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Fill in the gaps - use the helpsheet!

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Correct the mistakes

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How to Balance Chemical Equations in 5 Easy Steps: Balancing Equations Tutorial

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You need to be able to identify elements from their symbols...

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See if you can balance these

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This is an example of a 6 mark question that could come up...

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evolution of the atmosphere - Google Search

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The atmosphere has not always been the same. It has been much the same, but nevertheless now contains more nitrogen and oxygen, and less carbon dioxide, than it did when the earth first formed. Recently, the addition of greenhouse gases such as carbon dioxide from burning fossil fuels has lead to global warming.

It is difficult to predict, even by using computer models, exactly what the mean temperature of the Earth will be in the future. However it seems sensible to limit global warming and protect the environment, through sustainable development and by reducing waste, wherever possible.

Scientists believe that the Earth was formed about 4.5 billion years ago. Its early atmosphere was probably formed from the gases given out by volcanoes. It is believed that there was intense volcanic activity for the first billion years of the Earth's existence.

The early atmosphere was probably mostly carbon dioxide, with little or no oxygen. There were small quantities of water vapour, ammonia and methane. As the Earth cooled down, most of the water vapour condensed and formed the oceans.

Changes in the atmosphere

So how did the proportion of carbon dioxide in the atmosphere go down, and the proportion of oxygen go up?

The proportion of oxygen went up because of photosynthesis by plants.

The proportion of carbon dioxide went down because:

it was locked up in sedimentary rocks, such as limestone, and in fossil fuels

it was absorbed by plants for photosynthesis

it dissolved in the oceans

The burning of fossil fuels is adding carbon dioxide to the atmosphere faster than it can be removed. This means that the level of carbon dioxide in the atmosphere is increasing.

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The atmosphere has not always been the same. It has been much the same, but nevertheless now contains more nitrogen and oxygen, and less carbon dioxide, than it did when the earth first formed. Recently, the addition of greenhouse gases such as carbon dioxide from burning fossil fuels has lead to global warming.

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Gases in the Atmosphere

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National Geographic Our Atmosphere Earth Science

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GCSE BBC Science Bitesize - Changes to the Earth and Atmosphere

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This GCSE BBC Bitesize video is from the original programmes from 2000 that were broadcast on BBC2. It covers the areas of the chemistry foundation paper. Select the, "more from," or type jamjarmmx into your search for the other Chemistry clips as well as the Physics and Biology clips.

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