C2 2.1a – Student practical sheet
Identifying simple molecular substances 1
You are going to test some substances to try and work out if they have a simple molecular
structure. None of the substances are metals.
Aim
To successfully identify simple molecular substances.
Equipment
●
eye protection
●
peg to hold ignition tubes
●
Bunsen burner
●
samples to test
●
heatproof mat
●
spatula
●
ignition tubes
Safety
●
Wear your eye protection.
●
Place hot ignition tubes on your heatproof mat.
●
Stop heating once a substance has melted.
What you need to do
1
Place a small amount of one substance into an ignition
tube.
2
Heat the sample in the ignition tube in a hot Bunsen
flame for a minute or so.
3
Look to see if the substance melts easily.
4
Try the other samples each in a different ignition tube.
5
Present your results in a suitable table that indicates
whether the melting and boiling points are high or low.
Using the evidence
1
Decide which of the substances have a simple molecular structure. (1 mark)
2
Explain how you can tell which substances have a simple molecular structure. (1 mark)
Evaluation
3
How could you tell if the melting point was high or low? (1 mark)
4
Why was it important that you were told that no substances were metals? (1 mark)
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153
C2 2.1b – Student worksheet
Identifying simple molecular substances 2
The table shows some data about six different substances.
Substance
Melting point
(°C)
Boiling point
(°C)
A
114
B
Electrical conductivity
as solid
Electrical conductivity
as liquid
184
Does not conduct
Does not conduct
234
327
Does not conduct
Does not conduct
C
–39
357
Conducts
Conducts
D
685
1324
Does not conduct
Conducts
E
1713
2230
Does not conduct
Does not conduct
F
–182
–161
Does not conduct
Does not conduct
1
Decide which substances have a simple molecular structure. (3 marks)
2
a
What are the key properties of simple molecular substances? (2 marks)
b
Explain why simple molecular substances have these properties. (2 marks)
C2 2.1c – Student worksheet
Different types of structures
Complete the table about substances with each of the types of structures shown as you work
through this topic.
Type of structure
Simple molecular
Ionic
Giant covalent
Metallic
Description of
the structure
Type of bonding
Melting and
boiling points
(with reason)
Electrical
conductivity
(with reason)
Which types of
substances have
this structure
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C2 2.1d – Student worksheet
Using simple molecular substances
Ethyl ethanoate is a simple molecular substance. The boiling point of ethyl ethanoate is 77 °C. It is
used as the solvent in some nail varnish because it evaporates very easily. A diagram of a
molecule of ethyl ethanoate is shown in Figure 1.
Figure 1: Ethyl ethanoate
Sulfur hexafluoride is a simple molecular substance. The boiling point
of sulfur hexafluoride is –62 °C. It is used as the gas inside some
electrical devices such as circuit breakers. It is used in electrical
devices because it does not conduct electricity. A diagram of a
molecule of sulfur hexafluoride is shown in Figure 2.
Figure 2: Sulfur hexafluoride
1
Give the molecular formula of ethyl ethanoate. (1 mark)
2
Give the molecular formula of sulfur hexafluoride. (1 mark)
3
There are sticks between the atoms in the molecules. What do these represent? (1 mark)
4
Explain why ethyl ethanoate is used in nail varnish. (1 mark)
5
Explain why ethyl ethanoate has a low boiling point and so evaporates easily? (2 marks)
6
Explain why sulfur hexafluoride is used in circuit breakers. (1 mark)
7
Explain why sulfur hexafluoride does not conduct electricity. (1 mark)
8
Which of the substances in the table have a simple molecular structure? (1 mark)
Substance
Melting point
(°C)
Boiling point
(°C)
Electrical conductivity
as solid
Electrical conductivity
as liquid
P
56
137
Does not conduct
Does not conduct
Q
835
1535
Does not conduct
Conducts
R
98
432
Conducts
Conducts
S
–78
95
Does not conduct
Conducts
T
1218
1946
Does not conduct
Conducts
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155
C2 2.2a – Student practical sheet
Identifying ionic substances 1
You are going to test some substances to try and work out if they have an ionic structure. You may
not be able to tell for some.
Aim
To successfully identify ionic substances.
Equipment
●
eye protection
●
electrode holder
●
power pack/batteries
●
boiling tube
●
2 × graphite electrodes
●
samples to test
●
boiling tube rack
●
heatproof mat
●
small beaker
●
bung
●
ignition tubes
●
spatula
●
Bunsen burner
●
light bulb
●
wires
●
crocodile clips
●
peg to hold ignition tubes
Safety
●
Wear eye protection.
●
Place hot ignition tubes on your heatproof mat.
●
Stop heating once a substance has melted.
●
When shaking the boiling tube, keep your thumb on the bung.
●
When testing to see if solutions conduct electricity, only keep the circuit connected for a few
seconds. It may produce toxic fumes otherwise.
What you need to do
1
Prepare a results table for your results like the one shown.
Substance
Soluble in
water? (/)
Solution
conducts
electricity?
(//insoluble)
Is the substance ionic?
Not ionic ()
Cannot tell ()
Is ionic ()
2
Place a spatula load of the first substance into a boiling tube. It does not matter which order
you do the substances in.
3
Add water so the tube is about one third full.
4
Place a bung in the tube.
5
Shake to see if the solid dissolves.
6
Complete the table to show if the substance dissolves.
7
If the substance dissolves, pour it into a smaller beaker.
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C2 2.2a – Student practical sheet
8
Set up the circuit as shown in the diagram and test if the solution conducts electricity by seeing
if the light bulb lights up. You only need to have the circuit connected for a few seconds to see
if it conducts electricity.
9
Complete the table to show if the dissolved substance conducts electricity.
10 Clean the apparatus and try the next substance until you have tested them all.
Using the evidence
1
Decide which of the substances are ionic. (1 mark)
2
Which substances might be ionic but you cannot tell? (1 mark)
3
Explain how you can tell which substances are ionic. (2 marks)
4
For the substances where you cannot tell whether they are ionic, explain why you cannot tell.
(1 mark)
Evaluation
5
How could you tell if the melting point was high or low? (1 mark)
6
For the substances where you cannot tell whether they are ionic, describe tests that you could
do to find out if they are ionic. (1 mark)
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157
C2 2.2b – Student worksheet
Identifying ionic substances 2
The table shows data for six different substances.
Substance
Melting point
(°C)
Boiling point
(°C)
Electrical conductivity as
Solid
Liquid
Solution (aq)
P
650
1107
Conducts
Conducts
Insoluble
Q
114
184
Does not
conduct
Does not
conduct
Does not
conduct
R
801
1467
Does not
conduct
Conducts
Conducts
S
2040
2980
Does not
conduct
Conducts
Insoluble
T
119
445
Does not
conduct
Does not
conduct
Insoluble
U
1610
2230
Does not
conduct
Does not
conduct
Insoluble
1
Decide which substances have an ionic structure. (2 marks)
2
a
What are the key properties of ionic substances? (2 marks)
b
Explain why ionic substances have these properties. (2 marks)
C2 2.2b – Student worksheet
Identifying ionic substances 2
The table shows data for six different substances.
Substance
Melting point
(°C)
Boiling point
(°C)
Electrical conductivity as
Solid
Liquid
Solution (aq)
P
650
1107
Conducts
Conducts
Insoluble
Q
114
184
Does not
conduct
Does not
conduct
Does not
conduct
R
801
1467
Does not
conduct
Conducts
Conducts
S
2040
2980
Does not
conduct
Conducts
Insoluble
T
119
445
Does not
conduct
Does not
conduct
Insoluble
U
1610
2230
Does not
conduct
Does not
conduct
Insoluble
1
Decide which substances have an ionic structure. (2 marks)
2
a
What are the key properties of ionic substances? (2 marks)
b
Explain why ionic substances have these properties. (2 marks)
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C2 2.2c – Student worksheet
Using ionic substances
Kilns are hot ovens with many uses, for example
drying wood and making ceramics from clay. For
some uses, the temperature inside the kiln can
reach over 1000 °C. It is important that the inside of
the kiln does not melt. Aluminium oxide is used to
coat the inside of some kilns. Aluminium oxide is an
ionic compound with a melting point of 2054 °C.
Silver is a very expensive metal. Instead of making
objects such as cutlery and trophies out of solid
silver, they can be made of another metal and
coated with a layer of silver. This is called silver
plating. The object being plated with silver is placed
into an electrical circuit as the negative electrode in
a solution of an ionic compound such as silver
nitrate, along with a piece of silver as the positive
electrode. The solution of silver nitrate conducts
electricity and the metal is coated with silver.
Cutlery can be plated with silver through the electrolysis of the ionic compound silver nitrate.
1
3+
2–
a
Give the formula of aluminium oxide (aluminium ions = Al , oxide ions = O ). (1 mark)
b
Give the formula of silver nitrate (silver ions = Ag , nitrate ions = NO3 ). (1 mark)
–
+
2
Explain why aluminium oxide is used in the lining of kilns. (1 mark)
3
Explain why aluminium oxide has a high melting point. (1 mark)
4
Silver nitrate solution can be used in electroplating because it conducts electricity. Explain why
silver nitrate solution conducts electricity. (1 mark)
5
Neither aluminium oxide nor silver nitrate conducts electricity as a solid. Explain why. (1 mark)
6
Which of the substances in the table are ionic? (1 mark)
Substance
Melting point (°C)
Boiling point (°C)
Electrical conductivity as
Solid
Liquid
A
80
176
Does not conduct
Does not conduct
B
845
1428
Conducts
Conducts
C
756
1269
Does not conduct
Conducts
D
1841
2249
Does not conduct
Conducts
E
–74
38
Does not conduct
Does not conduct
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159
C2 2.3a – Student practical sheet
Testing giant covalent substances
A few substances, including silicon dioxide and graphite, have a giant covalent structure.
Aim
To investigate the properties of giant covalent substances.
Equipment
●
Bunsen burner
●
power pack/batteries
●
crocodile clips
●
spatula
●
eye protection
●
wires
●
heatproof mat
●
●
light bulb
●
peg to hold ignition
tubes
samples to test: silicon
dioxide powder, pieces of
silica (for testing electrical
conductivity), graphite
powder, graphite rods (for
testing electrical conductivity)
Safety
●
Wear eye protection.
●
Place hot tubes on the heatproof mat and remember that
they stay hot for a long time.
What you need to do
Carry out the following tests for both silicon dioxide and graphite.
Place a small amount of silicon dioxide powder or graphite powder into an ignition tube.
Heat the sample in the ignition tube in a hot Bunsen flame for a minute or so.
Look to see if the substance melts easily. Present your results in a suitable table.
Test the electrical conductivity of each substance using the graphite rods and a piece of silicon
dioxide. Test using a circuit including a light bulb.
Using the evidence
1
2
a
Describe the melting points of giant covalent substances. (1 mark)
b
Explain why giant covalent substances have melting points like this. (2 marks)
a
Describe the electrical conductivity of giant covalent substances. (2 marks)
b
Explain why giant covalent substances have electrical conductivity like this. (2 marks)
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C2 2.3b – Student worksheet
Diamond and graphite
Diamond and graphite are both forms of carbon that have giant covalent structures. They have
both been used for hundreds of years.
Complete the table using the suggested words and phrases. When you have finished, the table
should summarise the properties of diamond and graphite.
Properties
Reason
●
very high
●
●
soft and slippery
lots of strong covalent bonds have to be
broken
●
conducts heat and electricity
●
●
lots of strong covalent bonds have to be
broken
very hard
●
●
there are some delocalised electrons
does not conduct heat and electricity
●
●
there are no delocalised electrons
very high
●
●
three
the atoms are bonded together in a rigid
network
●
four
●
layers of atoms can slide over each other
Graphite
Diamond
Property:
Property:
Reason:
Reason:
Property:
Property:
Reason:
Reason:
Property:
Property:
Reason:
Reason:
Structure
Number of covalent
bonds each carbon atom
forms
Melting point
Hardness
Electrical and thermal
conductivity
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161
C2 2.3c – Student worksheet
Silicon dioxide
Almost 75% of the Earth’s crust is made up of silicon and oxygen atoms. Many of these atoms are
combined together to make silicon dioxide (silica).
Silicon dioxide has a giant covalent structure. It has the formula SiO2. The melting point of silicon
dioxide is 1610 °C. It is very hard and it does not conduct heat or electricity.
1
Explain why silicon dioxide:
a
has a very high melting point. (2 marks)
b
is hard. (1 mark)
c
does not conduct electricity. (1 mark)
2
Each line in the diagram represents a covalent bond. What is a covalent bond? (1 mark)
3
a
In which group of the periodic table is oxygen? (1 mark)
b
How many electrons does oxygen have in its outer energy level (shell)? (1 mark)
c
How many more electrons does oxygen need to fill its outer energy level (shell)? (1 mark)
d
How many covalent bonds does oxygen need to make to fill its outer energy level (shell)?
(1 mark)
e
Look at the oxygen atoms in the centre of the structure. How many bonds does each
oxygen atom make? (1 mark)
a
In which group of the periodic table is silicon? (1 mark)
b
How many electrons does silicon have in its outer energy level (shell)? (1 mark)
c
How many more electrons does silicon need to fill its outer energy level (shell)? (1 mark)
d
How many covalent bonds does silicon need to make to fill its outer energy level (shell)?
(1 mark)
e
Look at the silicon atoms in the centre of the structure. How many bonds does each silicon
atom make? (1 mark)
4
5
The formula of silicon dioxide is SiO2. Explain what this formula means. (1 mark)
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C2 2.3d – Student worksheet
Buckyballs and buckytubes
Diamond and graphite are two forms of carbon that have been known for many
years. In 1996, Professor Sir Harry Kroto won the Nobel Prize for Chemistry for
his discovery of a third form of carbon. It was made by the action of a laser on
some graphite. It was called buckminsterfullerene after the American architect
Buckminster Fuller, who built buildings in complex geometric shapes.
Buckminsterfullerene has the same shape as a football.
Several other ball-shaped molecules of carbon have been made, including C70,
C76 and C84. All these carbon molecules are fullerenes and commonly known as
buckyballs. It has been discovered that tiny quantities
of these molecules occur in soot.
Many scientists are researching to find uses of
buckyballs; some potential uses include applications in
medicine or as lubricants. However, so far the uses of
buckyballs are limited.
Related fullerenes have been made that have a tube shape and are known as buckytubes. Some
of these are molecules with a fixed number of atoms and closed ends. Some are open-ended and
vary in length. They are effectively graphite sheets rolled into tubes.
Buckytubes have some remarkable properties. They are good
electrical conductors owing to delocalised electrons that can
move along the tube. They are also very strong and can be
used to make stronger but lighter materials. Buckytubes are
very resistant to heat because they have very high melting
points.
Buckytubes are much more useful than buckyballs and already have several uses, for example for
drug delivery into the body, in lubricants, as catalysts, and in nanotubes for reinforcing materials
such as tennis rackets.
1
Which two forms of carbon have been known for many years? (1 mark)
2
a
What is buckminsterfullerene? (1 mark)
b
How was it made? (1 mark)
c
Explain why buckminsterfullerene has a simple molecular and not a giant covalent
structure. (1 mark)
a
What are buckyballs? (1 mark)
b
What are buckytubes? (1 mark)
c
Which are more useful, buckyballs or buckytubes? (1 mark)
a
Give some special properties of buckytubes. (3 marks)
b
Give a use of buckytubes. (1 mark)
3
4
5
Buckytubes are often open-ended and do not have a fixed length. Do these buckytubes have a
simple molecular or a giant covalent structure? Explain your answer. (2 marks)
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163
C2 2.4a – Student practical sheet
Using shape memory alloys
Nitinol is a shape memory alloy. This is an alloy that will return to its original shape when heated. In
this experiment you will use springs made of nitinol.
Aim
To show that springs made of nitinol return to their original shape when heated.
Equipment
●
beakers
●
smart springs
●
kettle to supply hot water
●
tweezers
Safety
●
The hot water from the kettle needs to be over 70 °C, so the spring will be very hot.
What you need to do
Practical
1
Place some hot water from a kettle in a beaker.
2
Stretch a nitinol spring and place it in the beaker. If the water is hot enough, it will return to its
original shape.
3
Remove the spring with tweezers.
4
Stretch the spring and try this again.
Demonstration
1
Your teacher will set up the apparatus as shown
using a power supply, nitinol spring and mass.
2
Your teacher will turn on the power so you can see
how it affects the nitinol spring.
3
Your teacher will turn off the circuit and let the
spring cool until the mass drops back down. Then
your teacher will turn the circuit on again.
Using the evidence
1
Describe what happens to the nitinol spring when placed in hot water. (1 mark)
2
Describe what happens to the nitinol spring when it is heated by passing an electric current
through it. (1 mark)
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C2 2.4b – Student practical sheet
Making an alloy
In this experiment you are going to make an alloy of lead and compare it with pure lead.
Aim
To make an alloy of lead and compare it with pure lead.
Equipment
●
Bunsen burner
●
spatula
●
carbon powder
●
tongs
●
crucible
●
tray of casting sand
●
eye protection
●
●
heatproof mat
thermal protective
gloves
●
lead
●
tin
●
pipe clay triangle
●
tripod
Safety
●
Wear eye protection.
●
Be very careful with the hot apparatus and the molten metal.
●
Lead is toxic. Avoid breathing the vapour from the experiment.
●
Wash hands after handling lead, tin and the cooled alloy.
What you need to do
1
Collect a tray of casting sand. Make an indent in the sand using your finger.
2
Weigh out 1 g of lead and 1 g of tin.
3
Put the lead into the crucible.
4
Put the crucible into a pipe clay triangle on a tripod on a mat.
5
Heat the crucible until the lead melts. Place a spatula load of carbon on top of the molten lead
to stop it forming a skin.
6
Add the tin to the molten lead and stir with the spatula until the tin has melted and the two
metals are thoroughly mixed.
7
Put on heat protection gloves. Pick up the crucible with tongs and pour the mixture into the
indent in the sand. Take great care to not spill or splash any of the hot, molten mixture.
8
Leave the alloy for a few minutes to cool down.
9
Collect a piece of lead and try scratching the lead and alloy together. The one that does not
scratch is the hardest.
Using the evidence
1
Record whether the lead or the alloy was harder. (1 mark)
2
Explain why the lead or the alloy was harder. (2 marks)
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165
C2 2.4c – Student worksheet
Using different alloys
Pure iron is too soft to be useful. Steels are alloys of iron. They are made by
mixing iron with other elements. Different steels have different properties and so
different uses.
Type of steel (or iron)
What it contains
Properties
Pure iron
Iron
Soft and weak
Low carbon steel
Iron + about 0.1% carbon
Harder and stronger than iron
High carbon steel
Iron + about 1% carbon
Harder and stronger than low
carbon steel but brittle
Stainless steel
Iron + 18% chromium + 10% nickel
Very resistant to corrosion
Titanium steel
Iron + titanium
Able to withstand very high
temperatures
Manganese steel
Iron + 14% manganese
Very hard
Use the information in the table to choose the best steel for each of the following.
Give reasons for your answer.
1
paper clips (1 mark)
5
kitchen sinks (1 mark)
2
cutlery (1 mark)
6
spacecraft (1 mark)
3
nails for hammering into bricks (1 mark)
7
tools for breaking up hard rocks (1 mark)
4
engine parts for very high temperatures
(1 mark)
8
razor blades (1 mark)
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C2 2.4d – Student worksheet
Alloys of gold
Jewellery is not made from pure gold because
it is too soft. Gold jewellery is made from alloys
where the gold is mixed with other metals.
Different alloys have different colours. The
most common form of gold has a yellow
colour, whereas white gold looks more like
silver and rose gold has a rose pink appearance.
The purity of the gold is measured in carats or by the fineness.
Pure gold has 24 carats and a fineness of 1000.
The table shows different alloys of gold to make jewellery.
Type of
gold
Carat
Fineness
% Gold
% Silver
% Copper
% Zinc
22-carat
22
917
91.7
5.5
2.8
18-carat
yellow
18
750
75
16
9
18-carat
rose
18
750
75
4
21
18-carat
white
18
750
75
4
4
9-carat
yellow
9
375
37.5
10
45
7.5
9-carat
white
9
37.8
37.5
0
40
10.4
% Palladium
% Nickel
17
11.8
1
What is an alloy? (1 mark)
2
a
Why is gold jewellery made out of gold alloys and not pure gold? (1 mark)
b
Explain this difference in properties by a discussion of the alloys compared with pure gold.
(2 marks)
3
Use the data in the table to explain why 18-carat gold can have different colours. (1 mark)
4
Some jewellery is 14-carat gold.
5
6
a
What percentage of gold is in this alloy? (1 mark)
b
What is the fineness of this gold? (1 mark)
An alloy of gold contains 60% gold.
a
What is the carat of this gold? (1 mark)
b
What is the fineness of this gold? (1 mark)
How do you think the price of 9-carat gold compares to that of 18-carat gold? Explain your
answer. (2 marks)
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167
C2 2.4e – Student worksheet
What type of structure?
1
Decide whether the substances in the table have a simple molecular, giant covalent, ionic or
metallic structure. (1 mark per substance, total 10 marks)
Substance
2
3
Melting point
(°C)
Boiling point
(°C)
Electrical conductivity as
Solid
Liquid
Solution (aq)
A
963
1560
Does not
conduct
Conducts
Conducts
B
1063
2967
Conducts
Conducts
Insoluble
C
123
187
Does not
conduct
Does not
conduct
Insoluble
D
–7
59
Does not
conduct
Does not
conduct
Does not
conduct
E
3527
4027
Does not
conduct
Does not
conduct
Insoluble
F
30
2397
Conducts
Conducts
Insoluble
G
1713
2230
Does not
conduct
Does not
conduct
Insoluble
H
–138
0
Does not
conduct
Does not
conduct
Insoluble
I
–189
–188
Does not
conduct
Does not
conduct
Insoluble
J
1100
1501
Does not
conduct
Conducts
Insoluble
Explain why:
a
ionic substances have high melting points. (1 mark)
b
simple molecular substances have low melting points (1 mark)
c
giant covalent substances have very high melting points (1 mark)
d
metallic substances have high melting points (1 mark)
Explain why:
a
ionic substances conduct electricity when molten or dissolved but not when solid (1 mark)
b
simple molecular substances do not conduct electricity (1 mark)
c
giant covalent substances do not conduct electricity, but graphite does (1 mark)
d
metallic substances conduct electricity (1 mark)
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C2 2.5a – Student practical sheet
Testing polymers
In this experiment, you are going to test some polymers to see if they are thermosoftening or
thermosetting polymers.
Aim
To correctly work out if polymers are thermosoftening or thermosetting.
Equipment
●
eye protection
●
nail in a rubber bung
●
Bunsen burner
●
samples of polymers
●
heatproof mat
Safety
●
Wear your eye protection.
●
Hold the rubber bung and not the nail itself.
●
Place all hot samples and the hot nail on the heatproof mat.
●
Do not heat the polymer samples in the Bunsen flame.
What you need to do
1
Place a polymer sample on the heatproof mat.
2
Holding the rubber bung, heat the end of the nail in a hot Bunsen flame for about 20 seconds.
3
Holding the runner bung, press the hot end of the nail on the polymer on the heatproof mat.
Look to see if the polymer softens or melts.
4
Record the result in a suitable table. Indicate in your table if the polymer is thermosoftening or
thermosetting.
5
Test the next sample in the same way.
Using the evidence
1
2
a
List the thermosoftening polymers. (1 mark)
b
Explain why they soften on heating. (1 mark)
a
List the thermosetting polymers. (1 mark)
b
Explain why they do not soften on heating. (1 mark)
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169
C2 2.5b – Student practical sheet
Making slime
Slime can be made by the reaction of poly(ethenol) with borax. Slime is very viscous. Viscous
liquids do not flow easily. In this experiment, you are going to make some slime and see how
changing the reaction conditions affects the viscosity of the slime.
Aim
To make slime under different conditions and compare the viscosity.
Equipment
●
eye protection
●
2% borax solution
●
plastic cups
●
4% borax solution
●
4% poly(ethenol) solution
●
10 cm measuring cylinder
●
stirring rod
●
25 cm measuring cylinder
●
stopwatch
●
newspaper
3
3
Safety
●
Wear your eye protection.
●
Wash your hands after the experiment.
What you need to do
1
Throughout your experiment work on newspaper.
2
Place 25 cm of 4% poly(ethenol) in a yoghurt pot or plastic cup using a measuring cylinder.
3
Place 5 cm of 4% borax solution into the beaker.
4
Stir well with a stirring rod for a few minutes.
5
Pour the slime from one cup to another, timing how long it takes. You should do this a few
times and work out an average time.
6
Record your results in a suitable table.
7
Repeat the experiment but use 2% borax solution.
8
At the end, wrap up all the cups and slime in the newspaper and put in the bin.
3
3
Using the evidence
1
Which slime was most viscous? (1 mark)
2
What was changed in the experiment that affected the properties of the slime? (1 mark)
Evaluation
3
How easy was it to time how long it took for the slime to flow from one cup to the other?
(1 mark)
4
Is this method reliable? Explain your answer. (1 mark)
Extension
5
Explain in terms of structure and bonding why the viscosity changes as it does. (2 marks)
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C2 2.5c – Student worksheet
Investigating slime
Slime can be made by reacting poly(ethenol) with borax. The slime
is very viscous so when it is poured through a funnel, it takes some
time for it all to fall through. The time it takes to fall through the
funnel can be used as a measure of the viscosity of the slime. The
more viscous the slime, the longer it takes to fall through the funnel.
A student wanted to see how changing the amount of borax added
to the poly(ethenol) affects the viscosity. She changed the amount
of borax added by changing the concentration of the borax solution.
She measured the viscosity by timing how long it took the borax to
3
move through the funnel. In each experiment, she reacted 25 cm
3
of 4% poly(ethenol) solution with 5 cm of borax solution.
Her results are shown in the table.
Concentration of borax solution
used to make slime
Time taken for slime to move through funnel(s)
Test 1
Test 2
Test 3
1%
2
3
2
2%
8
9
7
3%
17
18
21
4%
46
30
49
5%
98
110
105
1
a
What is the independent variable in this experiment? (1 mark)
b
What range was used for this variable? (1 mark)
Mean
2
The dependent variable is the time the slime takes to move through the funnel. Is this a
categoric, discrete or continuous variable? (1 mark)
3
In order to make it a fair test, the student controlled some key variables.
a
Identify two of these key variables. (2 marks)
b
Why were these variables controlled? (1 mark)
4
The student carried out each test three times. Repeating experiments can make the calculated
mean more reliable. Explain why. (2 marks)
5
a
There seems to be one anomalous result in the table. Identify this result. (1 mark)
b
Suggest a possible reason for this anomalous result. (1 mark)
c
Copy and complete the table by calculating the mean time for each slime to move through
the funnel. (2 marks)
6
Plot a suitable chart or graph of these results. (4 marks)
7
Use the results and chart/graph to describe the relationship between the concentration of borax
used and the time it takes for the slime to pass through the funnel. (2 marks)
8
Use the results and chart/graph to describe the relationship between the concentration of borax
used and the viscosity of the slime. (2 marks)
9
The student wanted to do another investigation to see how changing the temperature affects
the viscosity of the slime. Why would it not be sensible to use slime made from 1% borax for
this experiment? (1 mark)
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171
C2 2.5d – Student worksheet
Using thermosoftening and thermosetting
polymers
Thermosoftening polymers soften and then melt on heating. This is because the polymer chains
are not joined together. This means that they can be recycled by being melted and remoulded.
Thermosetting polymers do not soften on heating. This is because the polymer chains are held
together by covalent bonds. This means that they cannot be recycled by being melted and
remoulded.
Polythene is an example of a thermosoftening polymer. It is used to make plastic bags. Another
example of a thermosoftening polymer is PET, which is used to make plastic bottles.
Superglue is an example of a thermosetting polymer. The monomer polymerises when it is
exposed to moisture in the air. Kitchen worktops are often made of melamine, another
thermosetting polymer.
Natural rubber is a thermosoftening polymer. Charles Goodyear discovered that by heating natural
rubber with sulfur, a polymer formed that had different properties from natural rubber. He called this
vulcanised rubber and it is a thermosetting polymer. This form of rubber is used in car tyres.
1
Explain why and how PET bottles and polythene bags can be recycled. (2 marks)
2
Explain why superglue does not soften on heating and so continues to hold objects together in
heat. (1 mark)
3
Why is it important that kitchen worktops are made of thermosetting polymers? (1 mark)
4
Why is vulcanised rubber suitable for making car tyres but natural rubber is not? (2 marks)
5
Suggest a household item that needs to be made from a thermosetting polymer to withstand
high temperatures without softening or melting. (1 mark)
6
Why do thermosoftening polymers soften and melt on heating but thermosetting polymers do
not? (2 marks)
7
Circuit boards are often made from polymers called polyimides. Circuit boards can get hot. Are
polyimides thermosoftening or thermosetting polymers? (1 mark)
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C2 2.6a – Student worksheet
Metres and nanometres
Cut out the cards and match up the sizes with the pictures. Arrange the sets in
order of size from the biggest to the smallest.
1/10 000 000th m
1/1 000 000 000th m
(1 nanometre)
1 metre
1/1 000 000th m
1/10 000th m
1/10th m
marbles
virus
salt crystals
large molecules
child
1m
1 × 10 m
-2
1 × 10 m
plant cell or large
bacterium
-3
1 × 10 m (1 mm)
-7
1 × 10 m
1 × 10 m (1 cm)
(1 micrometre)
1/1000th m
(1 millimetre)
1/100 000 000th m
small bacterium
1/100 000th m
1/100th m
(1 centimetre)
atoms and small
molecules
thickness of human
DVD
hair
-4
1 × 10 m (1 μm)
-8
1 × 10 m
-6
-9
1 × 10 m (1 nm)
-1
-5
1 × 10 m
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173
C2 2.6b – Student worksheet
Are nanoparticles safe?
The Royal Society and the Royal Academies of Engineering published a report on nanotechnology
in 2004. The following text is a summary of the recommendations from the Royal Society website.
Most current and future nanotechnologies, such as computer chips and catalysts, pose no new
health or safety risks. This is because the nanomaterial is fixed or etched onto a larger object and
therefore unable to stray into the environment.
But concerns do exist about the possible impacts of manufactured nanoparticles and nanotubes
that are free to move around rather than being fixed or embedded into a bulk material. Although
these represent just a tiny fraction of all nanotechnologies, there is some evidence that their small
size may increase any potential toxicity. Certainly, the toxicity of a material in larger form doesn’t
tell us what its toxicity will be when it is nanosized.
The worry is that free nanoparticles could be inhaled, ingested or enter the body via the skin, and
then cause damage to cells. Nanotubes, for example, are structurally similar to asbestos fibres,
which can cause respiratory problems when inhaled in large amounts over long periods.
The Royal Society and Royal Academy of Engineering Report calls for:
●
free nanoparticles to be treated and labelled as new chemicals
●
research into potential hazards to keep pace with new developments
●
the UK government to provide funds for a new research centre to address safety concerns.
Currently, there is only very limited knowledge about the effects of inhaling nanoparticles or
nanotubes, but it’s thought that any risk would be linked to large doses. This means that any
hazard applies mainly to workers and researchers involved in their manufacture. The Health and
Safety Executive (HSE) already has interim guidelines in place on the use of nanoparticles in the
workplace, so the report calls for:
●
the HSE to review existing regulations and consider setting lower exposure levels for
manufactured nanoparticles
●
workplace exposure to be carefully monitored.
It is thought that the nanoparticles in sunscreens and cosmetics cannot penetrate the skin, but
further studies are needed to confirm this. So the report recommends that:
●
industry publishes the manner in which their safety tests have taken the special properties of
nanoparticles into account
●
consumer products containing manufactured nanoparticles should be approved by an
independent safety committee before hitting the shelves.
At present, almost nothing is known about the potential effects of free nanoparticles and nanotubes
on the environment. But it’s possible that they could enter the food chain, and affect plants and
animals. So the report recommends that:
●
their release be minimised until their effects are better understood.
Some are concerned about grey goo, a fictitious notion in which self-replicating, man-made, nanorobots devour the Earth and turn it into a grey goo. But there is no evidence to suggest that
nanobots like this could be made. The originator of the grey goo scenario, Dr Eric Drexler, has
even retracted his original proposition.
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C2 2.6c – Student worksheet
Carbon nanotubes in the fight against cancer
There are over 200 different types of cancer. Each one has different causes and needs different
treatments. All cancers involve the body’s cells growing out of control. They multiply very quickly
and form a tumour. Cancer cells may spread around the body causing more tumours.
Advances in medicine mean that many cancers can be treated if they are detected early enough
and the cancer cells killed. Chemotherapy and radiotherapy are used to treat many cancers.
However, both of these involve killing healthy cells as well as cancer cells. Nanoparticles have
recently been used to kill cancer cells without killing healthy cells. Nanoparticles are particles
between 1 nm and 100 nm in size.
In summer 2005, scientists at Stanford University in the USA
published a paper in a scientific journal. They reported that
they had put carbon nanotubes inside cancer cells. In order to
get the nanotubes into the cancer cells, they had been coated
with a vitamin called folate. Cancer cells are covered with
receptors for folate but normal cells are not. This meant that
the nanotubes did not go into the healthy cells. They shone
infrared light from a laser onto the cells, which made the
nanotubes heat up to about 70 °C, and this killed the cells.
When the scientific paper was published, the researchers had only tried this treatment on cancer
cells grown in the laboratory. It was not known whether the treatment could be made to work on
tumours inside the human body. The researchers reported that their next step was to see if the
process could be used to treat cancer in mice. In time and with much more research, this use of
nanoparticles may or may not prove useful in the treatment of cancer in humans.
Scientists tell the world about their work by publishing papers in scientific journals. They write a
scientific paper, which is a summary of their work, and then send it to a journal. The work is then
studied by other scientists to check if the evidence is strong enough and the work is scientifically
sound. If it is, the paper is then published in the journal. Some papers are not successful and are
not published. There are many different journals, each covering a different area of science. If a
paper is very important or of interest to the general public, news programmes or newspapers may
report the research.
1
What is cancer? (1 mark)
2
What do cancer treatments such as chemotherapy and radiotherapy try to do, and what
problem is there with these cancer treatments? (2 marks)
3
What are nanoparticles? (1 mark)
4
How did the researchers use nanoparticles to kill cancer cells, and why did the treatment not
kill healthy cells? (4 marks)
5
Is this treatment ready to use on humans? Explain your answer. (1 mark)
6
What is a scientific journal? (1 mark)
7
How are scientific papers checked before they are published? (1 mark)
Extension
8
Try and find out what has happened to follow-up this research since it was published.
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175
C2 2.6d – Student worksheet
Properties and uses of carbon nanotubes
The table compares the properties of carbon nanotubes with those of some other materials.
Property
Carbon nanotubes
Other materials
Strength
Up to 50 times stronger than highstrength steel
Kevlar is about 25 times stronger than
high-strength steel
Flexibility
Can be bent through large angles and
back to original shape with no change
Metals can be bent but are difficult to
return to their original shape
Density
About 1.35 g/cm3
Kevlar = 1.44 g/cm3
Carbon fibres = 1.75 g/cm3
Aluminium = 2.7 g/cm3
Conduction
of electricity
1000 times higher than pure copper
Pure copper has a high electrical
conductivity
Conduction
of heat
15 times higher than pure copper
Pure copper has a high thermal
conductivity
Cost
From £2000 per kilogram
Copper: about £4 per kg
Steel: about £0.40 per kg
1
2
For each of the following uses, give the advantages of using carbon nanotubes. Use the data in
the table to help.
a
Carbon nanotubes could be used to conduct the heat away from microchips. (1 mark)
b
Tennis rackets can be made from polymers that have been made by putting fibres inside
them. The manufacturer wants to use carbon nanotubes instead of the carbon fibres it
currently uses. (1 mark)
c
A manufacturer wants to make body armour using carbon nanotubes instead of a mixture
of Kevlar and metal plates. (2 marks)
d
Carbon nanotubes could be used to make transistors for computer chips. The size of the
smallest transistor on a chip is about 100 nm long, whereas a nanotube transistor would be
less than 10 nm long. (1 mark)
What is the main disadvantage of using carbon nanotubes? (1 mark)
Extension
3
The Nobel Prize for Physics in 2010 was awarded for research into the substance graphene.
Find out:
a
what graphene is. (1 mark)
b
how graphene is related to carbon nanotubes. (1 mark)
c
some potential uses of graphene. (2 marks)
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