Chemistry of the Atmosphere

Question 1

What is the theory of the Earth’s early atmosphere?

Answer 1

• In the first billion years, the Earth’s surface was covered in volcanoes which erupted and released lots of gases
• The Earth’s early atmosphere was made up of carbon dioxide, nitrogen and water vapour with small amounts of ammonia and methane

Question 2

What happened to Earth’s early atmosphere once the temperature fell?

Answer 2

• The water vapour condensed forming oceans
• Lots of carbon dioxide was dissolved in the oceans removing it from the atmosphere
• This dissolved carbon dioxide went through a series of reactions to form carbonate precipitates which formed sediments on the seabed
• Green plants and algae evolved and absorbed some of the carbon dioxide to carry out photosynthesis
• Later marine animals evolved and their shells and skeletons contained carbonates from the oceans (some of the carbon the organisms took was from the atmosphere)
• After they died, oceans became locked up in rocks and fossil fuels

Question 3

What happens after, plankton, plants and marine animals die?

Answer 3

• When plankton, plants and marine animals die, they fall to the seabed and get buried by layers of sediments
• Over millions of years they become compressed and form sedimentary rocks, oil and gas (trapping carbon within them and helping to keep carbon dioxide levels in the atmosphere reduced)
• Coal, crude oil and natural gas (fossil fuels) were made by this process

Question 4

How was natural gas and crude oil formed?

Answer 4

• From deposits of plankton
• These fossil fuels form reservoirs under the seabed when they get trapped in rocks

Question 5

How was coal formed?

Answer 5

Coal is a sedimentary rock made from thick plant deposits.

Question 6

What is limestone made of?

Answer 6

Limestone is a sedimentary rock mostly made of calcium carbonate deposits from shells and skeletons.

Question 7

When was the Earth’s early atmosphere?

Answer 7

The Earth’s early atmosphere was 4.6 billion years ago.

Question 7

What happened 2.7 billion years ago?

Answer 7

• Algae evolved 2.7 billion years ago
• Over a billion years later green plants evolved as well
• Algae and plants produced oxygen by photosynthesis (which is when plants use light to convert carbon dioxide and water into sugars)
• This allowed more complex life (animals) evolve

Question 7

What is the equation for photosynthesis?

Answer 7

• light
  6CO2 + 6H2O ——> C6H12O6 + 6O2

Question 8

What happened 200 million years ago?

Answer 8

About 200 million years ago, the atmosphere reached a composition similar to what it is today.

Question 9

What are the gases making up the atmosphere now?

Answer 9

• 78% Nitrogen
• 21% Oxygen
• 0.9% Argon
• 0.04% Carbon dioxide
• Trace amounts of other gases (e.g. water vapour, noble gases)

Question 10

What are the main greenhouse gases?

Answer 10

• Carbon dioxide
• Methane
• Water vapour

Question 11

What do greenhouse gases do?
How does this heat the Earth?

Answer 11

• Allows the Earth to be warm enough to support life
• All particles absorb certain frequencies of radiation
• Greenhouse gases don’t absorb incoming short wavelength radiation from the sun
• Greenhouse gases absorb the long wavelength radiation that is reflected back off the Earth
• Greenhouse gases then re-radiate this heat they absorbed in all directions (including back towards the Earth)
• Since longwave radiation is thermal radiation it results in warming the surface of the Earth - this is called the greenhouse effect

Question 12

What forms of human activity affect the amount of greenhouse gases in the atmosphere?

Answer 12

• Deforestation - this means fewer trees are taking in carbon dioxide from the atmosphere via photosynthesis
• Burning fossil fuels - this releases carbon (in the form of carbon dioxide) that was locked up in these fuels
• Agriculture - this means more farm animals (cows) produce methane through digestive processes
• Creating waste - this means more landfill sites and more waste from agriculture creating more carbon dioxide and methane released by decomposition of waste

Question 13

Why has the average temperature of the Earth’s surface increased?
Why do people speculate this idea?

Answer 13

• Most scientists believe extra carbon dioxide from human activity has caused this increase and that this will lead to climate change
• Evidence for this has been peer-reviewed making the information reliable
• People speculate this (especially in the media due to stories being biased or have limited information given) as it’s hard to fully hard to understand the Earth’s climate because it’s so complex and there are many variables - this means it’s hard to make a model that isn’t oversimplified

Question 14

What are the predictions made from climate change?

Answer 14

• An increase in global temperature can lead to polar ice caps melting - this causes a rise in sea levels and increased flooding in coastal areas and coastal erosion
• Changes in rainfall patterns may lead to some regions receiving too much or too little water - this, along with changes in temperature, may affect the ability of certain regions to produce food.
• The frequency and severity of storms may also increase
• Changes in temperature and amount of water available in a habitat may affect wild species - this leads to differences in their distribution

Question 15

Definition of a carbon footprint:

Answer 15

• Carbon footprints are a measure of the amount of carbon dioxide and other greenhouse gases released over the full life cycle of something
  *This can be a service (e.g. a school bus), an event (e.g. the Olympics), a product (e.g. a toastie maker), etc.
• Measuring carbon footprints can be extremely difficult of impossible - this is because of the amount of different factors to consider

Question 16

How can we reduce carbon footprints?

Answer 16

• Using renewable energy sources or nuclear energy instead of fossil fuels
• Using more efficient processes could conserve energy and cut waste
• Governments could tax companies or individuals based on the amount of greenhouse gases they emit
• Governments can also put a cap on emissions of al greenhouse gases that companies make - this means they can sell licences for emissions up to that cap
• There’s technology that captures carbon dioxide produced by burning fossil fuels before it’s released into the atmosphere (it can be stored deep underground in cracks in the rock such as old oil wells)

Question 17

What are the challenges of making reductions in carbon footprint?

Answer 17

• There’s still a lot of work needed to be done on alternative technologies that result in lower carbon dioxide emissions
• A lot governments are worried that changes will impact the economic growth of communities which could be bad for people’s well-being (this is particularly important for countries that are still developing
• Not everyone is on board - this means it’s hard to make international agreements to reduce emissions - most countries don’t want to sacrifice their economic development if they doubt others won’t do the same
• It’s hard to make individuals change their lifestyle if they don’t want to, in addition, there isn’t enough education provided on why the changes are necessary and how to make them

Question 18

What happens during combustion of fossil fuels?

Answer 18

• Combustion of fossil fuels releases gases and particles
• Crude oil and coal contain hydrocarbons that are oxidised in combustion leading to carbon dioxide and water vapour being released into the atmosphere

Question 19

What happens when there isn’t enough oxygen in combustion?

Answer 19

• When there isn’t plenty of oxygen, incomplete combustion happens where some of the fuel doesn’t burn
• Under these conditions, solid particles (called particulates) of soot (carbon) and unburnt fuel are released and produce carbon monoxide as well as carbon dioxide

Question 20

What problems occur when particulates are in the air?

Answer 20

• If the particulates are inhaled it can lead to respiratory problems as it can get stuck in the lungs and cause damage
• Particulates are bad for the environment - they produce clouds that reflect sunlight back to space - this means less light reaches the Earth causing global dimming

Question 21

What problems occur with carbon monoxide?

Answer 21

• Carbon monoxide is dangerous as it can stop your blood carrying oxygen around the body - this happens when carbon monoxide binds to the haemoglobin in your blood
• A lack of oxygen in the blood can lead to fainting, a coma or death
• Carbon monoxide is a toxic gas that is odourless and colourless making it harder to detect

Question 22

What happens when sulfur dioxide and nitrogen oxides are released?

Answer 22

• Sulfur dioxide is released during the combustion of fossil fuels (e.g. coal) that contain sulfur impurities - this sulfur in the fuel becomes oxidised
• Nitrogen oxides are created from a reaction between the nitrogen and oxygen in the air, caused by the heat of the burning (this can happen in the internal combustion engines of cars)
• When these gases mix with clouds, they form dilute sulfuric acid or dilute nitric acid - this then falls as acid rain
• Acid rain kills plants and damages building and statues
• Acid rain makes metals corrode
• Sulfur dioxide and nitrogen oxide are bad for your health and can cause respiratory problems if they are inhaled

Question 23

How to test for sulphur dioxide?

Answer 23

You can test for sulfur impurities through a solution containing universal indicator. If they fuel contains sulfur the universal indicator will become red.