YEAR 11 UNIT ONE CHEMISTRY 2005 PRACTICAL WORK 1. All ...

1pracs2005
MELBOURNE HIGH SCHOOL
YEAR 11
UNIT ONE CHEMISTRY
2005
PRACTICAL WORK
Name
Teacher
_______________________________________
_______________________________________
1. All entries in this document must be made in ink.
2. Apart from recording observations and results,
instructions for marked pracs are NOT TO BE
ANNOTATED in any way whatsoever.
3. Replacement copies of this booklet (and the
marked prac report booklet) are available on the
Chemistry web page.
This booklet contains the following practical exercises:
• material analysis (E Glo)
• modifying metals (marked prac)
• structure of materials (conductivity)
• modelling structures
• molecular models
• alcohols
• investigating hydrocarbons (marked prac)
• linking of polymer chains
• tangling of polymer chains
• making polymers
• deriving a solubility curve (marked prac)
• precipitation reactions (marked prac)
• surface chemistry
NOTE : This booklet has:
• instructions and blank report forms for non-marked pracs
• instructions and results tables or results spaces but not the report forms for marked pracs

2
Before any practical exercise ensure that you:
• have read the exercise thoroughly and completely
• understand the theory behind the exercise
• are aware of the safety instructions relevant to the exercise
• have completed any necessary pre-prac calculations or predictions
(if there are any for that particular exercise)
• realised that, unless you have already had two pre-prac tests in the
semester, any exercise is fair game for an unannounced pre-prac
test

3
2005 MATERIAL ANALYSIS (E Glo)
E Glo is a newly-developed 'glow in the dark' silicone rubber. It is a polymer consisting of long chains
of covalently bonded alternating silicon and oxygen atoms with hydrocarbon side groups bonded to the
Si atoms. The glow is produced by impregnating the polymer with very small amounts of strontium.
The development of a wide range of products from E Glo is only possible if extensive experimentation
is carried out in order to determine the range of properties of the material. The test kit contains E Glo
in various forms and shapes, including off-cuts that come in their raw state directly from the machine
that produced the polymer. The Glo Doh is a silicone rubber that has not been placed under high
pressure to create shapes. All samples contain the same percentage of strontium.
Materials and Apparatus
Investigation
• safety goggles • hammer
• apron • scalpel or knife
• E Glo test kit • box with blackened interior
• cement bench mat • apparatus in the bench cupboard
Working in pairs, you are to:
• develop and trial a range of experiments to determine the properties of E Glo
• suggest a number of uses for this material
You will be using an E Glo test kit consisting of a variety of product samples and other materials that
will assist you in determining the properties of E Glo. The contents of the bench cupboards may be
used.
NOTE: Destructive tests must only be performed on very small samples of the
off-cuts.
Aim
Method
Results
.../over

4
Discussion
Possible uses for E Glo
Conclusion
End of experimental work and report

5
Background
2005 MODIFYING METALS
The properties of metals may be modified in various ways.
treatment and alloying.
Two commonly used ways are heat
The macroscopic properties of a metal will depend on its microstructure - the arrangement of its atoms
into crystals and the elements involved (ie atomic size).
When a metal is cooled slowly, the atoms have time (and sufficient energy during that time) to
rearrange themselves into larger crystals. When a metal is cooled quickly, it forms small crystals
instead. There are weaknesses where these small crystals adjoin one another and hence quenched
metals tend to be more brittle than those cooled slowly.
Alloys exist either as atoms of similar size replacing some of the original atoms in the lattice or, if
significantly smaller, occupying the existing spaces in the lattice. Consequently, these alloys have
different properties.
Safety
• goggles and an apron must be worn when handling needles and hot metals
• use metal tongs when handling hot objects
• disposal of used solids into the bins is vital – be especially careful of the needles
• lead is toxic ∴ wash hands more thoroughly than usual after handling lead and solder
Materials and Apparatus
Method
• safety goggles • spatula
• apron • metal tongs
• 4 g lead • matches
• 6 g tin • hammer
• 3 identical needles • bunsen burner, tripod and pipeclay
• 100 mL beaker triangle
• crucible (without lid) • 2 bench mats
• aluminium tray • tap water
Note: the tin and lead may already be weighed out for you and placed in plastic bags.
Heat treatment
1. Obtain three identical needles and put one needle aside as a control.
2. Using a non-luminous flame (blue), strongly heat another needle for about 1_ minutes then
place it on the cement bench mat and allow it to cool slowly.
3. Heat the remaining needle for a similar time. Then drop it into a 100 mL beaker of cold tap
water.
4. CARE! GOGGLES MUST BE WORN. When the needles are quite cool, try to bend and
break all three. Record your observations.
Alloying – solder production
1. Observe and record the properties listed in the results table (on the next page).
2. Check that your crucible sits in the pipeclay triangle and does not fall through.
3. Roll the tin and lead together into a ball and place it in the crucible.
4. Heat the crucible briefly using the non-luminous flame until a uniform molten mixture is
obtained. Stir the molten metal with a spatula and remove any oxide coating from the top of
the molten metal. [NB: one end of the spatula will become very hot!]
5. Using metal tongs, carefully pour the molten solder into an aluminium tray that is sitting on a
second bench mat. If necessary, flatten the solder with a hammer. When cool, check the
solder and add its properties to your results table.
6. Arrange a small piece of each metal and solder in an equilateral triangle on the aluminium
tray. Heat the centre of the tray and record the order of melting.
7.
.../over
Results

6
Heat treatment
Needle
Observations
control
slow cooling
rapid cooling
Alloying
Metal Hardness Appearance Other observations
tin
(Sn)
lead
(Pb)
solder
Order of melting: 1st _______________ 2nd _______________ 3rd _______________
End of experimental work
2005 STRUCTURE OF MATERIALS (CONDUCTIVITY)

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Background
Metals and non metals combine in various ways to form 5 kinds of structures:
• metallic elements
• non metallic elements
• compounds of non metallic elements
• compounds of metallic and non metallic elements
• compounds of metallic elements (alloys)
This exercise investigates 4 of these 5 categories of substances.
These categories may be distinguished according to different combinations of their physical properties,
especially their melting temperatures and electrical conductivities. These properties are explained in
terms of the bonding present in the substance.
This exercise investigates the electrical conductivity of selected substances in one or more phases:
• solid
• liquid (referred to as molten if the substance is not a liquid at room temperature)
• aqueous solution (dissolved in water)
• organic solution (dissolved in an organic solvent)
Safety
• sulfur and naphthalene must be heated carefully in a fume cupboard and not in the open
laboratory - both are flammable
• solid iodine is corrosive and stains; iodine solution stains and the vapours are toxic - do
not inhale
• cracked test tubes - if any - must be disposed of as directed
• power packs must be switched off before moving to the next location
Materials and Apparatus
Method and results
• power packs • copper foil
• alligator clips • tin foil
• leads • ethanol
• ammeters and/or milliammeters • sucrose (solid and aqueous solution)
• 100 mL beakers • iodine (solid and organic solution)
• large paper clips (for use as electrodes) • sulfur (solid and molten)
• meker burner • naphthalene (solid and molten)
• bunsen burner, bench mats, matches • potassium iodide (solid, molten and
• wire coat hanger electrodes aqueous solution)
• display galvanometer or ammeter • copper(II) sulfate (solid and aqueous
• separators solution)
Note:
If you get all substances to conduct electricity in all the phases tested, then something is
seriously wrong with the exercise!
The various materials are set up at stations around the room - sulfur and naphthalene are in the rear
fume cupboard and molten potassium iodide will be done as a teacher demonstration.
Move around the room to each station. At each station, switch the power pack on, record the current
flow, switch off the power pack and move to another station. Remember to check whether an ammeter
or a milliammeter is in use a particular station and record the appropriate unit for the current.
.../over

8
When at the fume cupboard, test the conductivity of the solids and leave the power pack on when
heating the solids. The substances may shrink when heated so ensure that the electrodes remain in the
liquid. As soon as you've checked the conductivity of the molten materials, turn the bunsen burner off.
Substance and
Ability to conduct electricity when
formula solid liquid/molten dissolved in
solution
copper (Cu)
copper(II) sulfate (CuSO 4 )
ethanol (CH 3 CH 2 OH)
iodine (I 2 )
naphthalene (C 10 H 8 )
potassium iodide (KI)
sucrose (C 12 H 22 O 11 )
sulfur (S)
tin (Sn)
metallic elements
melting temp.
electrical conductivity
(high or low) solid liquid/molten solution
non metallic elements
compounds of
non metals
compounds of metals
and non metals
Questions
1. Which substance had mobile charges in the liquid and solution phases but not in the solid state
Explain this in terms of the structure of the substance.
2. What type of melting point did those substances that did not conduct in any state tested exhibit
Why is this the case
3. In which category/ies of substances are there particles that are held together only weakly
End of experimental work and report
2005 MODELLING STRUCTURES

9
Atomic structure
Brief description and/or diagram of the model:
What are the limitations of this model
Metal structure
Brief description and/or diagram of the model:
What properties of metals may be explained by this model
What are its limitations (ie what properties can't it explain)
NaCl structure
Brief description and/or diagram of the model:
What type of bonding is represented
__________________________________
What properties of NaCl may be explained by this model
What are its limitations
CO 2 structures (2 models)
.../over

10
Brief description and/or diagram of the models:
What type(s) of bonding is/are represented _____________________________________________
What properties of CO 2 may be explained by these models
What are their limitations
Diamond structure
Brief description and/or diagram of the model:
What type of bonding is represented ______________________________________
What properties of diamond may be explained by this model
What are its limitations
Graphite structure
Brief description and/or diagram of the model:
What type(s) of bonding is/are represented _____________________________________________
What properties of graphite may be explained by this model
What are its limitations
End of exercise
2005 MOLECULAR MODELS

11
Standard colour coding for molecular models:
• hydrogen - white • carbon - black • oxygen - red
• sulfur - yellow • nitrogen - blue • halogens - green
Number of prongs on clusters:
• 1 - linear (one covalent bond only) • 2 - linear (may represent a triple bond)
• 3 - triangular planar (may represent a
double bond)
• 4 - tetrahedral
Length of straws:
• long - lone pair or single bond representing 1 pair of electrons
• medium - double bond representing 2 pairs of electrons
• short - triple bond representing 3 pairs of electrons
Hints for determining molecular shape:
1. Decide which is the central atom; write out its configuration.
2. Write out the configuration of the other elements; determine the number of electrons these
atoms need to share in order to obtain a stable configuration.
3. Determine how many electrons the central atom contributes.
4. Decide whether bonds are single, double or triple and whether there are lone pair(s).
5. When deciding the shape, remember that the electron pairs will be as far away from each other
in 3-dimensional space as possible and that only the relative positions of the nuclei are used to
define the shape.
6. Use the shape chart to determine the molecular shape. [Note that lone pairs are omitted from
the diagrams.]
Method
1. Check that the jar containing the model components is complete according to the list on the
jar.
2. Construct each model and draw the structural formula in the space provided in the table on the
next page - use chemical symbols rather than circles to represent nuclei and inner shell non
bonding electrons. [Lone pairs must be included where they affect the shape of the species.]
3. Where possible, determine the shape of the molecule and write it in the structural formula box.
4. Dismantle all components and check that the contents of the jar are still correct.
…/over
Results

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H 2 O
CH 4
NF 3
shape:
N 2
shape:
CO 2
shape:
HCl
shape:
BF 3
shape:
H 2
shape:
O 2
shape:
C 2 H 6
shape:
C 2 H 4
shape:
CHCl 3
Question
shape: not possible
shape:
shape:
Why is it not possible to describe the shape of the ethane molecule
End of exercise and report
2005 ALCOHOLS

13
Alcohols are characterised by the presence of the hydroxy group, ⎯OH. The parent alcohol is
methanol, CH 3 OH, and the most common one (and least toxic one, too) is ethanol, CH 3 CH 2 OH.
As the length of the carbon chain increases, the solubility of the alcohol in water decreases.
Models
1. Check that the jar containing the model components is complete according to the list on the
jar.
2. Construct models of methanol and ethanol and draw their structural formulae in the space
provided in the table. [Lone pairs must be included where they affect the shape of the
species.]
3. There are two structural isomers of propanol, ie propan-1-ol and propan-2-ol. Both have the
molecular formula C 3 H 8 O. Construct models of the isomers of propanol and draw their
structural formulae.
4. Dismantle all components and check that the contents of the jar are still correct.
propan-1-ol
propan-2-ol
semistructural
formula:
semistructural
formula:
Experimental
Safety
• an apron must be worn
• alcohols are both toxic and flammable
• sulfuric acid is corrosive
• potassium dichromate is an oxidising agent
• food colouring will stain clothes, paper, skin, the bench, reputations, etc.
Materials and Apparatus
Method
• apron • food colouring
• ordinary test tubes and rack • methanol
• micro test tubes, rack and brush • ethanol
• 100 mL beaker • 0.1 M K 2 Cr 2 O 7 solution
• hot water • dilute sulfuric acid
1. Solubility in water
* Place a few drops of methanol and ethanol into separate micro test tubes. Add 2 drops of
food colouring to each. Shake.
* Are methanol and ethanol soluble in water Yes / No (strike out the incorrect answer)
* Empty the micro test tubes and clean with the small brush.
2. Reaction with acidified potassium dichromate solution - this reaction is the breathalyser
reaction for the detection of drunk drivers.
.../over

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* place potassium dichromate solution in an ordinary sized test tube to a depth of about 2 cm.
Carefully add about 1 cm in depth of dilute sulfuric acid. Next add a few drops of ethanol.
Shake the test tube carefully then place it in a 100 mL beaker of warm to hot water.
* record colour changes over about 5 minutes.
* using one hand, waft some vapour from the test tube to your nose. Do not snort! Record
odour changes over time.
* rinse the test tube and put all equipment away.
Colour changes: ____________________________________________________________________
Odour changes:
____________________________________________________________________
Questions
1. Can you write an equation that explains the reaction between ethanol and acidified potassium
dichromate solution Yes / No (There is no penalty for being honest, only for lying.)
My attempt is: (Your teacher may assist you.)
________________________________________________________________________________
Working space for your equation:
2. Why does the solubility of alcohols in water decrease as the length of the hydrocarbon chain
increases
3. Why is ethanol soluble in water whereas ethane is not
End of experimental work and report
Background
2005 INVESTIGATING HYDROCARBONS

15
Hydrocarbons are organic compounds composed only of carbon and hydrogen. They are non-polar
molecules are therefore are soluble in non-polar solvents. Hydrocarbons have no functional groups.
When they undergo complete combustion, they form only carbon dioxide and water. However, if the
combustion is incomplete, they form carbon (or carbon monoxide) and water. The main component of
natural gas is methane, CH 4 .
A saturated hydrocarbon has only single covalent bonds between the carbon atoms. If a hydrocarbon
is unsaturated, then it has a double or triple bond between at least two of the carbon atoms. If bromine
solution reacts rapidly with a hydrocarbon, then the hydrocarbon must be unsaturated. The distinctive
colour of the bromine disappears as the double (or triple) bond in the hydrocarbon is converted to a
single bond and a bromine atom is added to each of the carbon atoms that were originally involved in
the double bond.
Safety
• bunsen burners must be used first and put away before any liquid or solid
hydrocarbons are used by any student
• hydrocarbon residues must be poured into the organic residue bottle in the fume
cupboard and NOT poured down the sink
• bromine solution is corrosive and readily absorbed through the skin
• organic bromine compounds may cause impotence (and we don’t want any embarrassment)
• goggles and aprons must be worn
• exhaust fans should be switched on (NOT the normal ceiling fans - why not)
Materials and Apparatus
Method and Results
• small bunsen burner • cement bench mat
• cyclohexane • test tubes and rack (for bunsen test)
• cyclohexene • micro test tubes and rack (for
• naphthalene hydrocarbons tests)
• dropping bottle of food colouring • wooden test tube holder
• bromine dissolved in hexane or • matches
heptane • goggles
• small spatula • apron
• organic residue bottle
A. Combustion of hydrocarbons
Light a small bunsen burner with the air hole closed so that a luminous (yellow safety) flame is
obtained. Using a wooden test tube holder in the prescribed manner (ie with the holder close to the
open end and the test tube inclined at an angle of about 45 o ), hold the test tube in the flame for about
30 s. Record your observations. Open the air hole and heat the test tube for a couple of minutes in
the non-luminous (blue) flame. Record your observations.
ALL students must return the bunsen burner, etc., to the correct place in
the cupboard BEFORE ANYONE starts parts B and C.
Air hole
Observations
closed
open
.../over
B. Solubility of hydrocarbons in water

16
Mix 10 drops of drops of each liquid hydrocarbon or a tiny piece of a solid hydrocarbon separately
with 10 drops of coloured water in micro test tubes.
Hydrocarbon
Observations
cyclohexane
C 6 H 12 (l)
cyclohexene
C 6 H 10 (l)
naphthalene
C 10 H 8 (s)
C. Saturation and unsaturation in hydrocarbons
Place 10 drops of drops of each liquid hydrocarbon or a tiny piece of a solid hydrocarbon separately in
micro test tubes. Add a few drops of bromine solution to each test tube.
Return all cleaned apparatus, chemicals, etc., to the correct place and clean the bench.
Hydrocarbon
Observations
cyclohexane
C 6 H 12 (l)
cyclohexene
C 6 H 10 (l)
naphthalene
C 10 H 8 (s)
End of experimental work
Background
2005 LINKING POLYMER CHAINS (SLIME)

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Polyvinyl alcohol is an addition polymer formed from vinyl alcohol (its systematic name is ethenol).
The polymer dissolves in water because the ⎯OH groups form hydrogen bonds with the water
molecules.
The addition of borax solution to a polyvinyl alcohol solution creates cross-links between the alcohol
chains and the tetraborate ions, B(OH) 4 - , present in the borax solution.
The result is a gel (pronounced "jell") in which the water molecules are trapped between the polymer
chains - about 95% of the gel is water.
Unlike the cross-links formed by covalent bonds, the links in the gel break and reform easily giving the
material some interesting physical properties. The gel behaves as a non-Newtonian liquid - it flows
when pulled gently apart and snaps if pulled sharply. If the slime is poured from its container and the
container tipped upwards slightly, the gel self-siphons. A lump of slime placed in a container slowly
flows to fit the container and one placed on the bench slowly spreads out.
The food colouring is used simply to improve the appearance of the slime.
H H H H H H H H H H
⏐ ⏐ ⏐ ⏐ ⏐ ⏐ ⏐ ⏐ ⏐ ⏐
Polyvinyl alcohol is ⎯ C ⎯ C ⎯ C ⎯ C ⎯ C ⎯ C ⎯ C ⎯ C ⎯ C ⎯ C ⎯
⏐ ⏐ ⏐ ⏐ ⏐ ⏐ ⏐ ⏐ ⏐ ⏐
H OH H OH H OH H OH H OH
Safety
• borax is toxic - it is used as an ant killer
• food colouring stains clothes, paper, skin, the bench, etc., as it is a dye
• hands must be washed more thoroughly than usual at the end of the exercise
• aprons must be worn
Materials and Apparatus
• apron • 100mL measuring cylinder
• 100 mL beaker • 4% borax solution
• glass stirring rod • 6% polyvinyl alcohol solution
• 10mL measuring cylinder • red or green food colouring
NOTE: The polyvinyl alcohol solution may be labelled Solution A, the borax solution may
be labelled Solution B and the food colouring may be labelled Solution C.
Method
.../over
*** In this exercise, the proportions of the solutions used must be adhered to or your slime will be

18
less than perfect (and rather messy, too)
1. Use the 100 mL measuring cylinder to add 20 mL of polyvinyl alcohol solution to a 100 mL
beaker. Add 3 drops of food colouring.
2. Use the 10 mL measuring cylinder to add 4 mL of borax solution to the beaker. Stir the
mixture thoroughly to produce your slime.
3. Remove the slime from the beaker and explore its properties - the slime will be less sticky if
your hands are clean and dry.
4. Clean the beaker, both measuring cylinders and stirring rod, invert the beaker in your
cupboard, return solutions to the designated place, wipe down the bench and wash your hands
more thoroughly than usual.
Observations and questions
1. Compare the properties of polyvinyl alcohol solution and slime:
Properties of polyvinyl alcohol solution
Properties of slime
2. Why is polyvinyl alcohol soluble in water
3. Compare the physical properties of polymers that are cross-linked by frequent covalent bonds
with those of slime.
4. What common polymers contain hydrogen bonds between their chains
End of experimental work and report
2005 TANGLING OF POLYMER CHAINS
The amount of tangling that occurs between polymer chains depends on the size of the polymer.

19
Materials and Apparatus
Method
• reel of cotton • metre rule
• 2 × 250 mL conical flasks with • tweezers
stoppers • 100 mL measuring cylinder
• scissors • tap water
• glass stirring rod
1. Cut 24 pieces of cotton 10 cm in length and 6 pieces 40 cm in length.
2. Place the short lengths of cotton in one conical flask and the long pieces in the other conical
flask. Add 100 mL of tap water to each flask, stopper the flasks and shake each one for 90 s.
3. Use the glass rod to remove the cotton from each conical flask and gentle squeeze out the
excess water from each bundle. Using the tweezers only, separate the treads of cotton in each
of the bundles.
4. Place used cotton in the bin, return the apparatus to the correct place and wipe down the
bench.
Questions
1. What effect does the length of the treads have on the ease of removal of the cotton pieces
from the bundle
2. What difference would you expect between the tangling of large and small polymers
End of experimental work and report
A. Urea-formaldehyde plastic
2005 MAKING POLYMERS

20
NOTE: Due to health concerns with the use of methanal (formaldehyde), this part of the exercise will
be done as a teacher demonstration. However, students are required to answer the questions.
If a polymer does not melt on heating but only chars, then it is a crosslinked (covalent bonding and no
discrete chains) thermosetting polymer. If it softens when heated and hardens again on cooling, then it
is a thermosoftening (thermoplastic) polymer with only weak interchain bonding (dispersion forces,
hydrogen bonding, tangling).
Safety
• methanal (formaldehyde) is a suspected carcinogen
• large amounts of heat and very unpleasant fumes are released when the reaction occurs
• concentrated sulfuric acid is an excellent dehydrating agent - it will dehydrate and
severely burn you if it comes into contact with your skin, clothes, etc. The bench will
also be damaged. If any is spilt, flood it immediately with vast amounts of water,
advise your teacher and then clean up the mess.
• aprons and goggles must be worn
Materials and Apparatus - teacher demo only
Method and Results
• goggles • electronic balance
• apron • 10 mL measuring cylinder
• heat resistant container • metal tongs
• stirring rod • urea
• spatula • formaldehyde solution (methanal)
• watch glass • dropping bottle of concentrated
• bench mat sulfuric acid
1. Pour 6 mL of methanal (formaldehyde) solution into a suitable heat resistant container. Add
3 g of urea and stir until a saturated solution is obtained.
2. Carefully add a few drops of concentrated sulfuric acid and stir the mixture. The mixture
should harden quite suddenly.
3. Thoroughly wash and dry the solid.
4. Use tongs to hold a small piece of the dried solid in a bunsen flame.
a/ i. What colour is the polymer ________________________________
ii. Is the polymer hard or soft
iii. What type of polymer is urea-formaldehyde
________________________________
________________________________
iv. Does this polymer contain linear or crosslinked chains How do you know
b/ Draw the structural formula of:
i. urea CO(NH 2 ) 2 ii. methanal (formaldehyde) HCHO
c/ Methanal reacts with water to form methandiol, CH 2 (OH) 2 , which is the species that reacts directly
with the urea molecules.
i. Draw the structural formula of methandiol.
.../over

21
ii. What structural feature (relevant to polymerisation) is exhibited by both urea and
methandiol molecules
B. Making nylon: preparation of a synthetic fibre
A fibre is composed of polymer molecules aligned so that effective forces of attraction exist along
significant portions of its length. A fibre is at least 100 times long as it is wide.
One of the first fully synthetic fibres was nylon. There are several varieties of nylon, each having
slightly different monomers and, therefore, slightly different properties. Normally, nylon is made by
reacting 1,6-diaminohexane (hexamethylene diamine) with a diacid such as sebacic acid. However, to
increase the reaction rate, we will use decan-1,10-dioyl chloride (sebacoyl chloride), which is similar in
structure, in place of sebacic acid.
Hexamethylene diamine is H 2 N.(CH 2 ) 6 .NH 2 and sebacoyl chloride is ClOC.(CH 2 ) 8 .COCl.
Nylon is a condensation polymer. As suggested by the numbers, nylon 6,10 is made from a six-carbon
and a ten-carbon monomer. When these combine, HCl is the small molecule eliminated.
Safety
• gloves, aprons and goggles must be worn
• both monomers (hexamethylene diamine and sebacoyl chloride) are skin irritants
• used solutions must be placed in the organic residue bottle
• hand must be washed more thoroughly than usual at the end of the exercise
Materials and Apparatus
• goggles • organic residue bottle
• apron • sebacoyl chloride solution (dissolved
• gloves in an organic solvent)
• 100 mL beaker • hexamethylene diamine solution
• 2 × 10 mL measuring cylinders (dissolved in water)
• glass stirring rod • tray for drying nylon
• tweezers
Method
.../over
1. Using a 10 mL measuring cylinder, transfer 10 mL of hexamethylene diamine solution into a
100 mL beaker. Using a different 10 mL measuring cylinder, measure out 10 mL of sebacoyl
chloride solution.

22
2. Hold the beaker at an angle of about 45 o . Slowly and carefully pour the sebacoyl chloride
solution down the side of the beaker so that it forms a layer on top of the hexamethylene
diamine solution . The solutions do not mix but a small amount of solid will form at the
interface.
3. Using a pair of tweezers, pull out a little of this solid and wind this nylon fibre along the
length of a glass rod - do not let the any of the fibre overlap. Wind as much nylon from the
interface as possible. Carefully rinse the nylon with tap water, remove it from the rod and
place it on the tray, as directed, to dry.
4. Stir the used solution and a lump of nylon may form. Rinse it and add it to your fibre on the
tray.
5. The used solution must be poured into the organic residue bottle in the fume cupboard and
not down the sink.
6. Clear away the equipment. rinsing the measuring cylinders very thoroughly. Wash your
hands more thoroughly than usual before leaving.
7. When dry, heat a small amount of your nylon in a bunsen flame.
Questions
1. Both monomer molecules are polar and have large non-polar regions, so why is the sebacoyl
chloride solution made up in an organic solvent whereas the hexamethylene diamine solutions
uses water as the solvent
2. Use the formulae of the nylon 6, 10 monomers to draw a section of the nylon polymer
showing three (3) amide linkages.
3. What happened when the nylon was heated
4. What is the major type of bonding found between nylons chains Why is this the case
End of experimental work and report
2005 DERIVING A SOLUBILITY CURVE
The solubility of a solute tells us the maximum amount of solute that can dissolve in a given amount of
solvent at a given temperature.

23
In this exercise, you will be determining the solubility of potassium nitrate (in g of potassium nitrate
per 100 g of water) at various temperatures and graph the results.
You will need to assume that the density of water 1 g mL -1 at all temperatures. Although the density
of water does vary with temperature, it is a reasonable approximation to make in view of the other
errors associated with this determination. Therefore, when 5.00 mL of water is added to the solute, it
can be said to be equivalent to the addition of 5.00 g of water, and so on.
Safety
• aprons must be worn
• the test tube must be heated in a water bath and not directly in a bunsen flame
• self-emptying test tubes indicate carelessness - wipe up any spillage immediately and
put the damaged test tube in the glass bin
Materials and Apparatus
Method
• apron • bunsen burner, tripod, gauze
• large test tube • spatula
• burette, stand and small funnel • KNO 3 crystals
• 500 mL beaker • ice
• -10 - 110 o C thermometer • deionised water
• electronic balance • tap water
• bench mat • matches
• large jar for collecting the used KNO 3 solution
1. Weigh accurately approximately 6.5 g of solid potassium nitrate into a large test tube.
Record the mass to 3 decimal places.
2. Use a burette to deliver exactly 5.00 mL of deionised water into the test tube.
3. Immerse the test tube in a large beaker containing about 250 mL of boiling tap water and
gently stir the contents using the thermometer until all the crystals have dissolved.
4. Remove the test tube from the boiling water and continue to stir gently until the first signs of
crystallisation are detected. Record the temperature at which the crystals start to form.
5. Add a further 3.00 mL of deionised water from the burette into the test tube and repeat Steps 3
and 4.
6. Repeat Step 5 as many times as necessary until the stage is reached that crystallisation won't
occur even when ice is used to cool the solution.
7. Pour your KNO 3 solution into the large collection jar provided.
8. Leave the burette set up on the bench, clean away all other equipment and wipe down the
bench.
Results and Calculations
*** the results table is on the next page
• the solubility of, say, 6.500 g of potassium nitrate dissolved in 5.00 g of water is equivalent to
as solubility of (6.500 × 100) ÷ 5.00 = 130 g per 100g
• complete your results table on the report form
• draw your graph with the independent variable (temperature) on the horizontal axis
Mass of KNO 3
(g)
(constant)
Total volume of water
(mL)
Temperature at which
crystals first form
( o C)
.../over

24
End of experimental work
2005 PRECIPITATION REACTIONS
When two solutions of ions are mixed, the resulting solution may instantaneously become
supersaturated with a newly formed compound. If this occurs, a precipitate will form. For example, if
a solution of Ba 2+ 2-
ions (eg BaCl 2 ) is added to a solution of SO 4 ions (eg Na 2 SO 4 ), the resulting

25
mixture will be supersaturated with respect to BaSO 4 . A precipitate of BaSO 4 will form until the
solution is saturated. The ionic equation for the reaction is:
Ba 2+ (aq) + SO 2- 4 (aq) → BaSO 4 (s)
Safety
• aprons must be worn
• compounds of lead and barium are toxic
• silver nitrate solution stains, clothes, paper, skin, the bench, etc., but it does so slowly
and not obviously
• silver nitrate crystals can burn the skin
• any spillages - especially silver nitrate solution - must be cleaned up immediately
Materials and Apparatus
Method
• apron • 0.1 M potassium iodide
• micro test tubes and rack • 0.1 M silver nitrate
• micro test tube brush • 0.1 M potassium chromate
dropping bottles containing: • 0.1 M copper(II) sulfate
• 0.1 M sodium carbonate • 0.1 M barium chloride
• 0.1 M lead(II) nitrate
Precipitate predictions must be made in INK prior to
the exercise being done in class. No alteration to
your predictions will be permitted.
1. Before the prac class, predict the precipitate, if any, that will form when the following
solutions are mixed and record your predictions in the table on the next page:
• lead(II) nitrate and sodium carbonate
• lead(II) nitrate and potassium iodide
• sodium carbonate and potassium iodide
• silver nitrate and potassium iodide
• silver nitrate and potassium chromate
• lead(II) nitrate and silver chromate
• copper(II) sulfate and sodium carbonate
• copper(II) sulfate and barium chloride
• lead(II) nitrate and barium chloride
• barium chloride and potassium chromate
• barium chloride and silver nitrate
• copper(II) sulfate and lead (II) nitrate
2. Mix the pairs of compounds by adding a few drops of each to separate clean micro test tubes.
Record your observations.
3. Use the micro test tube brush to thoroughly clean the micro test tubes and, when clean, place
them upside down in the micro test tube rack to drain.
4. Return the dropping bottles to the correct container on the side bench.
*** the predictions and results table is on the next page
.../over
Results
Reagents Predicted ppt. Observations

26
Pb(NO 3 ) 2
and
Na 2 CO 3
Pb(NO 3 ) 2
and
KI
Na 2 CO 3
and
KI
AgNO 3
and
KI
AgNO 3
and
K 2 CrO 4
Pb(NO 3 ) 2
and
K 2 CrO 4
CuSO 4
and
Na 2 CO 3
CuSO 4
and
BaCl 2
Pb(NO 3 ) 2
and
BaCl 2
BaCl 2
and
K 2 CrO 4
BaCl 2
and
AgNO 3
CuSO 4
and
Pb(NO 3 ) 2
Note :
If a precipitate is formed in the third test, then either you have the wrong solution(s) or your
test tube has not been thoroughly cleaned.
End of experimental work
2005 SURFACE CHEMISTRY
Safety
• an apron must be worn

27
• as this exercise is rather messy, a clean and safe working environment is even more
important than usual
• capillary tubes are fragile
• the dye mixture will stain skin, clothes, the bench, paper, etc.
• use the organic residue bottle as directed
Materials and Apparatus
• apron • butter, milk, shaving cream
• deionised water • paraffin oil
• detergent solution • stoppers for test tubes
• cooking oil • tweezers
• microscope slides • capillary tubes
• pieces of ceramic • metal washers
• wax • disposable plastic petri dishes
• lycopodium or sulfur powder • droppers
• powdered dye mixture containing • small spatula
methylene blue and Sudan IV • organic residue bottle
Method
A. Wetting
Place one drop of the liquids listed in the results table on the surface specified. Draw the appearance
of the liquid drop when it is on the surface.
deionised water
glass ceramic wax
detergent solution
cooking oil
B. Surfactants
1. Fill a beaker with water. Sprinkle lycopodium powder or powdered sulfur on the surface of the
water. Add 1 drop of detergent to the centre of the water.
2. Fill a petri dish to overflowing with water. Use a ruler to quickly scrape off the liquid from the top
of the petri dish (and wipe up any mess!) . Record the number of metal washers that can be added
using tweezers before the water overflows. Repeat but add 6 drops of detergent to the water before
adding the washers.
3. Carefully position a capillary tube so that one end is just below the surface of water and measure the
height of the water in the capillary. Do the same using concentrated detergent solution.
*** The results table is on the next page.
Test Observations Explanation
.../over
lycopodium or
sulfur powder

28
washers
number in water =
number in detergent =
capillary tubes
height in water =
height in detergent =
C. Emulsions
• The dye mixture contains a water-soluble blue dye and an oil-soluble red dye. [Of necessity,
the dye mixture will stain everything! You have been warned - twice.]
1. Measure 3 mL of water and 3mL of paraffin oil into the same test tube. Stopper and shake
vigorously. Allow to stand for a brief period and record observations. Add 3 drops of detergent and a
tiny amount of the dye mixture, stopper, shake, allow to stand and record observations.
2. Using a glass stirring rod, mix a tiny amount of the dye mixture with a small amount of each of the
emulsions listed into the one petri dish and hence determine the type of emulsion.
3. Dispose of the used petri dish into the rubbish bin
Test Observations Explanation
water and paraffin oil
water, paraffin oil and
detergent
emulsions:
type of emulsion:
butter
milk
shaving cream
End of experimental work and report