Hard Water

Question 1

What type of water forms lather with soap?

Answer 1

Soft water.

Question 2

What type of water forms scum with soap?

Answer 2

Hard water, more soap is needed to form lather.

Question 3

What dissolved compounds are in hard water?

Answer 3

Calcium and Magnesium.

Question 4

How do dissolved compounds get into hard water?

Answer 4

When water comes into contact with rocks.

Question 5

What are the two types of hard water?

Answer 5

Permanent hard water and Temporary hard water.

Question 6

What happens to permanent hard water when it is boiled?

Answer 6

It stays hard.

Question 7

What happens to temporary hard water when it is boiled?

Answer 7

It is softened.

Question 8

How does boiling temporary hard water soften it?

Answer 8

The hydrogencarbonate ions in temporary hard water decompose on heating to produce carbonate ions which react with calcium and magnesium ions to form precipitates.

Question 9

How can hard water increase costs?

Answer 9

Because more soap is needed.

Question 10

What are the disadvantages of temporary hard water?

Answer 10

They decrease the efficiency of heating systems and kettles, when scale is deposited.

Question 11

What are the benefits of hard water?

Answer 11

Calcium compounds found in hard water are good for the development and maintenance of bones and teeth and also help to reduce heart disease.

Question 12

How can hard water be made soft?

Answer 12

By removing the dissolved calcium and magnesium ions.

Question 13

What are the 2 methods to make hard water soft?

Answer 13

The calcium and magnesium ions react with sodium carbonate to form a precipitate of calcium carbonate and magnesium carbonate.
or
Commercial water softeners such as ion exchange columns containing hydrogen ions or sodium ions, which replace the calcium and magnesium ions when hard water passes through the column.

Question 14

For humans drinking water should have sufficiently low levels of _________ _____ and ________.

Answer 14

Dissolved salts and microbes.

Question 15

How do you get water of the correct quality for humans?

Answer 15

Choosing an appropriate source.
Passing the water through filter beds to remove any solids.
Sterilising with chlorine.

Question 16

What do water filters contain?

Answer 16

Carbon, Silver and Ion Exchange resins.

Question 17

What do water filters do?

Answer 17

Remove some dissolved substances from tap water to improve the taste and quality.

Question 18

Why may chlorine be added to drinking water?

Answer 18

To reduce microbes.

Question 19

Why may fluoride be added to drinking water?

Answer 19

To improve dental health.

Question 20

How can pure water be produced?

Answer 20

By distillation.

Question 21

What are the advantages of fluoride being added to drinking water?

Answer 21

Adding fluoride to public water supplies has been credited with being responsible for the decline in tooth decay.
The World Health Organization points out that benefits are greatest for the economically disadvantaged, who often don’t have access to adequate dental care.

Question 22

What are the disadvantages of fluoride being added to drinking water?

Answer 22

Consumption at higher levels over time has been proven to cause painful bone disease.
Fluoride can cause dental fluorosis, or browning and pitting of the teeth, in young children.
Extensive studies have shown a surprising similarity in increased dental health in both communities with and without fluoridated water.
It follows that the decrease in tooth decay may be because of an improvement in dental health care, earlier intervention, and the prevalence of fluoride in toothpastes and other mouth products.