air quality

Question 1

what is the evolution of the atmosphere?

Answer 1

1) created by volcanic activity, cont. water vapour and carbon dioxide
2) cooled, oceans formed from water vapour
3) photosynthetic organisms evolved to use photosynthesis, which removed carbon dioxide and released oxygen, allowing organisms to evolve
4) carbon dioxide was removed by plants + animals dying and becoming buried
5) buried material became fossil fuels
6) carbon dioxide dissolved in oceans to from sedimentary rocks

Question 2

what is the atmosphere and what does it contain?

Answer 2

atmosphere - mixture of gases

contains: 
78% nitrogen
21% oxygen
1% argon 
\+ small amounts of water vapour and carbon dioxide

Question 3

how has human activity changed air quality?

Answer 3

burning fuels in power stations, transport + factories

pollutants - chem harmful to health and environment

carbon dioxide - e - traps heat in atmosphere
nitrogen oxide - e and h - acid rain, asthma worse
sulfur dioxide - e - acid rain
particulates - e and h - buildings dutty , asthma worse
carbon monoxide - h - prevents blood from carrying o2

Question 4

how can air pollution from vehicles be reduced?

Answer 4

• using cars less
• using cleaner fuels
• public transport
• catalytic converters
• low sulfur fuels
• legal limits for exhaust emissions enforced by MOT tests

Question 5

what is complete combustion?

Answer 5

enough oxygen present for fuel to burn

methane + oxygen —–> carbon dioxide + water

Question 6

what is incomplete combustion?

Answer 6

not enough oxygen present for fuel to burn, carbon may be produced

methane + oxygen —–> carbon + water

Question 7

what are hydrocarbons?

Answer 7

petrol, diesel and fuel oil

• contain hydrogen and carbon atoms

Question 8

what happens when a fuel burns?

Answer 8

when hydrocarbon burns:
hydrocarbon fuel + oxygen —–> carbon dioxide + water

oxidation - oxygen added
reduction - oxygen removed
combustion - oxidation reaction

Question 9

burning sulfur?

Answer 9

sulfur + oxygen —–> sulfur dioxide

Question 10

how can power station emissions be reduced by?

Answer 10

• less electricity
• renewable sources eg solar, wind energy
• removing sulfer from gas, coal and oil before burning
• sulfur dioxide removed from waste gases by flue gas desulfurisation
• removing sulfur dioxide from flue by wet scrubbing with spray of calcium oxide and water or seawater

Question 11

what are the effects of pollutants?

Answer 11

environmental problems

particulate carbon - buildings dirty
carbon dioxide - global warming
sulfur and nitrogen dioxide - acid rain, damages trees upsets pH balance of rivers —> aquatic organisms die

Question 12

how is carbon dioxide removed?

Answer 12

by natural processes:

• needed by plants for photosynthesis
• dissolves in rain where it reacts with other chemicals

Question 13

how is nox formed?

Answer 13

nm In furnaces
when nm released it cools and reacts with o2 2 form nd
nm and nd in air so nox represents damages buildings