a liquid injected deep in the oceans.
• Outline carbon storage in deep geological
formations, by reaction with metal oxides to form
stable carbonate minerals.
CAPTURE AND STORAGE OF CO2
BENEATH THE NORTH SEA
CARBON DOXIDE CAPTURE & STORAGE
What is it?
• CO2 is collected from industrial processes and power
generation
• it is separated and purified
• it is then transported to a suitable long-term storage site
Storage possibilities
• gaseous storage in deep geological formations
• liquid storage in the ocean
• solid storage by reaction as stable carbonates
How can it help?
• could reduce CO2 emissions from power stations by 80%
• could be used to store CO2 emitted from fermentation
processes