Topic 1- The Earth's Sea and Atmosphere

Question 1

how long ago did the Earth form?

Answer 1

4.6 billion years ago

Question 2

what was the composition of the earth’s early atmosphere?

Answer 2

(in order of most to least)

• carbon dioxide
• water vapour
• other gases (ammonia, methane, hydrogen)

Question 3

what is the composition of the earth’s current atmosphere?

Answer 3

(in order of most to least)

• nitrogen ( 78% )
• oxygen ( 21% )
• CO2 and other gases ( 1% )

Question 4

how did oceans form?

Answer 4

as the Earth cooled, water vapour (produced by volcanic activity) condensed, falling as rain and filling up the hollows in the crust to form oceans.

Question 5

how was the amount of carbon dioxide in the earth’s early atmosphere reduced?

Answer 5

• photosynthesis of primitive green plants

- it dissolved into the oceans

Question 6

how did the oxygen levels in the atmosphere increase?

Answer 6

photosynthesis of plants

Question 7

what 3 things ensure that there is a state of approximate balance in the atmosphere?

Answer 7

• photosynthesis, which produces oxygen in the presence of sunlight, and uses carbon dioxide
• respiration and burning fuels, this uses oxygen and produces carbon dioxide
• carbon dioxide is absorbed by seas and oceans

Question 8

what evidence do scientists have that helped them to conclude:

• that there was little or no oxygen in the Earth’s early atmosphere, and
• that the amount of oxygen within the atmosphere has increased over time?

Answer 8

• oxygen is not released by volcanoes
• Venus and Mars have similar atmospheres made up of carbon dioxide
• fossil evidence from early rock shows the existence of photosynthesising organisms
• the composition of iron compounds is different within different types and ages of rock

Question 9

during photosynthesis, what do carbon dioxide and water get converted into?

Answer 9

glucose and oxygen

Question 10

what insoluble compound was formed when carbon dioxide reacted with other substances in the sea?

Answer 10

calcium carbonate

Question 11

what soluble compound was formed when carbon dioxide reacted with other substances in the sea?

Answer 11

calcium hydrogencarbonate

Question 12

for how long are the levels of carbon dioxide in the atmosphere generally thought to have remained in balance for?

Answer 12

at least 200 million years

Question 13

describe the stages of the carbon cycle

Answer 13

• PHOTOSYNTHESIS occurs in plants, removing carbon dioxide from the atmosphere
• RESPIRATION occurs in plants and animals, releasing carbon dioxide into the atmosphere
• DECOMPOSITION occurs in dead animals and plants, and microorganisms feed on the waste, releasing carbon dioxide as they respire
• COMBUSTION of fossil fuels occurs, releasing carbon dioxide into the atmosphere

Question 14

what is global warming?

Answer 14

global warming is the gradual increase in temperature of the Earth’s atmosphere

Question 15

what causes global warming?

Answer 15

the greenhouse effect; greenhouse gases (CO2, water vapour, nitrous oxide, methane) trap energy from the Sun in the Earth’s atmosphere, increasing the temperature

Question 16

the level of greenhouse gases in the atmosphere has gradually increased due to…

Answer 16

• burning fossil fuels (carbon dioxide, suflur dioxide, which can cause acid rain, and carbon monoxide)
• transportation (carbon dioxide, sulfur dioxide and carbon monoxide)
• cattle farming (methane)
• deforestation (carbon dioxide due to less photosynthesis)

Question 17

what is the correct process of photosynthesis?

a) carbon dioxide + glucose ➝ water + oxygen
b) carbon dioxide + water ➝ glucose + oxygen
c) oxygen + glucose ➝ carbon dioxide + water

Answer 17

b) carbon dioxide + water ➝ glucose + oxygen