Chemistry of the atmosphere

Question 1

what happened during the first billion years of Earth

Answer 1

• no plant or animal life
• lots of volcanic activity which released
  * mostly CO2
  * water vapour ( condenses to form seas)
  * small proportions of methane and ammonia
  * nitrogen (gradually built up in the atmosphere)

Question 2

What happened after 2.7 billion years

Answer 2

• water vapour condenses to form seas
• lots of carbon dioxide dissolved in the ocean
• the carbon in carbon dioxide becomes locked up in sedimentary rocks formed from the shells and skeletons of marine organisms
• Green plants and algae evolve

Question 3

what happened when carbon dioxide dissolved in the ocean

Answer 3

• carbon precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere

Question 4

the proportion of gases in the atmosphere have been more or less the same for about 200 million years.
what is the proportion of gases in the atmosphere today?

Answer 4

4/5 nitrogen (78%)
1/5 oxygen (21%)
small proportions of CO2 (0.04%), argon, water vapour and other noble gases

Question 5

what caused an increase in oxygen levels?

Answer 5

• Algae and plant photosynthesise
  (6CO2 + 6H2O = 6O2 +C6H12O6)
• Algae gist started producing oxygen about 2.7 billion years ago
• Over the next billion years, plants evolved and the amount of oxygen increased
• eventually, the level of oxygen in the atmosphere increased enough to allow animals to evolve

Question 6

what happened when green plants and algae evolved?

Answer 6

• CO2 is reduced as the plants take it in and give out oxygen
• microorganisms that can’t tolerate oxygen are killed off
• nitrogen is also produced by bacteria removing nitrates from decaying plant material

Question 7

what caused a decrease in CO2 levels

Answer 7

• photosynthesis
• carbon becomes locked up in sedimentary rocks (e.g limestone) and fossil fuels ( e.g crude oil, coal and natural gases)
• the reaction between carbon dioxide and seawater which produces insoluble carbonates that are deposited as sediment and soluble hydrogen carbonates.

Question 8

how is limestone formed?

Answer 8

Limestone contains calcium carbonate and can be formed from the shells and skeletons of sea creatures

Question 9

How is coal formed?

Answer 9

• a sedimentary rock

- formed from plant deposits that were buried and compressed over millions of years

Question 10

How are crude oil and natural gases produced?

Answer 10

formed from deposits of plankton. these fossil fuels form reservoirs under the sea bed when they get trapped in rocks

Question 11

Explain and describe how the Earth warms up.

Answer 11

1) High energy short-wavelength infrared radiation from the sun passes through the atmosphere and reaches the Earth’s surface. Some of this is absorbed by the Earth
2) Lower energy, long-wavelength infrared radiation is reflected by the Earth’s surface
3) Greenhouse gases in the Earth’s atmosphere absorb the long wavelength radiation that is reflected and re-radiate it in all directions - including back towards the search which increases its temperature.

Question 12

Name some greenhouse gases

Answer 12

CO2

water vapour

methane

Question 13

What are examples of human activities that negatively impact the Earth?

Explain how they negatively impact the Earth

Answer 13

• Deforestation = fewer trees = less CO2 removed from the atmosphere via photosynthesis
• Burning fossil fuels = carbon that was locked up in these fuels is released as CO2
• Decomposition of rubbish in a landfill site and increased animal farming = increase levels of methane

Question 14

How is methane produced?

Answer 14

it is produced by animals during digestion and decomposition of the waste materials

Question 15

Many scientists believe that the increase in the levels of greenhouse gases in the atmosphere causes global warming and climate change.

Why is this information reliable?

Answer 15

because it has been peer-reviewed

Question 16

Why do people use simplified models of climate change?

Answer 16

because the Earth’s climate is complex and there are so many variables

Question 17

What can the impact of climate change include? (7)

Answer 17

• a rise in sea levels: causing devastating floods and more coastal erosion
• more frequent and severe storm events
• changes in the amount and timing of rainfall = areas receiving more rain and others receiving much less
• an increased number of heatwave events,
• more droughts
• changes to the distribution of plants and animals, as some areas warm up enough to become too hot for species to survive
• food shortages in some areas, due to changes in the number of food that countries can produce

Question 18

What is a carbon footprint?

Answer 18

a measure of the amount of CO2 ns other greenhouse gases released over a full cycle of something

(service, an event, a production)

Question 19

How can carbon footprint be reduced?

Answer 19

• renewable energy sources or nuclear energy instead of fossil fuels
• wasting less energy by using a more efficient process
• carbon capture and storage (CCS) to prevent CO2 from being released into the atmosphere
• carbon taxes and licenses, to deter companies and individual from choosing options that release lots of greenhouse gases
• carbon off-setting, through activities such as tree planting
• encouraging people to choose carbon-neutral products

Question 20

What are the problems over reducing carbon footprints?

Answer 20

• disagreements between scientists over the causes and consequences of global climate change
• lack of information and knowledge in the general population
• the reluctance of people to make lifestyle changes
• economic considerations, such as the high cost of producing electricity from alternative energy resources, rather than using cheaper fossil fuels
• disagreements between countries as to what should be done

Question 21

What’s the word formula for the combustion of methane?

Answer 21

methane + oxygen = water + carbon dioxide

Question 22

Describe how oxides of nitrogen are produced when petrol is burned in car engines.

Answer 22

Nitrogen from the atmosphere reacts with oxygen from the atmosphere at high temperatures in the engine

Question 23

What is the main source of atmospheric pollutants

Answer 23

combustion of fuels

Question 24

What do most fuels, including coal, contain?

Answer 24

carbon

and/or hydrogen

may also contain some sulfur.

Question 25

What substances are released when fuels undergo combustion?

7

Answer 25

carbon dioxide 
water vapour, 
carbon monoxide, 
sulfur dioxide 
oxides of nitrogen.

Solid particles and unburned hydrocarbons may also be released that form particulate in the atmosphere.

Question 26

What environmental and human problems do sulfur dioxide and oxide of nitrogen cause?

Answer 26

Acid rain

respiratory problems

Question 27

What problems do carbon particulates cause?

Answer 27

Global dimming and health problems for humans

Question 28

What problems do carbon monoxide cause?

Answer 28

toxic gas = detrimental to health

acid rain

Question 29

What is a catalytic converter?

what does it do, what gases does it change

Answer 29

it converts toxic gases from the exhaust pipe to harmless ones - this is in the exhaust systems

They contain platinum and rhodium, which act as catalysts
it changes carbon monoxide into carbon dioxide.

Changes oxides of nitrogen to nitrogen

Question 30

What enables the catalytic convertors to be good at their job?

Answer 30

A honeycomb structure is coated in platinum and rhodium.

The honeycomb structure increases the surface area to volume ratio, increasing the rate at which the harmful gases carbon monoxide, nitrous oxide and methane are converted into carbon dioxide, nitrogen and water.

since the metals used are catalysts, they lower the activation energy also increases the rate of reaction.