chemistry of the atmosphere Flashcards
Give the proportion of oxygen, water vapour, carbon dioxide, nitrogen and noble gases (like argon).
gases in the atmosphere today:
- about 78% is nitrogen
- about 21% is oxygen
- small proportion of carbon dioxide, water vapour and noble gases (like argon) and other gases
How long has the atmosphere been the way it is today?
The way the atmosphere is today has been like this for the past 200 million years.
How old is the earth?
The earth is about 4.6 billion years old. For that reason, it is hard for scientists to be certain about the early atmosphere.
What do scientists believe happened to the atmosphere in the first billion years of the earth’s life?
first billion years of the earth:
- intense volcanic activity, which released gases to form the atmosphere
- one was water vapour, which condensed as the earth cooled to form oceans
- another was lots of carbon dioxide, so in early stages, mainly CO2 and barely any O2, so similar to Mars or Venus today
- another was nitrogen, which gradually built up over time
- small proportions of methane and ammonia produced
What happened when the oceans first formed?
when the oceans first formed:
- some of the CO2 dissolved in the water 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
- this removed some of the CO2 from the atmosphere
- some of the other CO2 in the sea was used to make corals and shells of organisms, like muscles
- when these died, they formed limestone, which removed more CO2 from the atmosphere
Describe how oxygen levels became suitable to allow animals to evolve.
- about 2.7 billion years ago, photosynthetic algae first evolved in the oceans, which produced oxygen and it entered the atmosphere
- over the following billion years, plants evolved, increasing the level of O2 and decreasing the CO2
- at some point, the O2 reached a level where animals could evolve
- also, some of the carbon was trapped in fossil fuels, which decreased the level of CO2
Give the word and symbol equation for photosynthesis.
carbon dioxide + water –> glucose + oxygen
6CO2 + 6H2O –> C6H12O6 + 6O2
Describe the formation of coal.
coal:
- formed from the remains of ferns and trees
- if they die in marshy wetlands, they do not decompose, which is due to a lack of O2 and acidic conditions, which prevents bacteria from carrying out respiration to decompose
- over time, the plant remains are covered in sediment and are compressed and high temperature and pressure creates coal
Describe the formation of oil.
oil:
- crude oil is formed from plankton (tiny plants and animals in the sea)
- when they die, they settle in mud on the sea bed
- if O2 isn’t present, they don’t decompose as it prevents bacteria from carrying out respiration
- over time, they are compressed by sediment and heat and pressure convert them to crude oil
Describe the formation of gas (fossil fuel).
gas:
- natural gas is mainly the hydrocarbon methane
- gas is usually near to deposits of oil as they form in a similar way, just with added heat and pressure
- gas is formed from plankton (tiny plants and animals in the sea)
- when they die, they settle in mud on the sea bed
- if O2 isn’t present, they don’t decompose as it prevents bacteria from carrying out respiration
- over time, they are compressed by sediment and lots of heat and pressure convert them to gas
Name three greenhouse gases and their abundance in the atmosphere.
greenhouse gases:
- water vapour (variable based on temperature)
- carbon dioxide (about 0.04%)
- methane (abour 0.0002%)
Describe the greenhouse effect.
the greenhouse effect:
- energy from the sun travels to the earth by passing through the atmosphere as short wavelength radiation (eg. ultraviolet, visible light)
- some reflects back into space, but most 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 radiates the energy as long wavelength (eg. infrared)
- some energy is absorbed by the greenhouse gas molecules, and because the energy is trapped in the atmosphere
Why is it important to keep the earth at a warm level?
It is important to keep the earth at a warm level to support life on earth, so without it, it would be too cold for most organisms to survive.
Why are carbon dioxide levels increasing?
CO2 levels increasing:
- we burn fossil fuels (eg. coal for electricity, petrol and diesel for cars, gas for heating homes)
- deforestation (less absorption)
- burning forests
Why are methane levels increasing?
methane levels increasing:
- growing rice in flooded paddy fields
- when cattle (cows) pass wind
Give three effects of climate change.
effects of climate change:
- increased melting of polar ice sheets and glaciers, which leads to increased sea levels, which could lead to more flooding in low-lying areas
- more severe weather (eg. more storms in the UK)
- change the distribution of animals (eg. mosquitoes may move to places more suitable for their climate)
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.
Give five ways to reduce the CO2 emissions.
reducing CO2 emissions:
- use insulation in homes
- turn down heating
- use public transport instead of driving
- switch to renewable sources of energy
- reduce how much electricity is used at home (eg. turn off appliances, energy saving lightbulbs)
Give two problems with the solutions to climate change.
problems with solutions to climate change:
- most solutions are expensive and people are reluctant to pay
- in some cases, they are inconvenient
Give two ways to reduce methane emissions.
reducing methane emissions:
- eat less beef and dairy products (however, people enjoy these and are unlikely to change)
- at landfills, trap methane and burn it for electricity (especially good as methane is a more powerful gas, however it is expensive)
What is a fuel?
Fuels release energy when they are combusted (burned). For example, coal to generate electricity in power stations, or hydrocarbons to power vehicles.
What happens when fuels are burned?
Most fuels contain carbon and hydrogen. When we burn them, the carbon and hydrogen atoms are oxidised (react with the oxygen in the air) to form CO2 and H20, which are greenhouse gases.
State the word and symbol equation for the combustion of methane.
methane + oxygen –> carbon dioxide + water
CH4 + 2O2 –> CO2 + 2H20
What is complete combustion?
Complete combustion is when there is plenty of O2, so CO2 is made.
