Chemistry AQA Paper 2

This question is about the Earth’s atmosphere. box

How long ago was the Earth formed?

• 4.6 billion years ago

• 4.6 million years ago

• 4.6 thousand years ago

Calculate the percentage X of other gases in the Earth’s atmosphere.

Use Table 1

The percentage of carbon dioxide in the Earth’s early atmosphere decreased.

Which two processes caused this decrease?

• Carbon dioxide dissolving in sea water

• Combustion of fossil fuels

• Farming of animals

• Formation of sedimentary rocks

• Volcanoes releasing carbon dioxide

Photosynthesis also decreased the percentage of carbon dioxide in the Earth’s early atmosphere.

Photosynthesis increased the percentage of another gas.

Complete the word equation for photosynthesis.

^__________+ water → glucose +^_________

Complete the sentence.

Scientists are not certain about the percentages of gases in the Earth’s early atmosphere because there is a lack of______

What equipment should the student use to measure:

• the mass of the evaporating dish

• the volume of sea water?

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The salt must be completely dry.

Which two extra steps are needed to show that the salt is completely dry?

• Filter the sea water again.

• Heat the evaporating dish and salt again.

• Measure the 50 cm3 of sea water again.

• Measure the mass of the empty evaporating dish again.

• Measure the mass of the evaporating dish and salt again.

Students Y and Z boil the same volume of sea water for the same period of time.

Explain why student Y collects a smaller volume of water than student Z.

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Water obtained by distillation does not need to be sterilised and is safe to drink.

Suggest why.

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