C1g

Question 1

What are the stages of the evolution of the atmosphere?

Answer 1

• volcanoes gave out steam and CO2
• green plants evolved and produced oxygen
• ozone layer allowed evolution of complex animals

Question 2

What happened in phase 1 of the evolution of the atmosphere?

Answer 2

1-Earth surface originally molten, any atmosphere boiled away
2-it cooled and thin crust formed, volcanoes kept erupting, releasing gases from inside the earth. Degassing released mainly CO2, but also steam and ammonia
-atmosphere mostly CO2 and water vapour
-water vapour condensed to form oceans
-very little oxygen

Question 3

What happened in phase 2 of the evolution of the atmosphere?

Answer 3

• lots of CO2 dissolved into oceans
• green plants evolved almost everywhere and photosythesised, removing CO2 and producing O2
• O2 gradually built up and CO2 locked up in fossil fuels and sedimentary rocks
• N2 put in atmosphere by ammonia reacting with oxygen and released form denitryfying bacteria
• N2 is not very reactive so the amount in the atmosphere increased

Question 4

What happened in phase 3 of the evolution of the atmosphere?

Answer 4

• buildup of oxygen killed early organisms that couldn’t tolerate it
• allowing evolution of complex organisms that make use of oxygen
• oxygen created the ozone layer (O3), blocking harmful UV rays and enabling even more complex organisms to evolve
• virtually no CO2 left

Question 5

What does today’s atmosphere contain?

Answer 5

• 78% nitrogen
• 21% oxygen
• 0.035% carbon dioxide
• varying amounts of water vapour
• noble gases (mainly argon)

Question 6

What processes in the carbon cycle remove oxygen and release carbon dioxide?

Answer 6

• respiration
• combustion
• decay

Question 7

What processes in the carbon cycle remove carbon dioxide and release oxygen?

Answer 7

-photosyntehsis

Question 8

How has human activity affected the composition of air?

Answer 8

• more people and developing countries, more energy needed, more fuel burnt, more pollutants released
• more people=more land to grow food and build houses, deforestation to make space, less plants, less photosynthesis, less carbon dioxide taken out of the atmposphere

Question 9

What do catalytic converters do?

Answer 9

• are one motor vehicles to reduce amount of carbon monoxide and nitrogen oxides getting in the atmosphere
• made of mixture of platinum and rhodium

Question 10

What is photochemical smog, how it it caused, and what effects does it have?

Answer 10

• caused by sunlight reacting with nitrogen oxides
• oxides combine with oxygen to produce ozone (O3)
• breathing difficulties, headaches and tiredness

Question 11

How does carbon monoxide get into the atmosphere?

Answer 11

-formed when petrol or diesel in car engines burns without enough oxygen, incomplete combustion

Question 12

How is acid rain caused?

Answer 12

• burning fossil fuels also releases sulfur dioxide and nitrogen oxides
• when the gases mix with the clouds they form dilute sulphuric and nitric acid
• this falls as rain
• main cause:power stations and internal combustion engines

Question 13

What does acid rain cause?

Answer 13

• causes lake to become acidic and may plants and animals die
• kills trees and erodes limestone buildings and stone statues
• makes metal corrode

Question 14

Where does sulfur dioxide come from?

Answer 14

-sulfur impurities in fossil fuels

Question 15

Where does nitrogen oxides come from?

Answer 15

• a reaction between oxygen and nitrogen in air, caused by the heat of burning
• happens in car engines