The atmosphere Flashcards
What are the proportions of gases in the Earth’s atmosphere today?
-About four-fifths (approximately 80%) nitrogen
- about one-fifth (approximately 20%) oxygen
-small proportions of other gases, including carbon dioxide, water vapour, and noble gases.
How long have the proportions of gases in the atmosphere been much the same as today?
- For 200 million years.
Why is evidence of the Earth’s early atmosphere limited?
-Because of the time scale of 4.6 billion years.
What is one theory about the Earth’s early atmosphere?
-During the first billion years, intense volcanic activity released gases that formed the early atmosphere and water vapour that condensed to form oceans. The atmosphere may have been mainly carbon dioxide with little or no oxygen.
How did volcanoes affect the early atmosphere?
- Volcanoes produced nitrogen which gradually built up in the atmosphere, and there may have been small proportions of methane and ammonia.
What happened when the oceans formed in the early Earth?
- Carbon dioxide dissolved in the water, and carbonates were precipitated, reducing the amount of carbon dioxide in the atmosphere.
How did algae and plants contribute to the oxygen in the atmosphere?
Algae and plants produced oxygen through photosynthesis, which can be represented by the equation:
6CO(2) + 6H(2)O + sunlight → C(6)H(12)O(6) + 6O(2).
When did algae first produce oxygen, and when did oxygen appear in the atmosphere?
-Algae first produced oxygen about 2.7 billion years ago, and soon after, oxygen appeared in the atmosphere.
How did oxygen levels increase in the atmosphere?
-Over the next billion years, plants evolved, and the percentage of oxygen gradually increased, enabling animals to evolve.
How did algae and plants decrease the percentage of carbon dioxide in the atmosphere?
-Through photosynthesis.
How else was carbon dioxide reduced in the atmosphere?
- By the formation of sedimentary rocks and fossil fuels that contain carbon.
What are greenhouse gases, and why are they important?
- Greenhouse gases, like water vapour, carbon dioxide, and methane, maintain temperatures on Earth high enough to support life.
How do human activities affect greenhouse gases?
- Human activities increase the amounts of greenhouse gases, including carbon dioxide and methane, in the atmosphere.
What do many scientists believe about human activities and global climate change?
- Many scientists believe human activities will cause the temperature of the Earth’s atmosphere to increase at the surface, leading to global climate change.
Why is it difficult to model global climate change?
- Because global climate change is a complex system, leading to simplified models, speculation, and opinions that may be biased.
What is a major cause of climate change?
- An increase in average global temperature.
What is the carbon footprint?
-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?
-By reducing emissions of carbon dioxide and methane.
What is a major source of atmospheric pollutants?
- The combustion of fuels.
What gases are released when fuels are burned?
-Carbon dioxide, water vapour, carbon monoxide, sulfur dioxide, and oxides of nitrogen. Solid particles and unburned hydrocarbons may also be released as particulates.
Why is carbon monoxide dangerous?
-Carbon monoxide is a toxic gas, colourless and odourless, so it is not easily detected.
What health problems are caused by sulfur dioxide and oxides of nitrogen?
- They cause respiratory problems in humans and contribute to acid rain.
What are the effects of particulates in the atmosphere?
- Particulates cause global dimming and health problems for humans.
what are ways we can reduce carbon emissions ? + cons
-insulating our homes or turning down heating
-using public transport and buses which releases less carbon dioxide per passenger
-using renewable sources of electricity and power
-expensive + inconvenient
how should we reduce methane?
-by eating less beef and less dairy products
-trapping methane and burning it to produce electricity
what were two key differences between the early atmosphere and the atmosphere today?
-the early atmosphere contained large amounts of carbon dioxide but the atmosphere today only contains a small amount
-the early atmosphere contained very little oxygen whereas today 21% of the atmosphere is oxygen
what happened when water vapour from volcanoes condensed to form oceans?
-some of the carbon dioxide dissolved in the ocean to form a weak acid
-this reacted with minerals in the sea to form precipitates
-over time, this formed sediments of carbonate rock on the sea bed
how is coal formed and why do they not decompose when they die? + what is required
-from the remains of ferns and trees and if these die in marshy wetlands they do not decompose
-this can be due do lack of oxygen or acidic conditions - both of which prevent bacteria from carrying out decomposition
-over time, the plant remains are covered with sediment and compressed
-high temperature and pressure creates coal
how is crude oil formed and why do they not decompose?
-from plankton which are sea creatures that die in mud on the sea-bed
-if oxygen is not present they do not decompose
-over time they are compressed by sediment
-heat and pressure convert them into crude oil
how is natural gas formed?
where is natural gas found?
what is natural gas?
-natural gas is mainly the hydrocarbon methane
-we often find natural gas near deposits of oil.
-natural gas is formed from plankton in a similar way to oil.
why do all fossil fuels contain trapped carbon?
-carbon was part of the carbon dioxide taken in by photosynthesis
what causes the temperature of the atmosphere to increase?
-energy from the sun travels to the earth as short wavelength radiation e.g ultraviolet and visible light
-some of the short wavelength radiation reflects back into space but most of it passes early though the atmosphere
-the energy of the radiation is absorbed when it reaches the surface of the earth
-the surface of the earth now radiates the energy as long wavelength radiation such as infra-red
-some of the long wavelength radiation interacts with the greenhouse gas molecules in the atmosphere
-the energy in the long wavelength radiation is absorbed
-due to the energy trapped in the atmosphere, this causes the temperature of the atmosphere to increase
why do some of the short wavelength radiation reflect back into space?
-this is because short wavelength radiation does not interact strongly with gas molecules in the atmosphere
what would happen without the greenhouse effect?
-the earth would be too cold for most living organisms to survive
what are the advantages of complete combustion?
-less soot is made
-more heat per gram of fuel is released
-poisonous carbon monoxide is not produced
what are the potential effects of global climate change?
-sea level rise, which may cause flooding and increased coastal erosion
-more frequent and severe storms
-changes in the amount, timing and distribution of rainfall
-temperature and water stress for humans and wildlife
-changes in food-producing capacity of some regions
-changes to the distribution of wildlife species
