1. Core Chemistry Big Teach 1: The Atmosphere

2. Key terms used in exam questions
Abundant – most common
Composition – how much of each gas is present

3. Why don’t we know what the early atmosphere was like?
Nobody was there
No measurements were taken
Different sources conflict

4. The Early Earth
The Earth Today
The early Earth was rocky and dry
The gases in the atmosphere came from volcanoes
The most abundant gasses were:
Carbon dioxide
Water Vapour
The Earth today contains oceans
The most abundant gasses in dry air are:
Nitrogen: 78%
Oxygen: 21%
Carbon dioxide 0.04%
Argon 0.9%

5. The Earth cooled down and water vapour condensed
The Early Earth
The Earth Today
The Earth cooled down and water vapour condensed
No oceans
Oceans
Why?

6. Carbon dioxide dissolved in the oceans
The Early Earth
The Earth Today
Carbon dioxide dissolved in the oceans
Lots of Carbon dioxide
Less carbon dioxide
Why?

7. No oxygen 21% Oxygen Why? The Early Earth The Earth Today
Plants evolved and carried out photosynthesis: Take in carbon dioxide give out oxygen
No oxygen
21% Oxygen
Why?

8. Questions

9. Answers

10. The amount of carbon dioxide does change in todays atmosphere!
The Earth Today
Increasing Carbon dioxide:
Burning fossil fuels
Volcanic eruptions
Deforestation
Respiration
Decreasing Carbon Dioxide:
Dissolving in the Oceans
Photosynthesis
The amount of carbon dioxide does change in todays atmosphere!
WHY?
The Earth today contains oceans
The most abundant gasses in dry air are:
Nitrogen: 78%
Oxygen: 21%
Carbon dioxide 0.04%
Argon 0.9%

11. Questions

12. Answers

13. Exam Questions on percentage gases
Questions where you are asked to calculate the percentage of oxygen in the experiment
If asked why the volume of gas decreased:
The (Metal) reacted with the oxygen to form (metal) oxide. The (water/syringe) moved to take the place of the oxygen.
If asked to calculate the % of oxygen
(Change in volume/Total volume) x 100

14. Exam Questions on percentage gases
Questions where you are asked to calculate the volume of gas remaining after the oxygen had been removed
(Total volume/100) X 79

15. Exam Questions on percentage gases
Questions where you are asked the most abundant gas remaining after an experiment
THE ANSWER IS ALWAYS NITROGEN

16. Exam Questions on percentage gases
Questions where you are asked to write the word equation
THE ANSWER IS usually in the question

17. Questions

18. Answers