4.9- Chemistry of our atmosphere Flashcards
What is the proportions of gases in our atmosphere today?
78% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide and trace amounts of other gases.
What did the early atmosphere predominantly contain?
The previous atmosphere predominantly contained carbon dioxide.
Explain the theory on volcanoes.
One theory suggests that the atmosphere was made up through early volcanic eruptions, so carbon dioxide (CO2), water vapour (H2O) and nitrogen made up the early atmosphere.
Explain the theory on water vapour.
Water vapour in the atmosphere condensed as the Earth gradually cooled down, falling as rain, which was collected in hollows in the crust as the rock solidified, forming the first oceans.
Explain the comet theory.
Another theory suggests that icy comets could have also brought water, as when they rained down on the surface of the Earth, they melted, adding to its water supply.
How was the early atmosphere structured?
The early atmosphere was mainly carbon dioxide, water vapour, nitrogen, and traces of methane (CH4) and ammonia (NH3)
Explain why the proportion of oxygen in our atmosphere increased.
The proportion of oxygen increased because of photosynthesis by plants.
Explain why the proportion of ammonia in our atmosphere decreased.
The proportion of ammonia decreased as it reacted with the newly formed oxygen to make nitrogen and water vapour.
Explain why the amount of methane in our atmosphere decreased.
Methane decreased as it reacted with oxygen to form carbon dioxide and water.
Explain why the proportion of carbon dioxide in our atmosphere decreased.
Carbon dioxide decreased because it was locked up in sedimentary rocks, formed from marine animal shells (limestone and chalk) and in fossil fuels. It was absorbed by plants for photosynthesis and it dissolved in oceans.
Explain why nitrogen kept building up in our atmosphere.
It is very unreactive.
What are the main greenhouse gases?
Main greenhouse gases: Carbon dioxide, Methane and Water vapour.
Explain the greenhouse effect.
Short wavelength radiation (ultraviolet radiation) is emitted from the sun
When it strikes the earth’s surface, some of it is absorbed and some is re-emitted from the surface of the Earth as long wavelength radiation (infrared radiation)
Much of the radiation is trapped inside the Earth’s atmosphere by greenhouse gases which can absorb and store the energy
Increasing levels of carbon dioxide and methane, although present in only small amounts, are causing significant upset to the Earth’s natural conditions by trapping extra heat energy
Give some human activities that are contributing to an increase in carbon dioxide in our atmosphere.
Deforestation
Increased burning of fossil fuels
Give some human activities that are contributing to an increase in methane in our atmosphere.
More animal farming
Decomposition of rubbish in landfill sites
What do scientists believe could happen to our atmosphere?
Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global climate change. Some scientists predict that global warming will lead to the Earth’s average temperature increasing by 5.1 degrees celsius by 2100.
What are some potential effects of 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 the food-producing capacity of some regions
- changes to the distribution of wildlife species
What is 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 we reduce the carbon footprint?
increased use of alternative energy supplies
energy conservation
carbon capture and storage (where CO2 is trapped in solvents and stored underground)
Pumping carbon dioxide produced from burning fossil fuels deep underground to be absorbed by porous rocks.
carbon taxes and licences
carbon off-setting including through tree planting
carbon neutrality – zero net release
How can the government help to reduce carbon footprint?
Government measures:
Taxes on emissions
Support the use of renewable energy + electricity
Support use of biofuels
Produce emissions but plants use up carbon dioxide
What are some problems with reducing the carbon footprint?
Problems of reducing the carbon footprint include:
scientific disagreement over causes and consequences of global climate change
lack of public information and education
lifestyle changes (people don’t want to give up their cars)
economic considerations (it will cost money)
incomplete international co-operation
What are some dangerous gases that can be released into the atmosphere when fuels are burnt?
The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide and sulfur dioxide and oxides of nitrogen. Solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere.
What are the advantages of complete combustion?
less soot is made with complete combustion
more heat per gram of fuel is released with complete combustion
poisonous carbon monoxide is not produced with complete combustion
Why is carbon monoxide dangerous?
Carbon monoxide is a toxic gas. It is colourless and odourless and so is not easily detected. Carbon monoxide combines with haemoglobin in the blood reducing its capacity to carry oxygen.
