Q1.
The chemical compositions of two samples of hard water, A and B, are shown in the
table.
pH
Ions present:
(a)
Sample A
Sample B
9
8
Concentration in mg/litre
Ca2+
101
135
Mg2+
2
9
Na+
9
6
HCO3–
299
6
CI–
14
8
SO42–
5
136
NO3–
6
0
What does the pH value tell you about these samples?
.....................................................................................................................................
(2)
(b)
Use the information in the table to explain what is meant by hard water.
.....................................................................................................................................
.....................................................................................................................................
(1)
(c)
What would be the effect of using temporarily hard water in a kettle?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
Page 1
(d)
(i)
Explain which sample of water is permanently hard.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(ii)
How could this hardness be removed?
...........................................................................................................................
...........................................................................................................................
(1)
(e)
State one advantage of drinking hard water.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 10 marks)
##
A leaflet listed the effects of hard water:
HOW HARD WATER COSTS YOU HARD CASH
Hard water causes:
 Blocked showers, burnt out immersion heaters
 Scale build up inside water pipes
 Higher water heating cost
 Extra soap required to get a lather
Page 2
Describe how softening the hard water could save money.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(Total 3 marks)
Q3.
The label shows the ions present in the bottle of spring water. This water is
temporarily hard.
(a)
Name the compound that would be present in the greatest amount if this water
were evaporated to dryness.
.....................................................................................................................................
(2)
(b)
(i)
What is hard water?
...........................................................................................................................
...........................................................................................................................
(2)
Page 3
(ii)
State one advantage of hard water.
...........................................................................................................................
(1)
(c)
Describe an experiment that would show that this water is temporarily hard.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(d)
This hard water may be softened as shown.
What name is given to this process?
.....................................................................................................................................
(1)
(Total 10 marks)
Page 4
Q4.
Washing powders are a mixture of substances. The substances in a box of Kleenkwik
washing powder are shown.
(a)
Which substance in the washing powder gives clothes a pleasant smell?
....................................................................................................................................
(1)
(b)
What does a bleach do?
....................................................................................................................................
(1)
(c)
Sodium phosphate removes the hardness in water.
(i)
What is hard water?
.........................................................................................................................
.........................................................................................................................
(1)
(ii)
Why should the hardness be removed?
.........................................................................................................................
Page 5
.........................................................................................................................
(1)
(iii)
Give another method which removes the hardness in water.
.........................................................................................................................
.........................................................................................................................
(1)
(d)
Circle the chemical which is used to make detergents.
carbonic acid
hydrochloric acid
sulphuric acid
(1)
(Total 6 marks)
Q5.
Rainwater falling on limestone rocks can form caves.
(a)
Complete the sentences by choosing the correct words from the box.
acidic
alkaline
Page 6
dissolves
hard
reacts
soft
tastes
You may use each word once or not at all.
Rainwater is an ....................... solution which ....................... with limestone. The
solution formed in the lake is known as ....................... water. One advantage of
drinking the water from the lake is that it ....................... better than rainwater.
(4)
(b)
Samples of water were tested by shaking with soap solution. The results are shown
in the table.
Water sample (50 cm3)
Volume of soap solution
to form a lather in cm3
lake
15
boiled lake
3
rain
1
(i)
What is seen when only 10 cm3 of soap solution is shaken with 50 cm3 of
water from the lake?
...........................................................................................................................
(1)
(ii)
Why did the rainwater need only 1 cm3 of soap solution to form a lather?
...........................................................................................................................
(1)
(iii)
Why did the water from the lake need 15 cm3 of soap solution to form a lather?
...........................................................................................................................
(1)
(iv)
Explain why boiled water from the lake needed only 3 cm3 of soap solution to
form a lather.
Page 7
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(Total 9 marks)
Q6.
This information has been taken from two bottles of Australian spring water.
(a)
The labels show the names of the ions present in Ridgway and Homeland spring
waters.
Describe how these ions got into the water.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
Both Ridgway and Homeland spring waters are hard.
(i)
There are two ions shown on the labels which make these spring waters hard.
Page 8
Name one of these ions.
...........................................................................................................................
(1)
(ii)
Ridgway spring water is about twice as hard as Homeland spring water.
Use the information on the labels to explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(iii)
Describe how you could use soap solution to show that Ridgway spring water
is about twice as hard as Homeland spring water. You should state how the
experiment is made fair.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(Total 8 marks)
Q7.
Good quality water is needed for a healthy life.
In the United Kingdom, obtaining safe water for drinking is as simple as turning on a tap.
The water is made safe to drink by water companies.
However, in many parts of Africa and Asia, water used for drinking is contaminated and
untreated. It is estimated that 2.2 million people die each year as a result of drinking
contaminated water.
Page 9
DADA DANESHANANDA, Man with filtered water from the
Mafi-Zongo water project. www.amurt.net/africa/ghana/2005
Efforts are being made to solve this problem and more water is being treated.
Describe how water in the United Kingdom is treated.
Explain how this makes it safe to drink.
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
(Total 3 marks)
Q8.
Good quality water is needed for a healthy life.
In the United Kingdom, obtaining safe water for drinking is as simple as turning on a tap.
The water is made safe to drink by water companies.
However, in many parts of Africa and Asia, water used for drinking is contaminated and
Page 10
untreated. It is estimated that 2.2 million people die each year as a result of drinking
contaminated water.
DADA DANESHANANDA, Man with filtered water from the
Mafi-Zongo water project. www.amurt.net/africa/ghana/2005
(a)
Sea water is not used as drinking water.
Suggest why.
....................................................................................................................................
....................................................................................................................................
(1)
(b)
Explain why water for drinking is filtered and then treated with chlorine.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(Total 3 marks)
Q9.
Two problems of hard water are scale and scum, as shown in the pictures of a
heating element and a wash basin.
Page 11
(a)
Explain the difference between scale and scum
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
Explain how hard water can be made soft using an ion-exchange column.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 4 marks)
Q10.
Two problems of hard water are scale and scum, as shown in the pictures of a
heating element and a wash basin.
Page 12
(a)
Name one ion that causes water to be hard.
.....................................................................................................................................
(1)
(b)
Hard water can be softened using an ion-exchange column.
Complete this sentence by choosing the correct word from the box.
aluminium
copper
sodium
When hard water passes through the column, the ions that cause hardness are
exchanged for .................................................. ions, and soft water is produced.
(1)
(c)
Describe how soap solution can be used to show that the water going into the
column is hard and the water coming out is soft.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 5 marks)
Page 13
Q11.
In some parts of the world the water is hard, but in other parts the water is soft.
(i)
Name an ion that causes water to be hard.
.....................................................................................................................................
(1)
(ii)
Describe how these ions get into the water.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(iii)
Sodium carbonate makes hard water soft.
Explain how.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 5 marks)
Q12.
(a)
In some parts of the world the water is hard, but in other parts the water is
soft.
Draw a ring around the correct answer to complete these sentences.
(i)
condense
Page 14
When water comes into contact with rocks, ions
dissolve
into the water.
evaporate
(1)
(ii)
calcium
Hardness in water is caused by
hydrogen
ions.
sodium
(1)
(iii)
sodium carbonate.
Hard water can be made soft by adding
sodium chloride.
sodium sulfate.
(1)
(iv)
The ions that cause hardness are removed by adding a substance
neutralises
which
oxidises
them.
precipitates
(1)
(b)
Hard water reduces the efficiency of kettles.
The picture shows a heating element from a kettle.
Page 15
Explain how hard water reduces the efficiency of kettles.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(c)
The diagram shows how pure water can be made from impure water by distillation.
Choose the correct words from the box to name apparatus X and Y.
beaker
condenser
flask
Page 16
thermometer
(i)
Apparatus X is a .............................................................................................. .
(1)
(ii)
Apparatus Y is a .............................................................................................. .
(1)
(Total 8 marks)
Q13.
Water is a natural resource. Drinking water in some parts of the UK is soft, but in
other parts drinking water is hard. Calcium ions in water cause water to be hard.
There are two types of hard water, permanent hard water and temporary hard water.
•
Permanent hard water can be caused by calcium sulfate (CaSO4) dissolved in the
water
•
Temporary hard water can be caused by calcium hydrogencarbonate (Ca(HCO3)2)
dissolved in the water
(a)
Temporary hard water causes the formation of scale on heating elements.
Photograph © Steve Gorton / Getty Images
(i)
Explain how scale forms on heating elements.
...............................................................................................................
...............................................................................................................
Page 17
...............................................................................................................
...............................................................................................................
(2)
(ii)
Suggest why scale on heating elements causes problems.
...............................................................................................................
...............................................................................................................
(1)
(b)
Permanent hard water can be softened.
(i)
Explain how adding sodium carbonate (Na2CO3) softens permanent hard
water.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(ii)
Explain how a water filter containing carbon, silver and ion exchange resin
softens permanent hard water.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(Total 7 marks)
Q14.
Water is a natural resource.
Page 18
(a)
Water in some parts of the UK is hard, but in other parts of the UK it is soft.
Draw a ring around the correct answer to complete each sentence.
condense
(i)
Water becomes hard because ions in rocks dissolve
into the water
evaporate
(1)
calcium
(ii)
Hardness in water is caused by hydrogen
ions
sodium
(1)
(b)
There are two types of hard water, permanent hard water and temporary hard
water.
Draw a straight line from each statement to the correct type of water.
Statement
Type of water
Permanent hard water
Easily makes a lather with soap
Temporary hard water
Can be made soft by boiling
Soft water
(2)
(c)
Water of the correct quality is essential for life.
In many parts of the world the water used for drinking contains solid particles and
harmful bacteria.
Suggest two methods that could be used to improve the quality of this water.
Page 19
1 .....................................................................................................................
2 .....................................................................................................................
(2)
(Total 6 marks)
Page 20
M1.
(a)
weak
not slightly
2
alkaline / base
mark independently
1
(b)
contains Ca2+ / Mg2+ / named calcium
compound / correct formula
do not accept reference to soap not calcium / magnesium
1
(c)
build up of fur / scale / forms CaCO3/ precipitate formed
not ‘scum’
wastes energy / less efficient / takes longer to boil
1
(d)
(i)
sample B
1
contains (calcium) sulphate / SO42–
1
not softened by boiling / does not contain many HCO3– ions / cannot
precipitate CaCO3
1
(ii)
by use of ion-exchange / washing soda / distillation
not detergent / soap
1
(e)
strengthen bones, teeth / taste
not good for you / healthier
1
[10]
Page 21
M2.
lower water heating costs
1
reduce soap used / no scum
not no blocked showers
1
less maintenance / use of plumber / don’t need to buy new heater or shower /
no descaling needed (pipes or showers) / no cleaning of blocked pipes
1
[3]
M3.
(a)
calcium
allow formulae
1
carbonate
1
(b)
(i)
soap
allow 2 marks for
“contains CaSO4 / Ca(HCO3)2 / Ca2+ / Mg2+”
1
forms scum / no bubbles / no lather
allow 1 mark for “contains Ca / Mg”
do not allow “contains CaCO3”
1
(ii)
taste / strengthen bones, teeth etc / health reason e.g. less heart
disease / makes better beer
1
(c)
(shake with) soap; makes scum / no lather
1
boil (a fresh sample)
1
retest with soap
1
Page 22
result/comparison
alternative answers:
boil (not to dryness)
cloudiness in water/some deposit formed
if a comparison is made with a sample of a soft water, a
further 2 marks would be possible
1
(d)
ion-exchange
1
[10]
M4.
(a)
perfume
1
(b)
a substance that whitens / removes colour or stains allow kills bacteria / germs
not ‘cleans’
1
(c)
(i)
does not form a lather (with soap)
accept ‘forms scum with soap’
or contains calcium sulphate / calcium hydrogen carbonate / soluble
magnesium salt / Ca2+ / Mg2+
1
(ii)
no scum formed / soap more effective / save money on soap / furs
up pipes etc / limescale deposits
not ‘to get lather’
1
(iii)
ion-exchange / add washing soda / distillation / boiling
1
Page 23
(d)
sulphuric acid
1
[6]
M5.
(a)
acidic
1
reacts
1
hard
1
tastes
1
(b)
(i)
scum / no lather / precipitate
1
(ii)
rain water is soft / pure / nothing dissolved / no limestone
not distilled
1
(iii)
lake water is hard / not soft / contains calcium compounds / dissolved
limestone
not impurities
1
(iv)
softened by boiling / loses hardness
1
temporary hardness removed / decomposition of calcium salts
1
[9]
M6.
(a)
water came into contact with rocks / ground / soil
ignore mountains
erode gets first mark
Page 24
1
ions or compounds or chemicals or they dissolved / soluble / leached / reacts /
forms a solution
do not accept gets picked up
accept water dissolves them from the rocks for 2 marks
1
(b)
(i)
calcium or magnesium
accept Ca2+ or Mg2+ or Ca or Mg
do not accept Ca+ alone
1
(ii)
answers must involve both calcium and magnesium
totals required for 2 marks
Ridgway: Ca + Mg = 53
1
Homeland: Ca + Mg = 27
accept there is (almost) twice as much
Magnesium and Calcium in Ridgway water for 1 mark
1
(iii)
equal volumes / quantities / amounts of water
1
add soap with / shaking / mixing / agitation
same amounts of soap = max 2
do not accept just add
do not accept solid soap
1
the harder sample (Ridgway) needs 2 × more soap to give lather
or the less hard sample (Homeland) needs half as much
soap to give lather can get twice as much scum with harder
(Ridgway) sample
1
[8]
Page 25
M7.
two methods and 1 linked explanation or 1 method and two explanations, 1 linked =
3 marks
no linking of method and explanation then max 2 marks
ignore references to removal of hardness
method 1:
filter
ignore screening / sedimentation
explanation 1:
remove insoluble substances / remove solids / small bits / dirt / mud/ soil / sand / silt
method 2:
precipitate / flocculate / add eg. alum
allow other named substances
explanation 2:
removes (some) soluble material as solids / removes (some) metal ions
method 3:
add chlorine / chlorine dioxide / ozone
explanation 3:
sterilise / kill bacteria / microorganisms / microbes
ignore ‘remove bacteria’
ignore disinfect
[3]
M8.
(a)
contains (large amounts of) dissolved solids / difficult to remove dissolved
solids
allow salty / too much salt
allow sea water makes you thirsty / vomit
allow polluted / untreated / contaminated
Page 26
1
(b)
filtered: removes solids / removes insoluble material / dirt
ignore large objects
1
chlorine: kills/destroy bacteria/microbes/ germs etc
allow disinfect / sterilise or gets rid of bacteria
ignore purify / clean
1
[3]
(a)
scale – (solid) formed when heat decomposes dissolved calcium / magnesium
compounds owtte
allow: scale is formed when hard water is heated / boiled (to
leave magnesium / calcium compounds)
M9.
scale is calcium carbonate / CaCO3 or magnesium carbonate / MgCO3
ignore evaporate
1
scum – (ppt) formed when soap reacts with calcium / magnesium (ions) owtte
allow scum is formed when hard water reacts with soap
scum is calcium stearate / magnesium stearate
1
(b)
calcium (ions) / Ca2+ / magnesium (ions) / Mg2+
1
replaced by hydrogen ions / H+ / sodium ions / Na+
1
[4]
M10.
(a)
calcium
Ca / Ca2+
allow Ca+
or
Page 27
magnesium
Mg / Mg2+
allow Mg+
1
(b)
sodium
allow Na / Na+
1
(c)
hard water before: scum / precipitate / solid
1
soft water after: lather / bubbles
1
equal volumes of water or soap
allow same temperature
allow same soap
allow shake
1
[5]
M11.
(i)
calcium (ion) / Ca2+
ignore any formula
if ion only must be correct
accept magnesium (ion) / Mg2+
do not accept named compounds
1
(ii)
contact with rocks
accept named rocks
ignore ground / deposits / soil / minerals / ores
1
(ions / substances) dissolved / soluble / leached / reacts
ignore erode / corrode / picks up / absorb
1
(iii)
(ions / substances / they) react / replace / remove
Page 28
accept displace
1
forms precipitate / insoluble / solid
if ion exchange (column) = max 1 mark
1
[5]
M12.
(a)
(i)
dissolve
1
(ii)
calcium
1
(iii)
sodium carbonate
1
(iv)
precipitates
1
(b)
any two from:
•
(lime)scale
accept precipitate
ignore scum
•
acts as insulator / covers element / prevents heat passing through
•
requires more energy
ignore references to time
2
(c)
(i)
flask
accept clear misspellings
1
(ii)
condenser
accept clear mispellings
1
[8]
Page 29
M13.
(a)
(i)
on heating, the calcium hydrogencarbonate decomposes
1
forming a scale of insoluble calcium carbonate
1
(ii)
the scale reduces the efficiency of the heating element
or the scale increases energy costs / uses more energy
1
(b)
(i)
the sodium carbonate / carbonate ions react with calcium /
magnesium ions, forming a precipitate of calcium
carbonate / magnesium carbonate
1
therefore the water is softened because this removes the
calcium / magnesium ions, which cause hardness, from
the water
1
(ii)
sodium / hydrogen ions are present in the ion exchange resin
1
therefore the water is softened because these ions take
the place of calcium / magnesium ions that cause
hardness in the water
1
[7]
M14.
(a)
(i)
dissolve
1
(ii)
calcium
1
(b)
(i)
easily makes lather with soap – soft water
1
made soft by boiling – temporary hard water
Page 30
1
(c)
filter
1
add chlorine
accept sterilise
1
[6]
Page 31