Water

Question 1

What two elements makes up the compound water?

Answer 1

Hydrogen and oxygen

Question 2

Why is it difficult to find pure water?

Answer 2

Water is an excellent solvent

Question 3

Give six properties of water

Answer 3

Freezing point 0°C
Boiling point 100°C
Excellent solvent
Colourless and odourless liquid
Turns copper sulphate from white to blue
Turns cobalt chloride paper from blue to pink

Question 4

Name four stages in the water cycle

Answer 4

Evaporation
Condensation
Precipitation
Run down back to the sea after relief rainfall

Question 5

What are typhoid and cholera

Answer 5

Diseases resulting from untreated water

Question 6

Name the five stages of water treatment

Answer 6

Screening
Settling
Filtration
Chlorination
Fluoridation

Question 7

Give a rhyme to remeber the five stages of screening

Answer 7

Silly Shane Follows Chelsea Football

Question 8

Explain what happens during screening

Answer 8

Passing water through a wire/screen to remove floating material from water

Question 9

Explain what happens during settling

Answer 9

Aluminium sulphate is added and gathers smaller insoluble solids to the bottom of the tank

Question 10

Explain what happens during filtration

Answer 10

Water passes through sand to remove remaining insoluble particles

Question 11

Explain what happens during chlorination

Answer 11

Chlorine is added and kills any bacteria present

Question 12

Explain what happens during fluoridation

Answer 12

Fluorine is added (only in certain countries) to prevent tooth decay from drinking water

Question 13

Explain electrolysis

Answer 13

The splitting up of a compound by passing electricity through it

Question 14

What is the tubing used for electrolysis called

Answer 14

Hoffman Voltameter

Question 15

How much oxygen compared to hydrogen is produced when water is split

Answer 15

H2O releases 2 hydrogen atoms for every oxygen atom so there is twice as much hydrogen

Question 16

Give the chemical formula for the splitting of water

Answer 16

2H20 —–> 2H2+O2

Question 17

Why do water pipes burst in the cold

Answer 17

Water expands after it is cooled past 4°C

Question 18

Explain miniscus

Answer 18

Curved surface of a liquid when in an object or vessel

Question 19

Explain desalination

Answer 19

Process where water is obtained from sea water

Question 20

Why would soap be added to water

Answer 20

For washing, to help it to dissolve tougher substances such as grease and oil

Question 21

Explain hard water

Answer 21

Water that does not lather easily with soap

Question 22

Explain soft water

Answer 22

Water that lathers easily with soap

Question 23

Give a word equation for the forming of scum

Answer 23

Calcium ions + soap = scum

Question 24

What causes water hardness?

Answer 24

Caused by presence of magnesium and calcium ions in the water

Question 25

Explain how limescale forms

Answer 25

When hard water is heated it deposits white insoluble solid called limescale on pipes

Question 26

Three ways which water can be softened

Answer 26

Ion exchange
Distillation
Boiling

Question 27

Give the advantages to hard water

Answer 27

Good source of calcium
Most people prefer the taste
Good for brewing/tanning

Question 28

Disadvantages to hard water

Answer 28

Limescale blocks pipes of ex. Kettle
Wastes soap
Produces scum with soap.