Unit 5: Atoms, purity and climate
Atmosphere and climate — HIA International - Grade 7 Revision Notes & Topical Questions
5 min read 10 parts Lesson 6 of 6 3 quizzes
Lesson summary
5.5 Atmosphere and climate — HIA INTERNATIONAL notes: Describe how the atmosphere has changed, how human activities affect it and ways to reduce global warming.Formation — the Earth formed about 4600 million years ago and was molten at first.Volcanoes — produced gases that formed…
- Composition about 4000 million years ago
- Temperature
- Unsuitable
- Water vapour
- Oxygen rise
- Photosynthesis
Part 1 of 8The early atmosphere
1Formation
- Formation the Earth formed about 4600 million years ago and was molten at first.
2Volcanoes
- Volcanoes produced gases that formed the early atmosphere, and water vapour condensed to form oceans.
3Composition about 4000 million years ago
- Composition about 4000 million years ago mainly carbon dioxide (about 95%), little or no oxygen, small amounts of methane and ammonia and some water vapour.
4Temperature
- Temperature above 400 °C, like Venus today.
5Unsuitable
- Unsuitable for animals, because it had no oxygen.
Part 2 of 8Atmosphere today
| Gas | Percentage |
|---|---|
| Nitrogen | About 78% |
| Oxygen | About 21% |
| Argon | About 0.9% |
| Carbon dioxide | About 0.04% |
1Water vapour
- Water vapour varies.
2Average surface temperature
- Average surface temperature about 20 °C.
Part 3 of 8How the atmosphere changed
Oxygen rise
- Oxygen rise about 3500 million years ago microorganisms used carbon dioxide and made oxygen.
Photosynthesis
- Photosynthesis carbon dioxide + water gives glucose + oxygen.
Evidence
- Evidence oxygen combined with iron in rocks to form red iron oxide.
Carbon dioxide falls
- Carbon dioxide falls by 200 million years ago very little remained because carbon was used to make living things.
Locked carbon
- Locked carbon in fossil fuels such as coal and oil, and in limestone formed from shelled animals made of calcium carbonate.
Carbon recycling
- Carbon recycling when organisms die and rot, carbon is released again.
Part 4 of 8Human changes to the atmosphere
Burning fossil fuels
- Burning fossil fuels carbon + oxygen gives carbon dioxide, in power stations, transport and industry.
Deforestation
- Deforestation fewer trees use less carbon dioxide in photosynthesis.
Cattle
- Cattle produce methane.
Cement making
- Cement making calcium carbonate gives calcium oxide + carbon dioxide.
Result
- Result carbon dioxide levels have risen for about 200 years.
Part 5 of 8Greenhouse effect and global warming
Greenhouse effect
- Greenhouse effect a natural effect where gases such as carbon dioxide, methane and water vapour trap heat like a blanket or greenhouse, keeping Earth warm.
Enhanced effect
- Enhanced effect more greenhouse gases mean less heat escapes, so the climate warms.
Global warming
Global warming the rise in the Earth's average temperature.
Analogy
Analogy a comparison that helps explain an idea, such as the blanket.
Effects
- Effects melting ice, rising sea levels, more extreme weather and changes to habitats.
Part 6 of 8Investigating the greenhouse effect
1
Place a thermometer in each of three plastic bottles without touching the sides.
2
Add extra carbon dioxide to one, about 5 cm of water to another, and leave the third with normal air.
3
Label them and place them outside or near a window.
4
Record the temperature in each at the start and at regular times over several days.
Control
- Control the bottle of normal air.
Result
- Result the bottles with extra greenhouse gas warm more.
Part 7 of 8Renewable resources
| Resource | How it is used | Problem |
|---|---|---|
| Wind | Turbines in wind farms generate electricity | Only works when the wind blows |
| Tidal | Water trapped behind a barrier turns turbines | Only at certain times; barrier can harm habitats |
| Solar | Photovoltaic cells change solar energy to electricity | Only when the Sun is shining |
Renewable resource
Renewable resource one that does not run out or can be replaced within a human lifetime.
Non-renewable resource
Non-renewable resource one that cannot be replaced after use, such as coal, petroleum and natural gas.
No carbon dioxide
- No carbon dioxide wind, tidal and solar generation produce no carbon dioxide.
Part 8 of 8Bioplastics
Bioplastics
Problem with conventional plastics
- Problem with conventional plastics made from petroleum and do not break down easily, so waste builds up in oceans and on land.
Bioplastic
Bioplastic a biodegradable material made from renewable sources such as vegetable oils, sawdust or food waste.
Benefit
- Benefit it reduces use of fossil fuels and damage from single-use plastics.
Key terms
| Term | Meaning |
|---|---|
| Atmosphere | The layer of gases around the Earth. |
| Greenhouse gas | A gas such as carbon dioxide or methane that traps heat. |
| Global warming | A rise in the Earth's average temperature. |
| Fossil fuel | A fuel such as coal or oil formed from ancient organisms. |
| Deforestation | Cutting down large areas of forest. |
| Renewable resource | A resource that does not run out. |
| Bioplastic | A biodegradable plastic made from renewable sources. |
| Analogy | A comparison used to explain an idea. |
Avoid these mistakes
1
Saying the early atmosphere was like today's — it was mainly carbon dioxide with no oxygen.
2
Saying the greenhouse effect is man-made — it is natural, only the increase is caused by humans.
3
Saying renewable energy works all the time — wind and solar depend on weather.
4
Saying the ozone layer causes global warming.
Marked practiceQuizzes for this lesson
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