9.1.3 & 9.1.4 How oxygen increased and how carbon dioxide decreased

Question 1

Photosynthesis equations

Answer 1

carbon dioxide + water = glucose and oxygen

Question 2

How did oxygen increase (2p)

Answer 2

• Algae and plants produced oxygen by photosynthesis
• Over a billion years, plants evolved and the percentage of oxygen gradually grew to a level than allowed animals to evolve

Question 3

How carbon dioxide decreased (3p)

Answer 3

• Photosynthesis
• Absorbed by oceans
• Trapped by the formation of fossil fuels and sedimentary rocks

Question 4

Igneous rock formation

Answer 4

Igneous rocks are formed from the cooling of molten rock

Question 5

Intrusive rock

Answer 5

Intrusive igneous rocks are formed by magma that has cooled slowly, deep underground

Question 6

Extrusive rock

Answer 6

Extrusive igneous rocks are formed by magma that has erupted onto the surface as lava and then cooled quickly

Question 7

Formation of coal (3p)

Answer 7

-formed from trees which were in low-lying wetland areas.
-Flooding caused the wood from these forests to be buried in a way that prevented oxidation taking place.
- Compression and heating over millions of years turned the wood into coal.

Question 8

Formation of crude oil and natural gas (5p)

Answer 8

• Formed from simple plants and animals which were living in oceans
• These small organisms died and their remains sank to the bottom where they were buried under sediments.
• This prevented oxidation from occurring.
• Over millions of years, heat and pressure turned the remains of the organisms into crude oil and natural gas.
• Natural gas contains the smallest molecules and is often found on top of crude oil, trapped under sedimentary rock