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Science C1 Topic 1
GCSE edexcel core science chemistry: the earth and atmosphere
| Question | Answer |
|---|---|
| What is believed to have formed the early atmosphere? | Volcanic activity |
| What gases made up the Earth's early atmosphere? | Carbon dioxide, ammonia, water vapour, methane |
| How were the oceans formed? | 1. as the earth cooled, water vapour condensed into the oceans 2. commets (ice and rock) hit the earth and the ice melted into water |
| How was the amount of carbon dioxide in the early atmosphere reduced? | 1. it dissolved into the oceans 2. primitive life used it in photosynthesis 3. organisms developed shells made of calcium carbonate |
| Why did the amount of oxygen in the atmosphere increase? | It was given out by photosynthesis of primitive life |
| How do you investigate the proportion of oxygen in today's atmosphere? | Pass a known amount of air over hot copper- then measure the amount of air a few minutes later. The decrease in amount of air is the amount of oxygen (as it reacted with the copper to form copper oxide). |
| What are the proportions of gases in today's atmosphere? | Nitrogen- 78% Oxygen- 21% Argon- 0.9% Carbon dioxide- 0.04% Other gases- traces |
| Why is the composition of gases in the earth's atmosphere gradually changing? | 1. Volcanic activity - which releases gases like carbon dioxide 2. Human activity - such as cow farming (producing methane) and burning of fossil fuels (producing carbon dioxide) |
| Why is it difficult to be precise about the evolution of the atmosphere? | Because there are lots of different sources of information about the development of the atmosphere, but they are all limited |
| What planets have a similar atmosphere now to what scientists believe the early earth once had? | Mars and venus |
| Why do scientists believe that the early earth had no oxygen? | Because oxygen is not released by volcanic activity |
| Why was limestone created? | when organisms that had made their shells out of calcium carbonate died, their shells fell and became sediment- which built up creating the sedimentary rock |
| How did the amount of nitrogen in the earth's atmosphere increase? | Volcanoes gave out nitrogen-containing compounds that reacted to form nitrogen |
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