SC21 Flashcards
SC21c
1) Recall the names of significant greenhouse gases.
2) Describe the processes involved in the greenhouse effect.
3) Describe how human activity increases the concentration of greenhouse gases.
1) The gases in the atmosphere that absorb energy are called greenhouse gases, and include carbon dioxide (CO2), methane (CH) and water vapour (H₂O).
2) The greenhouse effect is a natural process that occurs when greenhouse gases in the atmosphere trap heat from the Sun, warming the Earth’s surface. This process is necessary for life on Earth, but an increase in greenhouse gas concentrations can lead to global warming and climate change.
3) Burning fossil fuels releases carbon dioxide. Deforestation releases carbon dioxide. Cattle farming releases methane.
SC21c
1) Evaluate the correlation between atmospheric carbon dioxide concentrations and fossil fuel use.
2) Evaluate the evidence for increased atmospheric greenhouse gas concentrations being part of the cause of global warming and climate change.
1) The extra carbon dioxide is causing an enhanced greenhouse effect, greater than would happen naturally. The concentration of carbon dioxide in the atmosphere has increased in the last 200 years. This correlates with an increase in the use of fossil fuels. The burning of fossil fuels releases carbon dioxide into the atmosphere. There is a correlation between the increase in atmospheric carbon dioxide concentration and temperature change - as the concentration of carbon dioxide has increased, the global average temperature has generally increased too.
2) Other human activities are causing an increase in the amounts of other greenhouse gases in the atmosphere. There is a correlation between the increase in atmospheric carbon dioxide concentration and temperature change - as the concentration of carbon dioxide has increased, the global average temperature has generally increased too.
SC21d
1) Suggest possible effects on the climate of increased levels of carbon dioxide and methane.
2) Describe how human activity leads to increased carbon dioxide levels.
3) Describe how human activity leads to increased methane levels.
1) The extra carbon dioxide is causing an enhanced greenhouse effect, greater than would happen naturally. There is a correlation between the increase in atmospheric carbon dioxide concentration, and temperature change. As the concentration of carbon dioxide has increased, the global average temperature has generally increased as well.
The climate describes the average weather over a long time and over a large area. The enhanced greenhouse effect is leading to climate change. The effects of this include: glaciers and polar ice melting, sea levels rising, rainfall changing, producing floods or droughts, habitats changing.
2) The increased burning of fossil fuels has released more carbon dioxide. Increased deforestation has reduced the amount of carbon dioxide being removed from the atmosphere by photosynthesis.
3) Methane is released into the atmosphere by human sources: rice cultivation, livestock farming, and decomposition in landfills.
SC21d
1) Describe the projected effects of climate change.
2) Describe how the potential harmful effects of climate change can be addressed and limited.
1) - Rising average global temperatures will cause ice at the South Pole and glaciers to melt. The extra water will raise sea levels, which will lead to increased flooding in some areas. Higher average temperatures will also result in a loss of ‘sea ice’ at the poles.
- Some animals may move away from their natural habitats to find cooler areas. Some animals and plants may become extinct if they cannot survive at warmer temperatures or find new places to live.
- As weather patterns change, some areas will become drier and others will become wetter. Scientists predict that there will be more extreme weather events (such as heavy rainfall, powerful storms and heat waves). These changes will affect wildlife and the growth of crops that people depend upon.
- As more CO, is released, more of this acidic gas will dissolve in seawater, lowering its pH. This can harm organisms living in the seas and oceans. Additionally, as ocean temperatures rise, it causes coral to push out the photosynthetic algae that live in their tissues. These algae provide the colour of coral and so coral ‘bleaching’ may occur.
2) Encouraging energy efficiency, creating financial incentives to reduce CO2 emissions, using more renewable energy, increasing research into new energy resources.
SC21a
1) Describe how the Earth’s early atmosphere was formed.
2) State the names and relative amounts of the gases found in the Earth’s early atmosphere.
3) Explain how the oceans are thought to have formed.
1) The gases that made up the Earth’s early atmosphere were released by volcanic eruptions.
2) The Earth’s early atmosphere is thought to have been mainly carbon dioxide, with smaller amounts of water vapour and other gases, and little or no oxygen.
3) About 4 billion years ago, the Earth cooled down. This caused water vapour in the atmosphere to condense to liquid water, which formed the oceans.
SC21a
Draw conclusions from evidence about the Earth’s early atmosphere.
The Earth’s early atmosphere is thought to have been mainly carbon dioxide, with smaller amounts of water vapour and other gases, and little or no oxygen.
Volcanoes affect the atmosphere by releasing large amounts of some gases, such as carbon dioxide and water vapour, and small amounts of other gases (including nitrogen). There was a lot of volcanic activity on the early Earth, so volcanoes probably helped form its atmosphere.
Earth, Venus and Mars are rocky planets with volcanoes. The atmospheres of Venus and Mars are mainly made of carbon dioxide, thought to have been released by volcanoes. This supports the idea that Earth’s early atmosphere also contained lots of carbon dioxide.
Some scientists think that the Earth’s early atmosphere was mainly nitrogen. Evidence for this comes from Titan, a moon of Saturn. Titan’s atmosphere is 98.4% nitrogen, probably also released by volcanoes. However, space probes have shown that Titan has an icy interior, unlike Earth, Venus or Mars. So, Earth’s early atmosphere is less likely to have been like Titan’s.
SC21b
Describe how the formation of the oceans influenced the composition of the atmosphere.
As the young Earth cooled, water vapour in the atmosphere condensed and formed oceans. Many scientists think that carbon dioxide then dissolved in the oceans, reducing the amount of carbon dioxide in the atmosphere. Sea creatures used the dissolved carbon dioxide to form shells made of calcium carbonate. This then allowed more carbon dioxide to dissolve in the oceans. Carbon dioxide is a very soluble gas. It dissolves readily in water. As the oceans formed, carbon dioxide dissolved and the amount of carbon dioxide in the atmosphere decreased.
SC21b
1) Explain how photosynthetic organisms (including plants) changed the composition of the atmosphere.
2) State the chemical test for oxygen.
1) Some organisms use energy from the Sun to make food by photosynthesis. These organisms change the atmosphere because photosynthesis uses up carbon dioxide and releases oxygen.
2) Oxygen gas will relight a glowing splint.
