Transcript RevLessAQA_GCSESciC1_7PPt

AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
Changes
in
the
Earth
Changes in the Earth and
and its
itsatmosphere
atmosphere
Hodder Education Revision Lessons
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
Overview 1
• The Earth and its atmosphere provide everything we need.
• The Earth has a layered structure consisting of the crust, the
mantle and a core.
• The surface of the Earth and its atmosphere have changed
since the Earth was formed and are still changing.
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
Overview 2
• The atmosphere has been much the same for the last
200 million years. It provides the conditions needed for
life on Earth.
• Recently, human activities have resulted in further changes
in the atmosphere.
How do you think life was formed?
There is more than one theory.
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The Earth’s crust 1
The Earth consists of a core, the mantle and the crust. It is
surrounded by the atmosphere.
The Earth’s crust and the upper part of the mantle are cracked
into a number of large pieces (tectonic plates).
How do we know this?
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The Earth’s crust 2
Convection currents in the Earth’s mantle are driven by heat
released by natural radioactive processes. These currents
cause the plates to move at relative speeds of a few centimetres
per year.
The movements can be sudden and disastrous. Earthquakes
and/or volcanic eruptions occur at the boundaries between
tectonic plates.
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The Earth’s crust 3
What evidence is there for tectonic plates?
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
Formation of the Earth
Why is the core composed of iron and nickel?
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The Earth’s atmosphere 1
For 200 million years, the proportions of different gases in the
atmosphere have been much the same as they are today:
• about four-fifths (80%) nitrogen
• about one-fifth (20%) oxygen
• small proportions of various other gases, including carbon
dioxide, water vapour and noble gases.
What produced the oxygen gas?
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The Earth’s atmosphere 2
There are several theories about how the atmosphere was
formed. One theory suggests that during this period the Earth’s
atmosphere was mainly carbon dioxide and there would have
been little or no oxygen gas (like the atmospheres of Mars and
Venus today).
There may also have been water vapour and small proportions
of methane and ammonia.
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The Earth’s atmosphere 3
During the first billion years of the Earth’s existence there was
intense volcanic activity. This activity released the gases that
formed the early atmosphere and water vapour that condensed
to form the oceans.
Look at the diagram sequence on the next three slides. What
happened to the methane and ammonia?
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The Earth’s atmosphere 4
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The Earth’s atmosphere 5
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The Earth’s atmosphere 6
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
Life on Earth
There are many theories as to how life was formed billions of
years ago. Plants produced the oxygen that is now in the
atmosphere.
Methane and ammonia burnt in this oxygen producing more
water, carbon dioxide and nitrogen.
Most of the carbon from the carbon dioxide in the air gradually
became locked up in sedimentary rocks as carbonates and fossil
fuels.
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
Carbon dioxide and the oceans
The oceans also act as a reservoir for carbon dioxide but
increased amounts of carbon dioxide absorbed by the oceans
has an impact on the marine environment due to an increase in
acidity.
Why does carbon dioxide make the ocean more acid and why
does this affect marine life?
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
Burning fossil fuels
Nowadays, the release of carbon dioxide by burning fossil fuels
increases the level of carbon dioxide in the atmosphere. Explain
the patterns shown in the table.
Year
Concentration of CO2 in
Average global
Global
the atmosphere (% by
temperature
population
volume)
(C)
in millions
1750
0.0278
13.3
350
1800
0.0282
13.4
500
1850
0.0288
13.4
1000
1900
0.0297
13.6
1500
1950
0.0310
13.8
3000
2000
0.0368
14.4
5500
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The gases in air
Air is a mixture of gases with different boiling points. It can be
fractionally distilled to provide a source of raw materials used in
a variety of industrial processes.
Gas
Boiling point (C)
Nitrogen
–196
Oxygen
–183
Argon
–186
Carbon dioxide
Helium
What are these gases used for?
Sublimes at –78
–269
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