Chemistry of the atmosphere

Question 1

current proportion of gases

Answer 1

around 80% nitrogen
around 20% oxygen
small proportions of other various gases including carbon dioxide, water vapour and noble gases

Question 2

What was the earth’s early atmosphere like

Answer 2

Intense volcanic activity that released gases that formed the early atmosphere, and water vapour condensed to form oceans.
Earth’s atmosphere may have been like the atmospheres of Mars or Venus, consisting of mainly carbon dioxide and little to no Oxygen gas

Question 3

What did volcanoes produce

Answer 3

Volcanoes produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia

Question 4

How carbon dioxide levels decreased

Answer 4

• Algae and plants decreased the percentage of carbon dioxide by photosynthesis
• Carbon dioxide dissolved in the newly formed oceans and were precipitated into sediments
• carbon dioxide decreased by the formation of sedimentary rocks and fossil fuels that contain carbon
• limestone is a sedimentary rock, mainly calcium carbonate formed from the shells and skeletons of marine organisms

Question 5

how nitrogen increased

Answer 5

• volcanoes produce nitrogen
• denitrifying bacteria produced nitrogen
• ammonia reacted with oxygen to produce nitrogen

Question 6

How oxygen increased

Answer 6

• Algae and plants produced oxygen by photosynthesis.
  Carbon dioxide + water -> glucose + oxygen
  Algae first produced oxygen about 2.7 billion years ago

Question 7

what do greenhouse gases do

Answer 7

greenhouse gases in the atmosphere maintain temperatures on earth high enough to support life.
water vapour, methane and carbon dioxide are greenhouse gases

Question 8

Enhanced greenhouse gas effect

Answer 8

• the sun emits shortwave radiation and is absorbed by the earth’s surface, warming it up
• the earth re-emits this radiation as long wave radiation but greenhouse gases absorb and trap the L.W radiation
• earth’s surface warms up even more as L.W radiation is re-emitted

Question 9

causes of an increase in CO2

Answer 9

• combustion of fossil fuels
• deforestation

Question 10

causes of an increase in Methane

Answer 10

• more animal farming - digestion and waste decomposition
• decomposition of rubbish in landfill sites

Question 11

cause of climate change

Answer 11

an increase in average global temperature

Question 12

effects of climate change

Answer 12

• sea levels rise which may cause flooding and coastal erosion
• more frequent and severe storms
• changes in the amount, timing and distribution of rainfall
• temperature and water stress for humans and wildlife
• changes in the food-producing capacity of some regions
• changes to distribution of wildlife species

Question 13

what is a carbon footprint

Answer 13

Total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event

Question 14

Reducing carbon footprint

Answer 14

• Increased use of alternative energy supplies
• energy conservation
• carbon capture (CO2 is trapped in solvents, stored underground)
• carbon taxes and licences
• carbon off-setting including through tree planting
• carbon neutrality - zero net release

Question 15

problems with reducing carbon footprint

Answer 15

• scientific disagreements over the causes and consequences of global climate change
• lack of public information and education
• life style changes (people don’t want to give up their cars)
• economic considerations ( will cost money)
• incomplete international co-operation

Question 16

what do majority of fuels contain

Answer 16

carbon and/or hydrogen and sometimes sulfur

Question 17

complete combustion

Answer 17

plentiful oxygen supply
products are water and carbon dioxide

Question 18

incomplete combustion

Answer 18

insufficient oxygen
products are carbon monoxide and soot
CO is a toxic gas - colourless and odourless so it isn’t easily detected. It binds with haemoglobin in the blood reducing its capacity to carry oxygen

Question 19

advantages of complete combustion

Answer 19

• less soot is made
• more heat per gram of fuel is released
• poisonous CO is not produced

Question 20

problems with sulfur dioxide and oxides of nitrogen

Answer 20

can cause respiratory problems in humans and cause acid rain.
Acid rain damages plants and buildigns

Question 21

how are oxides of nitrogen produced

Answer 21

Reaction of nitrogen and oxygen from the air at high temperatures e.g. a car engine

Question 22

Problem with particulates

Answer 22

Particulates such as carbon particles can cause global dimming, reducing the amount of sunlight that reaches the earth’s surface.
Particulates can cause health problems for humans because of damage to the lungs