Topic 9- Chemistry of the atmosphere

Question 1

What are the current proportions of different gases in the atmosphere?

Answer 1

• about four-fifths (approximately 80%) NITROGEN
• about one-fifth (approximately 20%) OXYGEN
• small proportions of various other gases, including carbon dioxide, water vapour and noble gases.

Question 2

For how long has the atmosphere contained these proportions of gases?

Answer 2

For 200 million years, the proportions of different gases in the atmosphere have been much the same as they are today.

Question 3

Theories about Erath’s atmosphere and how it developed have always changed. Why is this?

Answer 3

Because it is hard to gather evidence over the course of 4.6 billion years - it was a long time period AND happened a long time ago

Question 4

How many phases are there in the evolution of the atmosphere and how can they be summarised?

Answer 4

THREE PHASES
Phase 1 - Volcanoes gave out gases
Phase 2 - Oceans, Algae and Green plants absorbed CO2
Phase 3 - Green plants and algae produced oxygen

Question 5

Phase one took around 1 billion years. What happened in this period?

Answer 5

For the first billion years, the Earth’s surface was covered in volcanoes. When they erupted they released many gases that form the Earth’s early atmosphere

Question 6

What gases composed the atmosphere in phase 1 (the volcanic phase)?

Answer 6

• MAINLY CO2 (95%) with LITTLE/NO O2 - like venus/mars
• Volcanic activity also released NITROGEN, WATER VAPOUR, small amounts of METHANE, and AMMONIA
• Nitrogen gradually built up in the atmosphere
• The water vapour condensed to form oceans

Question 7

In phase 2, the levels of C02 in the atmosphere reduced in 5 ways. Summarise.

*CO2 eventually turns into sediment, rock, and fossil fuels

Answer 7

1) C02 dissolves in the OCEANS
2) This dissolved C02 then forms CARBONATE PRECIPITATES that form SEDIMENT on the sea bed
3) GREEN PLANTS and ALGAE absorbed some C02 so they could photosynthesize
4) Later MARINE ANIMALS evolved and their SHELLS and SKELETONS contained CARBONATES from the ocean. Ocean organisms used C02 to make their CaC03 shells
5) When these organisms died, the carbon they took up from the atmosphere and oceans was locked into ROCKS AND FOSSIL FUELS

Question 8

What are fossil fuels?

Answer 8

Fossil fuels include coal, crude oil, and natural gas

Question 9

The development of fossil fuels in nature reduce the levels of CO2 in the atmosphere, describe in detail how this happens?

Answer 9

• plants, plankton, marine life dies and falls to the seabed
• the remains are BURIED in layers of sediment
• over millions of years, they become compressed and form sedimentary rocks, oil, and gas
• oil, rocks, and gas all trap carbon within them, therefore, reducing co2 levels in the atmosphere

Question 10

What exactly is crude oil, gas, coal, limestone made of?

Answer 10

• crude oil and natural gas are made from plankton. These fossil fuels form RESERVOIRS under the seabed when they are trapped in rocks
• coal is a sedimentary rock formed from thick PLANT DEPOSITS (trees/ferns)
• limestone is also a sedimentary rock. It is made from CALCIUM CARBONATE deposits from SHELLS and SKELETONS of marine organisms

Question 11

In phase 3, green plants and algae produced oxygen, how did this happen?

Answer 11

Green plants and algae produced oxygen during photosynthesis

• 6C02 + 6H20 —— C6H12O6 + 602
• this is how plants use C02 and water via light energy to make sugar/biomass/cellulsoe/starch

Question 12

How do complex life forms now exist on earth?

Answer 12

• algae first evolved 2.7 billion years ago
• 1.7 billion years ago green plants evolved
• as o2 builds up in the atmosphere because of increased photosynthesis, complex life, like animals, can evolve
• 200 million years ago the atmosphere reached the composition its at today - 80% N, 20% 02, 1% OTHER

Question 13

Summary: Describe the mane changes to the atmospher over time?

Answer 13

1) Volcanoes relesed many gases at the start of the Earth’s history
2) CO2 reduced - LOCKED UP
3) 02 increased - PHOTOSYNTHESIS

Question 14

Practice Question: Describe how sedimentary rocks are formed?

Answer 14

1) Volcanoes release CO2
2) CO2 absobed by ocean
3) Marine animals used C02 from the sea to make calcium carbonate shells and skeletons
4) Marine life dies, falls to seabed, buried in layers of sediment
5) Calcium carbonate from the marine life (their shells and skeletons) is compressed to make sedimentary ock like limestone
* AND coal is also a sedimentary rock formed from decomposed and compressed plants that absorbed CO2 from the atmsohere for photosynthesis

Question 15

What are greenhouse gases?

Answer 15

• GHGs act like an insulating layer in the Earth’s atmosphere. GHGs trap heat energy.
• Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life

Question 16

What are the main GHGs?

Answer 16

Carbon dioxide
Methane
and Water vapour

Question 17

Describe the Greenhouse effect in terms of the interaction between short and long wavelength radiation with matter.

• GHGs do not absorb UV radiation

Answer 17

• All particles absorb certain frequencies of radiation
• The sun gives out ELECTROMAGNETIC radiation
• It gives out ULTRAVIOLET (short wl, high energy)
• It also gives out INFRARED (longer wl, low energy)
• Electromagnetic radiation reaches the Earth
• This heats the surface and provides warmth
• In order to cool, the Earth also releases long wave infrared energy into the atmosphere - this is thermal radiation
• GHGs absorb this radiation so it doesn’t fully escape
• GHGs re-radiate this energy back towards the Earth in all directions
• The thermal infrared energy is retained by the atmosphere and causes GLOBAL WARMING/ Greenhouse effect

Question 18

Some human activities increase the amounts of greenhouse gases in
the atmosphere. How is C02 increased?

Answer 18

Burning fossil fuel - carbon that was locked up in these fuels is released as co2. As population increases so does its demand for energy

Deforestation - Fewer trees means less photosynthesis meaning that less CO2 is removed from the atmosphere

Question 19

How are methane levels increased?

Answer 19

INCREASED FARMING/ AGRICULTURE - Farm animals produce methane through their digestive processes. Manure also releases methane

LANDFILL SITES - waste in these sites also releases methane during its decomposition

Question 20

Although GHGs can lead to Global warming, why are they still necessary in the atmosphere?

Answer 20

• Without C02 the Earth’s temperature would be -19 degrees celsius
• All water would be ice and life would not have had a chance to evolve
• GHGs only cause problems when there concentrations in the atmosphere are too high and global temperatures rise

Question 21

What is peer review?

Answer 21

• Before scientists publish their findings in journals and scientific papers, their work is distributed amongst specialists in that field
• This ensures that the work is scientifically VALID and not fabricated

Question 22

Why are speculation, opinions, and BIAS presented in the media that may be based on only parts of
the evidence about climate change?

Answer 22

• Although the Earth’s temperature naturally varies, recently the average temperature of the Earth is increasing
• Most scientists agree that extra C02 released due to human activity is causing this temperature increase
• Although the evidence for this is peer reviewed and therefore reliable, its complexity means that it is difficult to understand
• There are also many variables
• Because of this it is hard to make a model that is not oversimplified
• This has led to speculation in the media where stories may be biased or only present some of the information
• Unfortunately, this speculation can be accepted as fact by the public

Question 23

Students should be able to…..

Answer 23

• evaluate the quality of evidence in a report about global climate change given appropriate information
• describe uncertainties in the evidence base
• recognise the importance of peer review of results and of
  communicating results to a wide range of audiences.

Question 24

An increase in average global temperature is a major cause of climate change.

• describe FOUR potential effects of global climate change
• discuss the SCALE, RISK, and ENVIRONMENTAL IMPLICATIONS of global climate change.

Answer 24

1) Rise in sea levels - A rise in temp causes polar ice caps and glaciers to melt - leads to an increased volume of water in the ocean causing the rise in sea levels.
This leads to INCREASED FLOODING and COASTAL EROSION

2) Storms - their FREQUENCY and SEVERITY may increase
3) Changes in rainfall patterns (amount timing and distribution). Too much or too little can affect crop growth . Both droughts and sever monsoons can cause disruptions - potentially leading to crop failure and famine

4) Changes in the distribution of wildlife species.
- as seasons become less predictable, plants and animals whose FLOWERING/HIBERNATION/REPRODUCTION relies on seasonal factors such as TEMPERATURE/MOISTURE LEVELS may become disrupted along with their HABITATS
- E.g. Animals amy come out of hibernation earlier to find that their normal prey hasn’t appeared
E.g. As temperature rises, polar bears will have fewer ice floes to hunt from
E.g. As temperature and moisture levels increase, species of mosquitoes that carry malaria can thrive in areas further north causing spread of the disease

Question 25

What is ‘carbon footprint’?

Answer 25

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.

Question 26

Why is the carbon footprint difficult to measure?

E.g. Toastie maker

Answer 26

1) Because there are many different factors to consider
- source of all components
- the emissions produced when constructing it
- emissions produced when using it
- emissions released when disposing of it

2) However, a rough calculation can give an idea of the worst emitters so people can avoid them in the future

Question 27

The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane. How is this possible?

Answer 27

1) Increasing the use of ALTERNATIVE/RENEWABLE ENERGY resources

2) Increasing EFFICIENCY of energy use - more efficient processes conserve energy and cut waste
- lots of waste decomposes to give methane emissions so reducing waste will reduce methane
- more efficient engines release fewer GHG emissions
- increasing insulation and using low energy bulbs means less fossil fuels and therefore less emissions are released

3) Using more CARBON CAPTURE STORAGE systems at power plants can also reduce the carbon footprint
- this technology captures carbon dioxide produced from burning fossil fuels before it is released into the atmosphere
- it is stored deep underground in cracks in the rock
- Up to 90% of CO2 emissions from a power plant can be removed in this way

4) Governments could also TAX individuals and companies based on the amount of green house gases they emit
- taxing cars with high emissions would encourage the public to use cars that are more environmentally friendly

5) CARBON OFF-SETTING = actions put in place to reduce the levels of GHGs to compensate for the release of a GHG elsewhere
6) Using CARBON NEUTRAL FUELS

Question 28

MODEL ANSWER: Describe why carbon neutral fuels can reduce GHG emissions and reduce the carbon footprint?

Answer 28

1) Some trees are cut down and used as fuel
2) This is a carbon neutral method because when trees grow they absorb C02 from the atmosphere
3) When they are burned no new CO2 is produced
4) The trees can be planted make it renewable
5) And therefore forms part of the carbon cycle
6) In a similar way, ETHANOL is made from the fermentation of crops that whilst growing, absorb C02 - when the ethanol is COMBUSTED in a car engine, the C02 released is equal to that absorbed during growth making it CARBON NEUTRAL

Question 29

What are the obstacles in reducing carbon footprints?

Answer 29

1) Efforts to reduce carbon emissions are difficult to implement because NOT ALL SCIENTISTS AGREE that GHGs are the cause of climate change.
2) Methods of C02 reduction (CCS) are EXPENSIVE. Construction and the use of power to compress and pump CO2 in the ground would be funded by the public via electricity bills which would nit be popular
3) Increases in use of phones/tablets has led to an INCREASED DEMAND/ LIFESTYLE of electricity. Few people are willing to give up these commodities and some believe they can not live and work in the modern world without them. Education and awareness may help with this

4) Not all countries are interested in lowering Emissions
- many countries abide by the Kyoto Protocol and make efforts to reduce
- Developing countries such as China and India are expempt
- the USA, the largest producer of GHGs, does not want to be involved in the Kyoto Agreement
- GOVERNMENTS DO NOT WANT TO SACRIFICE ECONOMIC GROWTH - important for less developed countries
- Countries do not want To reduce their emissions at a cost if they fear that other countries won’t cooperate

Question 30

Practice Question: Suggest 2 things governments can do to try to reduce GHG emissions of businesses?

Answer 30

1) They could TAX companies based on the amounts of GHGs they emit
2) They could also put a CAP on emissions of all GHGs that companies make — they could then sell licenses for emissions up to that cap

Question 31

Increased C02 is causing climate change but what other ATMOSPHERIC POLLUTANTS are released when fossil fuels are combusted?

Answer 31

Oxides of nitrogen

Sulphur Dioxide

Carbon Monoxide

Soot = carbon products = particulate

Water vapour and CO2 are also released

Question 32

Fossil fuels contain hydrocarbons that are oxidised upon combustion. What is the difference between complete and incomplete combustion?

Answer 32

Complete combustion - This happens when OXYGEN = PLENTIFUL, allowing all the fuel to burn
- C02 is a product of complete combustion

Incomplete Combustion - When there isn’t enough oxygen, all of the fuel does not burn
- under these condition particulates ( Solid particles) of SOOT and UNBURNT FUEL as well as CO2 and CO

E.g. If an engine is old/ poorly maintained, oxygen is less able to reach each alkane molecule in time to convert all of the C to CO2. Instead CO and C are made in the process of incomplete combustion

Question 33

What are the problems associated with particulates being found in the air?

*The main particulate for the purpose of this booklet is soot.

Answer 33

1) If INHALED, they can get stuck in the lungs and cause RESPIRATORY problems
2) GLOBAL DIMMING - if they are in the air, the clouds they produce, reflect sunlight away from the Earth

Question 34

What are the issues with the atmospheric pollutant CARBON MONOXIDE, CO?

Answer 34

= TOXIC

= COLOURLESS + ODOURLESS therefore difficult to detect and makes it even more dangerous

Question 35

How is CO toxic?

Answer 35

1) Binds to Haemoglobin (Hb) that normally carries oxygen - therefore less oxygen is transported around the body
2) A lack of 02 can lead to fainting, coma, and eventually death

Question 36

What are the issues with the atmospheric pollutant C, Soot?

Answer 36

1) Harmful by inhalation
2) May be CARCINOGENIC
3) Can cause GLOBAL DIMMING

Question 37

What are the issues with the unburnt hydrocarbons/alkanes?

Answer 37

These escape from the engine before combustion and are left as RAINBOW RESIDUE on the road from the exhaust pipe

They can VAPORISE to form PHOTOCHEMICAL SMOG that is harmful to health

Question 38

What are the issues with the atmospheric pollutant OXIDES OF NITROGEN (NO, NO2, N204….)?

Answer 38

= harmful to the respiratory system

They are produced from reaction between N2 and 02 in the presence of a spark in the air with high temperatures

This can happen in the INTERNAL COMBUSTION ENGNE of cars

Also contribute to forming ACID RAIN

Question 39

What are the issues with the atmospheric pollutant Sulphur dioxide?

Answer 39

Fossil fuels (crude oil/ coal) are always contaminated with sulphur from the Earth

It is even present after fractional distillation, cracking

= harmful to the respiratory system

Also contribute to forming ACID RAIN

Question 40

What is acid rain?

Answer 40

When SULPHUR DIOXIDE and NITROGEN OXIDES mix with clouds they form DILUTE SULFURIC/NITRIC ACID

This then falls as ACID RAIN

• kills plants
• damages buildings and statues
• corrodes metals

Question 41

Practice Question: Name 3 potential pollutants that can be released as a result of incomplete combustion that would not be released in complete combustion?

Answer 41

Soot/ C/ Particulates

Unburnt Hydrocarbons

CO

Question 42

Tips…

Answer 42

Look at last two pages of section 9 booklet - especially the SUMMARY TABLE

Also look at the equations in these pages