1. Core Chemistry Smart 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 EarthThe 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 Early EarthThe Earth Today No oceansOceans Why? The Earth cooled down and water vapour condensed

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

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

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

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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

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