C9 Flashcards
For 200 million years, proportions of gases in the atomosphere have been the same as today, state the percentage of each gas in the atmosphere
• about four-fifths (approximately 80%) nitrogen
• about one-fifth (approximately 20%) oxygen
• small proportions of various other gases, including carbon dioxide, water vapour and noble gases.
What has happened with theories of what Earth was like in the early atmosphere and why?
Theories about what was in the Earth’s early atmosphere and how the atmosphere was formed have changed and developed over time. Evidence for the early atmosphere is limited because of the time scale of 4.6 billion years.
What does one theory suggest about the first billion years of the Earth’s existence?
One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans. At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.
Volcanoes also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia.
When the oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere. No knowledge of other theories is required.
Note:
AQA says that students should be able to, given appropriate information, interpret evidence and evaluate different theories about the Earth’s early atmosphere.
How did oxygen get into the atmosphere?
Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis
What is the symbol equation for algae and plants producing oxygen?
6CO2 + 6H2O ——> C6H12O6 + 6O2
What is the word equation for algae and plants producing oxygen?
Light
carbon dioxide + water ———-> glucose + oxygen
When did algae first produce oxygen and what happened after?
Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.
What did algae and plants decrease the percentage of?
Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis.
What was another way carbon dioxide was reduced?
Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.
What are the main changes in the atmosphere over time and some of the likely causes of these changes?
Intense volcanic activity – water vapour, carbon dioxide, nitrogen, ammonia, methane released. Water vapour condensed to form oceans. Atmosphere mostly carbon dioxide; nitrogen slowly building up over time.
Describe and explain the formation of deposits of limestone, coal, crude oil and natural gas.
When the plants, plankton and animals died, they fell to the bottom of the seabed and got buried by layers of sediment (mud). Over millions of years, heat and pressure turned the dead material into fossil fuels (coal, crude oil and natural gas) or limestone.
What do greenhouse gases in the atmosphere maintain and state examples of greenhouse gases
Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life.
Water vapour, carbon dioxide and methane are greenhouse gases.
Describe the greenhouse effect in terms of the interaction of short and long wavelength radiation with matter
Electromagnetic radiation from the Sun passes through the Earth’s atmosphere.
The Earth absorbs electromagnetic radiation with short wavelengths.
Heat is radiated from the Earth as longer wavelength infrared radiation.
Some of this infrared radiation is absorbed by greenhouse gases in the atmosphere.
The atmosphere warms up
Some human activities increase the amounts of greenhouse gases in the atmosphere. What do they include?
• carbon dioxide
• methane.
Statw two human activities that increase the amounts of each of the greenhouse gases carbon dioxide and methane
burning fossil fuels in industry, vehicles and power stations releases carbon dioxide.
farming cattle and growing rice in paddy fields releases methane.
Based on peer-reviewed evidence, what do scientists believe that human activities will cause the temperature?
It will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global climate change.
What is a drawback to global climate change?
However, it is difficult to model such complex systems as global climate change. This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased.
Note:
AQA says that students should be able to:
• evaluate the quality of evidence in a report about global climate change given appropriate information
• describe uncertainties in the evidence base
• recognise the importance of peer review of results and of communicating results to a wide range of audiences.
What is a major cause of climate change?
An increase in average global temperature
Describe briefly four potential effects of global climate change
Glaciers and polar ice melting. sea levels rising. patterns of rainfall changing, producing floods or droughts. habitats changing
Discuss the scale, risk and environmental implications of global climate change
extreme weather events. severe impacts on the world’s poorest and most vulnerable populations. environmental and economic damage. large-scale singular events (such as further sea level rise as major ice sheets melt over Greenland and Antarctica)
What is the carbon footprint?
The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
How can the carbon footprint be reduced?
The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane.
