C3 Water

What is the difference between hard water and soft water?

Soft water easily produces a lather with little soap. Hard Water requires more soap to produce lather and produces scum

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Why does hard water need more soap to produce a lather?

Hard water contains dissolved compound that react with soap to form an insoluble solid called scum.

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What are the dissolved substances in hard water?

Calcium and magnesium ions

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When magnesium ions and calcium ions react with water, what is produced?

Scum

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When temporary hard water is heated, what is formed?

Scale

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What are the disadvantages of scale?

They can reduce efficiency of heating systems and cause blockages as they deposit in kettles, boilers and pipes.

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What is the difference between scale and scum?

Scum is formed when soap reacts with dissolved compounds in water. Scale is produced when temporary hard water is boiled or heated.

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Why is it better to drink hard water than soft water?

Calcium sompounds are good for health, helping to develop strong bones and teeth. Calcium can reduce heart disease.

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How is hard ward water made soft?

By removing calcium and magnesium ions which react with salt

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How is temporary hard water softened?

By boiling because when it is heated the magnesium and calcium ions form an insoluble solid called scale, which can be removed form water.

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What ions do temporary hard water contain?

Hydrogencarbonate ions, HCO3

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What does hydrogencarbonate decompose to?

Carbonate ions, water and carbon dioxide

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What is produced when carbonate ions from decomposed hydrogen carbonate react with magnesium and calcium ions?

Magnesium carbonate and calcium carbonate, which are deposited as scale

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Aside from heating, what are the 2 other ways of softening hard water?

1. Precipitating out the ions that cause hardness with sodium carbonate 2. ion-exchange column

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How does sodium carbonate (washing powder) soften hard water?

The sodium carbonate reacts with calcium ions and magnesium ions in the water to form solid calcium carbonate and magnesium carbonate which cannot react with soap.

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Describe how to soften hard water using an ion-exchange column

1. exchange columns are packed with resin containing either sodium or hydrogen ions 2. Calcium and magnesium ions attached to the resin 3. Sodium and hydrogen ions take their place in water. 4 sodim adn hydrogen ions do not react with soap.

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How is drinking water treated to make it safe to drink?

1. Sedimentation - treated 2. Filration - Remove solids 3. Disinfection - kill microbes in the water.

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What is used to kill microbes in drinking water?

Chlorine

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How is the taste of water improved?

1. Water filetrs contain carbon and ion-exchange resin that remove soluble substances and silver or another substance to prevent growth.

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How can pure water be made?

Through distillation

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Why is distillation not used to treat mains tap water

It requires a large amount of water to boil water, and so it would be expensive to do it on a large scale.

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What are the disadvnatges of hard water?

Causes problems with heating systems and with washing.

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What is an advantage of hard water?

Drinking hard water has benefits

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What are the pros of cons of using chlorine in water?

+ Chlorine is particularly effective in killing microbes in water so that it is safe to use. - Chlorine is poisonious and it can produce other toxic compounds.

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C3 Water

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Other cards in this set

Card 2

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Card 3

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Card 4

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Card 5

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Back

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