earth and atmospheric science past paper 1

Question 1

state how cooling changed the composition of the earth’s atmosphere

Answer 1

as the earth cooled down, most of the water vapour condensed and formed the oceans

Question 2

explain how photosynthesis changed the composition of the Earth’s atmosphere

Answer 2

photosynthesis caused the removal CO2 from the air and the release of oxygen. this decreased the amount of CO2 and the amount of oxygen in the atmosphere gradually increased

Question 3

write the balanced equation for the reaction of copper with oxygen

Answer 3

2Cu + O2 - 2CuO

Question 4

When the copper has reacted with all the oxygen, the apparatus is allowed to cool.
The initial volume of dry air in the apparatus was 50 cm3, measured at room temperature and pressure.
During the experiment the volume of gas in the apparatus decreased.
Calculate the final volume of gas remaining in the apparatus after allowing it to cool to room temperature.
(percentage of oxygen in dry air is 21%)

Answer 4

21 x 50 / 100 = 10.5cm(cubed)
50 - 10.5 = 39.5

Question 5

After the reaction between dry air and copper is complete, most of the gas remaining in the apparatus is
A. argon
B. carbon dioxide
C. nitrogen
D. oxygen

Answer 5

nitrogen

Question 6

The percentage of oxygen in the atmosphere has increased since the Earth’s earliest atmosphere.
Describe the process that has caused this change.

Answer 6

photosynthesis causes for plants to absorb carbon dioxide and releases oxygen

Question 7

test for oxygen

Answer 7

a glowing splint relights

Question 8

state why an excess of copper must be used

Answer 8

to ensure all the oxygen is removed

Question 9

explain how this experiment can be used to find the volume of oxygen in 100cm(cubed) of air

Answer 9

• measure the volume of gas in the syringe at the end of the experiment
• subtract from 100cm(cubed)/original volume) to give volume of oxygen

Question 10

what is the percentage of carbon dioxide in the earth’s atmosphere today

Answer 10

less than 0.5%

Question 11

The percentage of carbon dioxide in the Earth’s atmosphere today is less than that in the Earth’s earliest atmosphere.
Explain what has caused the percentage of carbon dioxide to decrease.

Answer 11

CO2 was used by plants for photosynthesis as they continued to grow dissolved in the oceans and formed fossil fuels

Question 12

how do the atmospheric gases help to keep the earth warm?

Answer 12

reflects heat back to earth