sc21, earth and atmospheric science (paper 2)

Question 1

what formes the earth’s early atmosphere

Answer 1

gases produces by volcanic atmosphere

Question 2

describe today’s atmosphere in terms of percentages

Answer 2

• 78% nitrogen
• 21% oxygen
• 1% other gases (argon, water vapour, carbon dioxide)

Question 3

what did scientists believe the earths early atmosphere contained

Answer 3

• little/no oxygen
• lots of carbon dioxide
• water vapour
• small amounts of other gases

Question 4

what is evidence for scientists beliefs about the early atmosphere

Answer 4

• mixture of gases released by volcanoes
• the atmosphere of other planets in our solar system today (which have not been changed by living organisms)

Question 5

how did the earths atmosphere go from very hot to oxygen building up

Answer 5

• as it cooles, water vapour condensed and fell as rain to form oceans
• forms of life evolve in the oceans
• photosynthesis begins
• oxygen builds up in oceans, and in the atmosphere

Question 6

how did sedimentary rocks form

Answer 6

• carbon dioxide dissolved in the oceans
• marine organisms used this to make calcium carbonate for shells
• the shells of dead marine organisms fall to the sea bed and become part of sediment
• over millions of years, the layers of sediment become squashed and form sedimentary rocks

Question 7

very old rocks don’t have iron oxides, whereas newer rocks do, why?

Answer 7

earlier rocks didn’t have oxygen from the atmosphere

Question 8

how do you test for oxygen

Answer 8

a glowing wooden splint relights in oxygen

Question 9

what happens in the greenhouse effect

Answer 9

• greenhouse gases in the atmosphere absorb heat radiated from the earth
• the greenhouse gases release energy in all directions
• this reduces the amount of heat radiated into space, keeping the earth warm

Question 10

list the gases good at absorbing and emitting energy than others

Answer 10

• carbon dioxide
• methane
• water vapour

Question 11

what is the typical source of carbon dioxide

Answer 11

burning fossil fuels

Question 12

what is the typical source of methane

Answer 12

livestock farming (e.g cattle)

Question 13

what is the typical source of water vapour

Answer 13

evaporation from oceans

Question 14

in which situation is wate vapour not a problem as greenhouse gas

Answer 14

as excess water vapour leaves the atmosphere as rain and snow

Question 15

what is global warming associated with

Answer 15

• long term changes to weather patterns (climate change)
• rising sea levels due to melting ice and expanding ocean water