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AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
Hodder Education Revision Lessons
Changes in the Earth and its atmosphere
Changes in the Earth and its atmosphere
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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.
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How do you think life was formed?
There is more than one theory.
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?Click to
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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:
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• 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?
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.
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Why does carbon dioxide make the ocean more acid and why does this affect marine life?
AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
Burning fossil fuelsNowadays, 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.
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Year
Concentration of CO2 in
the atmosphere (% by
volume)
Average global
temperature
(C)
Global
population
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
AQA GCSE Science & Additional Science
Chemistry 1 Topic 7
The gases in airAir 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 Sublimes at –78
Helium –269
What are these gases used for?Click to
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