chemistry - fuels & earth science: earth & atmospheric science (8.18 - 8.26)

8.18 what formed earth’s early atmosphere?

gases produced by volcanic activity

8.19 what was earth’s early atmosphere thought to contain?

little/no oxygen

large amount of CO₂

water vapour

small amounts of other gases

8.19 interpreting evidence about earth’s early atmosphere - Venus & Mars

Earth, Venus, Mars - rocky planets with volcanoes

Venus & Mars - atmospheres mainly CO₂ thought to be released by volcanoes

supports idea earth’s early atmosphere contained lots of CO₂

8.19 interpreting evidence about earth’s early atmosphere - iron pyrite

broken down by oxygen - only forms if no oxygen

found in very ancient rock

suggests little oxygen in earth’s early atmosphere

8.20 oceans formed

earth cooled down

water vapour in atmosphere condensed → liquid water

formed oceans

8.21 how did amount of CO₂ in atmosphere decrease?

oceans formed - CO₂ dissolved in oceans

sea creatures used dissolved CO₂ to form shells made of calcium carbonate - let more CO₂ dissolve in oceans

8.22 growth of primitive plants effect on CO₂ & oxygen

photosynthesis: used CO₂, released oxygen

amount of oxygen in atmosphere gradually increased

8.23 chemical test for oxygen

place glowing splint in oxygen gas

relights

8.24 greenhouse effect

energy transferred from sun → earth - some absorbed by earth’s surface

warm earth emits energy (infrared waves)

gases in atmosphere (CO₂, methane, water vapour) absorb heat from earth

gases release energy - warm’s earth

8.25 evidence for human activity causing climate change - correlation between change in atmospheric CO₂ concentration, consumption of fossil fuels & temp. change

since 1850: burning of fossil fuels steadily increased, CO₂ levels increased

combustion releases CO₂ - fossil fuel use made CO₂ levels increase

CO₂ levels increased - average temp. of earth’s surface increased

strong correlation between CO₂ levels & surface temp.

CO₂ levels increased - infrared waves from earth leaving atmosphere decreased

CO₂ causes temp. rises

8.25 evidence for human activity causing climate change - uncertainties caused by location where measurements taken & historical accuracy

location where measurements taken: only from one place - can’t be used to assess global temp. changes

historical accuracy: earlier measurements less accurate - modern thermometers less prone to error & greater resolution

8.26 composition of today’s atmosphere

78% nitrogen

21% oxygen

0.9% argon

<0.1% CO₂, water vapour, etc.

8.26 potential effects on climate of increased CO₂ & methane levels generated by human activity

CO₂: produced by burning fossil fuels; absorbs infrared radiation from earth - contributes to global warming; dissolves in sea water → lowers pH → harms organisms living in seas & oceans

methane: produced by livestock farming; absorbs infrared radiation from earth (better than CO₂) - contributes to global warming

rising average global temperatures:

• make ice at South Pole & glaciers melt → loss of sea ice at poles, extra water raises sea levels → increasing flooding

• some animals move from natural habitats to find cooler areas

• some animals & plants extinct if can’t survive at warmer temps./find new places to live

• weather patterns change → more extreme weather events → affect wildlife & growth of crops

• makes coral push out photosynthetic algae that live in tissues & provide colour of coral → coral ‘bleaching’ occurs

8.26 mitigating potential effects on climate - methods

use renewable energy resources - reduce greenhouse emissions

reflect sunlight back into space

capture CO₂ from air & bury underground

help locals adapt to new conditions - build flood defences, dams, irrigation systems

8.26 mitigating potential effects on climate - scale

all countries need to work together to reduce emissions & help pay for large-scale engineering

8.26 mitigating potential effects on climate - risks

some countries may not help

could disrupt delicate ecosystems

could destroy important habitats

methods may not work