Water Purification
Q1.
The diagram shows three stages in the treatment of reservoir water.
 
(a)     (i)      What is separated from the reservoir water during filtration?
Tick (✔) one box.
Bacteria		
Dissolved nitrates		
Solids		
(1)
(ii)     What is added to sterilise the water?
Tick (✔) one box.
Calcium		
Chlorine		
Magnesium		
(1)
(iii)    State one advantage of adding fluoride to drinking water.
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(1)
(b)     The diagram shows a water filter used in the home.
Water in
 
A student collected a sample of water from the filter.
The student could show that the filtered water contains dissolved salts without using a chemical test.
Describe how.
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(2)
(c)     Seawater is forced through a membrane to make drinking water.
Seawater
             
Drinking water
Suggest why water molecules can pass through the membrane, but sodium ions and chloride ions cannot.
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(1)
(Total 6 marks)