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17 Cards in this Set
- Front
- Back
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Why do different parts of Britain have different chemicals in their tap water? |
Due to the types of rock the water comes into contact with. |
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The rocks contain salts, some of which are soluble. What do soluble salts release into the water? |
Ions into the water when they dissove |
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Give two examples of soluble salts that commonly get into the water supply. |
1. magnesium sulphate 2. calcium sulphate |
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What is water containing soluble salts referred to as? |
Hard water |
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If the water does not come into contact with rocks that contain soluble salts, what is the water referred to as? |
Soft water |
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What does hard water cause and where? |
Limescale in electric kettles and washing machines |
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Do you need to use more soap if you have hard or soft water? |
Hard |
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Does hard or soft water lather easier with soap? |
Soft |
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What are the six steps that explain another way in which salts can be dissolved in water. |
1. CO2 from the atmosphere dissolves in water droplets in the clouds 2. this forms carbonic acid (a weak acid) 3. acidic raindrops fall onto rocks containing calcium carbonate 4. the acid and calcium carbonate react to form calcium hydrogencarbonate 5. this is soluble and will dissolve causing hardness 6. water collected in a reservoir
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Which rocks contain calcium carbonate? |
Marble and limestone |
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Which rocks contain magnesium carbonate? |
Dolomite |
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Why does water become hard when it has come into contact with carbonate rocks? |
The rocks release the hydrogencarbonate ion into the water |
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Give two ways to tell whether water is hard or soft
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1. Heat it 2. See how it behaves with soap |
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What happens when hard water is heated? |
The hydrogen carbon ion is broken down into CO2, hydrogen and the carbonate ion.
Calcium ions present in the water will combine with the carbonate ion to form calcium carbonate, an insoluble substance, that is deposited as limescale.
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Hard water has calcium and magnesium ions. These react with ions in soap to form... |
An insoluble precipitate - a solid called scum. |
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Soft water does not contain these metal ions so... |
all the ions in the soap are available to form a lather and do the job of cleaning. |
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What does how hard the salt is depend on? |
How much salt is dissolved |
