6.3 Interpreting and interacting with earth systems

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Question 36

A water-treatment works tests stream water before and after treatment. The results are shown in the table.

Treatment	Insoluble particles (mg/dm³)	Harmful microorganisms (per cm³)
None	48	120
Filtration only	5	118
Filtration followed by chlorination	5	1

Use the results to explain why the water is filtered and then chlorinated rather than only filtered.

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Markscheme

6.3 Interpreting and interacting with earth systems Questions

GCSE
Chemistry
6.3 Interpreting and interacting with earth systems

109 exam-style questions on OCR GCSE Chemistry 6.3 Interpreting and interacting with earth systems, covering 6.3.1 Formation and evolution of the atmosphere, 6.3.2 The greenhouse effect and climate change, 6.3.3 Sources and problems of atmospheric pollutants, and 6.3.4 Producing potable water. Each one has a worked solution and a mark scheme showing where the marks go.

Question bank·6.3 Interpreting and interacting with earth systems