Transcript 9G Environmental Chemistry - Prairie Rose School Division

KS3 Chemistry
9G Environmental
Chemistry
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Contents
9G Environmental Chemistry
Soil chemistry
Rocks and weathering
Acid rain
Greenhouse effect
Summary activities
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What is soil?
A layer of soil covers much of the
Earth’s surface. What is soil made
up of?
 weathered rock particles
 decaying remains of dead plants
and animals (called humus)
 water
 air
 living things, including plants
and animals such as worms
Plants need soil to grow. How does soil support plant growth?
Soil supplies plants with water and important nutrients and
also helps to anchor roots.
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How are soils different?
Soils in different areas are different.
What factors affect the composition
and properties of different soils?
 The weathered rock particles
come from different types of
rock and can vary in size.
 The amount of humus can vary
depending on the plants and
animals that lived in the soil.
 The amount of water in the soil is affected by the type of
rock particles. Clay particles are much smaller than sand.
A clay soil is heavier and contains more water than a
sandy soil which contains lots of room for air.
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pH of different soils
Different soils have different pHs.
Soils have different pHs because they
are made up of different rocks and so
contain different chemicals.
The pH of soil affects the availability of nutrients and plants
prefer to grow in soils of a certain pH. For example,
strawberries prefer acidic soil and plums prefer alkaline soil.
Why do farmers and gardeners need to check soil pH?
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Soil pH experiment
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Changing soil pH
If soil is too acidic to grow certain crops, lime can be added.
Lime is a base called calcium oxide.
What effect does lime have on the pH of soil?
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Changing soil pH
Farmers and gardeners can
choose only plants that prefer
the pH of their soil.
Alternatively, they can add
chemicals that change the
soil pH to suit the plants they
want to grow.
If soil is too acidic, lime (calcium oxide) is a base that can
be added.
The lime neutralizes the acid in the soil and so increases
the soil pH.
What type of chemical can be added if soil is too alkaline?
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Contents
9G Environmental Chemistry
Soil chemistry
Rocks and weathering
Acid rain
Greenhouse effect
Summary activities
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How do rocks change?
Rocks change over time due to
environmental conditions such
as temperature and acid rain.
The breakdown of rocks into
smaller fragments is called
weathering.
What are the three types of
weathering?
 Physical weathering – due to extremes of temperature
which can cause freeze-thaw or onion-skin weathering.
 Chemical weathering – due to chemical reactions
between substances in the rock and acidic rainwater.
 Biological weathering – due to the actions of plants
and animals.
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Physical weathering – freeze-thaw weathering
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Physical weathering – onion-skin weathering
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Contents
9G Environmental Chemistry
Soil chemistry
Rocks and weathering
Acid rain
Greenhouse effect
Summary activities
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What is acid rain?
Normal rainwater has a pH of about 5.6,
which means it is naturally slightly acidic.
This natural acidity is due to carbon
dioxide which dissolves in rainwater
and forms carbonic acid, a weak acid.
Rainwater with a lower pH than normal is called acid rain.
The burning of fossil fuels in power
stations and cars forms pollutants such
as sulfur dioxide and nitrogen oxides.
These gases dissolve in rainwater to
make sulfuric and nitric acids, which
are strong acids and so form acid rain.
Why is acid rain a serious environmental problem?
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Acid rain animation
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Effects of acid rain
Acid rain has many damaging effects on the environment:
 The strong acids in acid rain
speed up the chemical weathering
of rocks and buildings.
 Rivers, lakes and streams become
more acidic so that animals and
plants cannot live in them.
 Soil that becomes more acidic has
les nutrients so trees and other
plants cannot grow. Acid rain also
damages trees by breaking down
the waxy coating of leaves.
What can be done to reduce acid rain and its effects?
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Reducing acid rain
Governments are working to reduce the emission of acidic
pollutants caused by burning fossil fuels.
 Sulfur dioxide is formed when coal
containing sulfur is burned in power
stations.
This acidic pollutant can be removed
from the gases that are released to
the atmosphere.
 Nitrogen oxides are formed when
petrol burns in vehicle engines.
A car’s exhaust system can be fitted
with a catalytic converter which turns
harmful gases into harmless gases.
How do these changes help to reduce acid rain?
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Contents
9G Environmental Chemistry
Soil chemistry
Rocks and weathering
Acid rain
Greenhouse effect
Summary activities
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The greenhouse effect
The atmosphere is a thin layer of gases
that surrounds the Earth.
Certain gases in the atmosphere trap
some of the heat given off from Earth.
This trapped heat is reflected back to
the surface and warms the Earth.
The glass in a greenhouse also traps
heat inside and so the trapping of heat
by the Earth’s atmosphere is called
the greenhouse effect.
Without the atmosphere and the
greenhouse effect, Earth would be
too cold for life to exist!
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The greenhouse effect
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Global warming
Carbon dioxide is the main greenhouse
gas involved the warming of the Earth
by the greenhouse effect.
Human activity is producing more
carbon dioxide and other greenhouse
gases.
An increase in the amount of greenhouse gases could
increase the amount of heat trapped in the atmosphere.
Some scientists think that this increased greenhouse effect
is making the Earth warmer and leading to global warming.
What human activities might contribute to global warming?
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Effects of global warming
If global warming rises as some scientists
predict, it could cause major climate
changes:
 temperature – some areas may be
warmer, others colder;
 coastal flooding – sea levels could
rise as ocean’s get warmer;
 rainfall – some areas may be wetter and others drier;
 plants – some crops may be able to grow better and
others not at all.
Not all scientists agree about global warming. What evidence
is needed to support the theory about global warming?
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Contents
9G Environmental Chemistry
Soil chemistry
Rocks and weathering
Acid rain
Greenhouse effect
Summary activities
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Glossary
acid rain – Rainwater that is more acidic than normal
because acidic gases have dissolved in it.
humus – Soil material that is the decaying remains of
dead plants and animals.
global warming – The increased greenhouse effect that
some scientists think is causing climate change.
greenhouse effect – The warming of the Earth due to
the trapping of heat by certain gases in the atmosphere.
greenhouse gases – Gases, such as carbon dioxide
and methane, that are involved in the greenhouse effect.
nitrogen oxides – Pollutant gases that mainly come
from vehicle engines and form acid rain.
pollutant – A substance which damages the environment.
sulfur dioxide – A pollutant gas that mainly comes from
burning coal in power stations and forms acid rain.
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Anagrams
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Multiple-choice quiz
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