Water

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Lathering propeties of soft water
Readily forms lather with soap
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Lathering propeties of hard water
react with soap to form scum so more soap is needed to form lather
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Soapless detergents
do not form scum
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Dissolved compounds in hard water
calcium and magnesium
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How dissolved compounds enter water
when water comes into contact with rocks
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Permanent hard water
remains soft when boiled
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Temporary hard water
is softened by boiling
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Method to distinguish between permanent and temporary hard water
Add soap solution to sample of water until permanent lather achieved for set time period, boil sample of same size and add soap solution until permanent lather achieved for same amount of time as first test, temporary needs less soap (is softened)
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Method to measure hardness of water by titration
Soap solution added to sample of hard water and amount required to achieve a permanent lather measured. The more solution needed, the harder the water.
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Why is temporary hard water temporary?
Contains hydrogencarbonate ions that decompose on heating to produce carbonate ions, which react with calcium and magnesium to form precipitates (scale), removing them from water
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Why is permanent hard water permanent?
Calcium ions contained in a salt that isn't removed by boiling (calcium sulfate)
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Why can hard water increase costs?
More soap is needed. When temporary hard water is heated, scale is produced which reduces the efficiency of heating systems and kettles
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Benefits of hard water
Calcium compounds good for development bones and teeth and help reduce heart disease
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How hard water can be made soft using sodium carbonate
Sodium carbonate (washing soda) reacts with calcium and magnesium ions to form a precipitate of calcium carbonate and magnesium carbonate
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How hard water can be made soft using commerical water softeners such as ion exchange columns
Exchange colums contain resin containing hydrogen or sodium ions which replace calcium and magnesium ions when water passes through the column. Mg and Ca ions remain in resin. Resin replaced when it runs out of ions.
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Water of the correct quality is essential for life. Required propeties of drinking water
sufficiently low levels of dissolved salts and microbes
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How is water of the correct quality produced?
Choosing an appropraite source, passing it through filter beds to remove any solids, sterilising with chlorine
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How can tap water be improved in taste and quality?
Filters containing carbon, silver and ion excange resins (with H and Na ions) can remove dissolved substances from tap water
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Why is chlorine added to drinking water?
To reduce microbes
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Advantages and disadvantages of adding fluoride to water
Strengthen tooth enamel and protect against decay, some people believe it's toxic and can cause disease, and that we don't need anymore as it's in toothpaste
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Pure water can be produced by distillation. Issue?
Uses lots of energy so can be very expensive
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Other cards in this set

Card 2

Front

Lathering propeties of hard water

Back

react with soap to form scum so more soap is needed to form lather

Card 3

Front

Soapless detergents

Back

Preview of the front of card 3

Card 4

Front

Dissolved compounds in hard water

Back

Preview of the front of card 4

Card 5

Front

How dissolved compounds enter water

Back

Preview of the front of card 5
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