global warming
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© OUP: To be used solely in purchaser’s school or college
Global warming
Objectives:
*Describe the contribution of the greenhouse gases CO2 and CH4 to global warming
**Explain how air pollution by greenhouse gases causes global warming
Starter:
Name all the green house gases
CO2,Nitrogen oxides, CFCs, CH4,
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What is global warming?
Over the last few hundred years, the average temperature of the Earth’s oceans has been rising. This is global warming.
Why is this a problem?
Global warming increases the energy in the atmosphere, making it turbulent – more storms, more droughts, more floods.
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The greenhouse effect is a theory to explain why global warming is happening.
What about the greenhouse effect?
The world needs the greenhouse effect. Without it the Earth would be too cold for most organisms to live.
How does the greenhouse effect explain global warming?
In the atmosphere is a layer ofgreenhouse gases.
Light reaches us from the Sun. Some of it is absorbed by the Earth and warms it. Some is reflected back into space.
The Earth gives off infrared radiation because it has
been warmed by the Sun.
With more greenhouse gases, more infrared is
reflected back to the Earth, and it gets warmer
still.
Some infrared radiation is reflected back by the
greenhouse gases. This makes the Earth warmer than it would be without the greenhouse gases.
CO2
H2O, CO2CO2
CO2
H2O, CO2
H2O, CO2
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The key greenhouse gases
Do these gases act as greenhouse gases in the atmosphere? Answer ‘yes’ or ‘no’.
One of these gases in particular is on the rise, causing the ‘enhanced greenhouse effect’. Which gas?
What processes produce this gas?
A greenhouse gas is a gas in the atmosphere that reflects infrared radiation back to Earth.
gas greenhouse gas?
carbon dioxide
methane
CFCs
nitrogen oxide
yes
yes
yes
yes
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Acid rain
Objectives
*Describe the causes and effects of acid rain
**State the measures that can be taken to reduce acid rain
Starter:
Name the gases that cause acid rain
CO2,Nitrogen oxides, SO2,
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What is acid rain?
Rain is naturally slightly acidic. Why?
Because carbon dioxide in the air dissolves in the falling water to make carbonic acid.
carbon dioxide + water carbonic acid
So what’s acid rain?
It’s a term used for rain that is more acidic than normal.
Acid rain forms when acidic gases in the air dissolve in the rain. These gases come from burning fossil fuels.
normal rain acid rain
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Acid rain is more acidic than normal rain. But how does it compare with other acids?
How acidic is acid rain?
Match the pH to the substance.
pH 1 pH 2 pH 3 pH 4pH 6 pH 7
substance pH
unpolluted rain
car battery acid
acid rain from a polluted area
acid in your stomach
pure water
vinegar
pH 6
pH 2
pH 4
pH 1
pH 7
pH 3
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transport (cars, planes, trains, etc.)domestic (fires at home)generating electricityindustrial furnaces and boilersforest fires, volcanoes and other natural sources
What causes acid rain?
All of these processes produce acidic gases which cause acid rain.
Rank them in order, starting with the worst offender.
1. generating electricity2. transport (cars, planes, trains, etc.)3. industrial furnaces and boilers4. forest fires, volcanoes and other natural sources5. domestic (fires at home)
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Meet the acid gases
The main acidic gases are: • sulphur dioxide (SO2) • nitrogen oxides (N2O, NO, NO2)
Acidic gases in the air can cause lung problems.
Roughly how many extra deaths occurred from the 5th to the 9th of December?
Is it fair to say that acid gases caused these deaths?
deaths per day
sulphur dioxideconcentration
date, December 1952
dea
ths
per
day/
sulp
hur
diox
ide
(p
pb)
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How is acid rain formed?
Acid rain can fall many miles from the source of the pollution.
What problems does acid rain cause?
Burning fuels release acidic gases, mainly sulphur
dioxide (power stations) and oxides of nitrogen (vehicles).
Acid gases rise in the air.
Acid gases react together in the clouds – sunlight
encourages this reaction.
Dry deposition – acid particles fall to the
ground in dust.
Falling rain dissolves the acidic gases.
Acid rain falls to the ground. It
makes soil, lakes and rivers more
acidic.
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It takes a while...
But acid rain is dangerous because it acts over many years.
And because the changes from day to day are small, people do not notice them.
Why does this make it even more dangerous?
Acid rain is a dilute acid solution. The acid in your stomach is stronger and more corrosive.
Think how much rain falls on a building over 200 years!
Even a slight increase in the acidity of rain could have serious effects over this timescale.
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But the effects are serious
Acid rain reacts to dissolve away rocks such as limestone. This destroys valuable buildings.
It makes rivers and lakes more acidic. This causes problems on moors and mountains where the ground is already acidic.
It allows poisonous chemicals such as aluminium salts to dissolve in water and soil. They poison trees and fish.
It reduces the growth of plants, including food crops.
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Is pollution getting worse – or better?
Hope or horror?
3719 64601188 8754854
Try to match the year to the amount of acidic gas produced. We’ve added a guess for 2010.
If you drew a graph of this data, what would it look like?
Can you explain this trend?
year thousand tonnes of SO2 produced in UK
1970
1980
1990
2000
2010
6460
4854
3719
1188
875
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_______ dioxide and nitrogen oxides are ______ gases released when _______ fuels are burnt. When they _________ in rainwater they make weak acids. Sulphur dioxide forms _________ acid and nitrogen oxides form ______ acid. Acid rain can make _____ too acidic for plants to grow. It can also make _______ and lakes too acidic for _____ to live in.
SULPHUR ACIDIC
FOSSILDISSOLVE
SULPHURIC
NITRICSOIL
RIVERSFISH
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Technology to combat acid rain:
Low sulphur fuels
Flue gas desulphurisation
Catalytic converters
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Improvements in the technology of burning fuels
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A catalytic converter
catalytic converter
conventional
silencer
honeycomb structure
coated with Platinum or Palladium(catalyst)
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Flue gas
desulfurization
waste gases
from furnace
air
lime and water
cleaned gases
to chimney
calcium sulfate
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A hydrogen-fuelled
car
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Good news, bad news
So is the pollution problem getting better?Decide whether each headline is good news or bad news.
Levels of acidic gases in the atmosphere are falling.
We are using cars more and more.
Governments all over the world have agreed to cut emissions of acidic gases.
Modern devices are more energy-efficient than old ones.
We are developing more and more gadgets and devices that use energy.
What do you think? How could we do better?
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1. Sulphur dioxide is an acidic gas made by...
a) burning scrap metal
b) burning fossil fuels
c) cows as they digest grass.
2. Acid rain is caused by...
a) acidic gases in the atmosphere dissolving in falling rain
b) ozone in the atmosphere dissolving in falling rain
c) increased sunlight.
Quiz
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3. The best way to reduce acid rain is by...
a) releasing alkaline gases into the air
b) pushing rain clouds out to sea with jet engines
c) reducing the production of acidic gases.
4. Which of the following is NOT caused by acid rain?
a) damage to buildings made of limestone
b) damage to lakes in some highland areas
c) asthma.
Quiz
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1. Carbon dioxide contributes significantly to the greenhouse effect.
2. Plants tend to increase the greenhouse effect by giving out carbon dioxide.
3. The rise in carbon dioxide in the atmosphere is probably due to human activity.
4. Global warming is causing a hole in the ozone layer.
True or False?
True or false?
Yes, most scientists agree with this statement.
TRUE! Plants take in carbon dioxide during the day for photosynthesis, so they tend to reduce the greenhouse effect!
FALSE! Again, most scientists now accept this statement.
TRUE! CFCs are causing the hole in the ozone layer, which is letting more ultraviolet radiation reach us. This is not the same problem as global warming.
FALSE!
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