earth and atmospheric science past paper 1 Flashcards
state how cooling changed the composition of the earth’s atmosphere
as the earth cooled down, most of the water vapour condensed and formed the oceans
explain how photosynthesis changed the composition of the Earth’s atmosphere
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
write the balanced equation for the reaction of copper with oxygen
2Cu + O2 - 2CuO
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%)
21 x 50 / 100 = 10.5cm(cubed)
50 - 10.5 = 39.5
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
nitrogen
The percentage of oxygen in the atmosphere has increased since the Earth’s earliest atmosphere.
Describe the process that has caused this change.
photosynthesis causes for plants to absorb carbon dioxide and releases oxygen
test for oxygen
a glowing splint relights
state why an excess of copper must be used
to ensure all the oxygen is removed
explain how this experiment can be used to find the volume of oxygen in 100cm(cubed) of air
- 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
what is the percentage of carbon dioxide in the earth’s atmosphere today
less than 0.5%
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.
CO2 was used by plants for photosynthesis as they continued to grow dissolved in the oceans and formed fossil fuels
how do the atmospheric gases help to keep the earth warm?
reflects heat back to earth