Water

Question 0

Describe the test that can be carried out to test for the presence of water

Answer 0

Cobalt chloride paper turns from blue to pink in the presence of water

Question 1

Name the two elements that make up a compound of water and give the composition

Answer 1

Hydrogen and oxygen , 2 hydrogens and 1 oxygen

Question 2

What is soft water ?

Answer 2

Water that easily forms a lather with soap.

Question 3

What is hard water ?

Answer 3

Water that does not easily form a lather with soap .

Question 4

What causes hardness?

Answer 4

The presence of calcium ions dissolved in the water

Question 5

How can hardness be removed ?

Answer 5

By passing the water through an ion exchange resin

Question 6

Give the two advantages of hard water

Answer 6

1) good source of calcium for strong bones and teeth

2) hard water taste better than soft water

Question 7

Give the two disadvantages of hard water

Answer 7

1) wastes soap and leaves a scum

2) limescale blocks pipes and reduces the efficiency of kettles and washing machines

Question 8

What is the boiling point for water ?

Answer 8

100C

Question 9

What is the freezing point for water ?

Answer 9

0C

Question 10

Name the five stages for the treatment of water( Sabrina screamed for clothing funds )

Answer 10

Screening
Settling
Filtration
Chlorination 
Fluoridation

Question 11

Describe screening

Answer 11

Removes large debris by passing water through a wire mesh

Question 12

Describe settling

Answer 12

Aluminium sulphate is added to the water , it makes the particles stick together

Question 13

Describe filtration

Answer 13

Very small dirt particles are removed through filtration

Question 14

Describe fluoridation

Answer 14

In Ireland fluorine is added to prevent tooth decay

Question 15

How does an ion exchange resin remove hardness

Answer 15

It replaces the ions in the hard water that cause hardness with ions that dont . The water then becomes soft water or deionised water

Question 16

What is electrolysis ?

Answer 16

The production of a chemical reaction through electricity

Question 17

What is a Hoffman voltameter ?

Answer 17

It is used to pass a current through water causing it to break down into hydrogen and oxygen

Question 18

Why is sulfuric acid added to water ?

Answer 18

To help it to conduct electricity

Question 19

What is the test for hydrogen ?

Answer 19

It burns with a ‘pop’

Question 20

What is the test for oxygen ?

Answer 20

Relights a glowing splint

Question 21

Why is there twice as much hydrogen than oxygen produced ?

Answer 21

Because each water molecule has two hydrogens atoms for every oxygen atom

Question 22

Describe a test that distinguishes between hard and soft water

Answer 22

1) pour water from the various samples into different test tubes
2) make sure to use the same amount of water in each test tube to make it a fair test
3) add the same number of soap flakes to each test tube to also make it a fair test
4) shake the mixture
5) explain what test tube forms a lather
6) a lather will form in the test tube containing soft water and no lather will form in the test tubes containing hard water