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18 Cards in this Set
- Front
- Back
Describe the difference between soft water and hard water when reacted with soap |
Soft water easily forms lather with soap Hard water reacts with soap to form scum |
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Which dissolved ions usually cause hard water? |
Calcium ions Magnesium ions |
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What are the two types of hard water? |
Temporary Permanent |
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Explain the differences between temporary hard water and permanent hard water |
Temporary can have its hardness removed by boiling Permanent remains hard even after boiling |
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Which dissolved ions does temporary hard water contain? |
Hydrocarbonate |
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Give 2 reasons why using hard water costs more money |
More soap is needed Heating temporary hard water produces scale which reduces the efficiency of heating systems |
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Give 2 health benefits of drinking hard water |
Good for the development of bones and teeth Help reduce heart disease |
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Give 2 ways permanent hard water can be made soft |
By adding sodium carbonate Using an ion exchange column |
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Explain how sodium carbonate makes water soft |
The soluble carbonate ions precipitate out calcium and magnesium ions to form insoluble carbonates |
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Explain how an ion exchange column works |
Hard water passes through the column Sodium ions in the column are exchanged for the calcium or magnesium ions in the hard water |
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Describe how a water filter works |
Carbon reduces levels of chlorine, pesticides and other inorganic compounds Ion exchange resin removes calcium, magnesium, lead, copper and aluminium ions Silver particles discourage growth of bacteria in the filter |
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Why is chlorine added to drinking water? |
To kill microbes |
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Give 2 arguments against using chlorine in drinking water |
Some people feel it could be a risk to their health Can react with organic molecules to form toxic compounds |
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What alternative gas can be used to sterilise swimming pools? |
Ozone |
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Give 3 benefits of adding fluorine to drinking water |
Helps reduce tooth decay No harmful effects Only tiny amounts added |
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Give 3 arguments against adding fluorine to drinking water |
Can be linked to weakening of bones People don't have a choice Safe limits cannot be set |
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Describe how pure water can be produced by distillation |
Impure water sample is boiled and evaporates Steam is condensed back into a liquid using a condenser Pure water is collected |
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What is the main disadvantage of producing pure water by distillation? |
Larger amounts of energy needed meaning large costs |