chemistry of the atmosphere Flashcards
name the proportion of gases in the atmosphere of the earth today and how long have these proportions been the same before?
- 78% nitrogen
- 21% oxygen
- small proportions of other gases including carbon dioxide, water vapour, and argon
- these proportions have been the same for 200million years
explain what has led to the changes of the percentages of carbon dioxide and oxygen from the earths early atmosphere to the earths atmosphere today
- carbon dioxide has decreased
- this is because volcanic activity released water vapour which condensed to form oceans
- some carbon dioxide dissolved in oceans
- and some carbon was locked in sedimentary rocks
- oxygen has increased
- this is because algae and plants evolved and they absorbed carbon dioxide for photosynthesis which also released oxygen (meaning there was less carbon dioxide and more oxygen)
why are scientists not certain about the percentage of each gas in the earths early atmosphere?
as the earth is 4.6 billion years old so there is limited or no evidence
how did nitrogen come into the early atmosphere?
volcanos produced nitrogen which gradually built up in the atmosphere
how were deposits of limestone formed?
limestone
- some of the carbon dioxide dissolved in the oceans to form weak acids
- this reacted with minerals in the sea to produce precipitates
- overtime this formed sediments of carbonate rock on the sea bed
- some of the carbon dioxide in the sea was used to make corals and shells of organisms such as mussels
- when these died they formed the sedimentary rock limestone
how were deposits of coal formed?
- coal is formed from the remains of ferns and trees
- if these die in marshy wetlands then they do not decompose which can be due to a lack of oxygen or acidic conditions
- these both prevent bacteria from carrying out decomposition
- over time the plant remains are covered with sediment and compressed
- high temperature and pressure created coal
how were deposits of crude oil formed?
- crude is formed from plankton which die and settle in mud on the seabed
- if oxygen is not present then they do not decompose
- overtime they are compressed by sediment
- heat and pressure then convert them into crude oil
how were deposits of natural gas formed?
- natural gas is mainly the hydrocarbon methane
- we often find natural gas near deposits of oil
- is formed from plankton
- all fossil fuels contain trapped carbon
describe the greenhouse effect
- energy from the sun travels to the earth as short wavelength radiation e.g. ultraviolet and visible light
- some of the short wavelength radiation reflect back into space but most of it passes easily through the atmosphere because short wavelength radiation does not interact strongly with the gas molecules in 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
- because the energy is trapped in the atmosphere, this causes the temperature of the atmosphere to increase
- the greenhouse effect keeps the temperature warm enough to support life
what is the carbon footprint?
the carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full lifecycle of a product, service, or event
how can the carbon footprint be reduced?
by reducing emissions of carbon dioxide and methane
how can we reduce emissions of carbon dioxide?
- a lot of energy is used to heat our homes by burning fossil fuels. by insulating our homes or turning down the heating, we can reduce carbon dioxide emissions
- a lot of carbon dioxide is released by driving cars. we can reduce this by using public transport such as buses or trains. these release less carbon dioxide per passenger.
- a lot of carbon dioxide is produced by generating electricity by burning fossil fuels. we can reduce this by switching to renewable sources of energy such as wind power. we can also reduce how much electricity we use at home by switching to energy saving lightbulbs and turning appliances opp at the plug rather than leaving them on standby
why may the actions of reducing carbon dioxide and methane emissions be limited?
- as most of these solutions are expensive and people are reluctant to pay
- they may be inconvenient for example many people prefer the convenience of driving over public transport
how can we reduce emissions of methane and why might this be limited?
- one of the biggest sources of methane is agriculture. grazing cattle such as cows release methane when they fart. one way to reduce this is for people to eat less beef and les dairy products. the problem is that people enjoy eating these and are unlikely to change their diet
- landfills produce methane. we can reduce this by trapping the methane and burning it to produce electricity. this is a good idea because methane is a much stronger greenhouse gas than carbon dioxide. this may be limited as trapping and burning methane costs money
What is a major source of atmospheric pollutants?
The combustion of fuels
