C3-Hard and soft Water

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  • Created by: Heather
  • Created on: 10-05-14 14:40
What is hard water?
It contains dissolved minerals like calcium and magnesium ions that make it difficult to produce a lather,
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What is soft water?
It contains sodium ions and no calcium or magnesium ions and it is easier to produce a lather,
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How does water become hard?
By the rocks which the water runs through-some contain more calcium + magnesium ions
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How is scum formed?
Scum is formed when soap reacts with hard water from the insoluble calcium and magnesium ions,
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How is limescale formed?
When hrd water decomposes to form limescale or calcium carbonate
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Why is scale bad?
It is a poor conductor of electricity so reduces the efficency of thw product as it uses more energy,
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What are the advantages of hard water?
Calcium ions help develop teeth and bones and evidence it reduces heart disease,
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What is water called when its hardness can be rfemoved by boiling?
Temporary hard water,
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What ions does temporary hard water contain?
Hydrogen carbonate ions
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What does the hydrogen carbonate ions decompose to form when heated?
Carbonate ions
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What us permanent hard water?
Hardness can't be removed by boiling
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What ions permanent hard water contain other than calcium +magnesium?
Sulfate ions
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What are teo methods of softening hard water?
Washinf soda (sodium carbonate) or an ion exchange column,
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What is the equation for adding sodium carbonate to hard water?
Calcium + Sodium Carbonate -> Calcium carbonate,
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What does an ion exchaneg column contain?
A column packed with resin balls which has sodium ions attached to it,
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waht happens when hard water is passed through the ion exchange column?
The sodium ions are excahnged for the calcium and magnesium ions and as these ions are removed, the water is made soft,
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What is the problem with ion excahneg columns?
they have to topped up with sodium ions often to replenish the sodium ions so thye can be exchange with more calcium and magnesium ions,
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What is the first stage of cleanig water?
Water is passed throgh screens to stop large objects like twigs and sticks from entering,
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What is the second stage of cleaning water?
The water is passed through a filter bed which is made of sand and gravel and removes insoluble materials,
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What is the third stage of cleaning water?
Sedimentation tank whete aluminium sulfate is added to the water so the smaller paticles clump together to form larger molecules which sink to the bottom,
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what is the fourth stage of cleanign water?
Water is passed through a fine filter made of carbon granules which removes the alst of any insoluble materials,
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what is the fifth and final stage of cleaning the watyer?
Chlorine is added to the water to kill pathogens in the water
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Why do some people argue flourine should be added to water?
To improve dental health by reducing tooth decay, -Areas have flourinated water and there has been no harmful side ffects, -Bacteria of tooth decay can cause heart disease so protection, -Flourien only added in small amounts,
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Why do some people argue flourine shouldnt be added to water?
It is said to lead to teeth staining, pain and bone disease and is unethical as you can't choose, -Can't set safe limits of flourine as can't control water intake, -Flourine can affect brain
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Other cards in this set

Card 2

Front

What is soft water?

Back

It contains sodium ions and no calcium or magnesium ions and it is easier to produce a lather,

Card 3

Front

How does water become hard?

Back

Preview of the front of card 3

Card 4

Front

How is scum formed?

Back

Preview of the front of card 4

Card 5

Front

How is limescale formed?

Back

Preview of the front of card 5
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