NATIONAL QUALIFICATIONS CURRICULUM SUPPORT
Chemistry
Open-ended Questions
Support Materials
[REVISED ADVANCED HIGHER]
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Contents
Assessing insight, rewarding creativity
4
1.
The need for open-ended questions
4
2.
What makes a good open-ended question?
5
3.
Preparing learners to answer open-ended questions
5
4.
The marking of open-ended questions
7
5.
Example questions
8
6.
Marking guidance
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OPEN-ENDED QUESTIONS
Open-ended questions
Assessing insight, rewarding creativity
The Advanced Higher Chemistry examination has always contained a range
of question types. Some test knowledge and recall of chemical facts, whilst
others assess the learner’s ability to carry out calculations, interpret data,
write short explanations or design experiments. One type of question that is
new to the revised Advanced Higher is the open-ended question.
The purpose of this document is to introduce practitioners to the key features
of open-ended questions, to advise on how they can be used for teaching and
learning, and to provide guidance on assessment.
1.
The need for open-ended questions
In addition to providing learners with a sound knowledge and understanding
of key chemical facts and concepts, the Advanced Higher Chemistry course
develops a range of transferable skills identified as essential by both
employers and higher education.
To assess a learner’s overall attainment, a range of different question types is
employed in the course examination. Fixed-response, short-answer and
extended-answer questions, along with detailed marking instructions, prov ide
a reliable and robust assessment of a learner’s ability to recall key subject
knowledge and apply numerical and problem-solving skills within chemistry
contexts. These question styles will continue to form the core of the course
examination for the revised Advanced Higher Chemistry.
A principal objective of this revision of Advanced Higher Chemistry is to
promote a deeper understanding of the subject. Examination papers have
traditionally contained ‘explain-type’ extended-answer questions to probe
deeper understanding. However, this type of question might sometimes be
answered by recall of a well-rehearsed ‘stock-explanation’ without a learner
necessarily possessing an understanding of the underlying chemical
principle(s).
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The new-style open-ended question can be used to assess whether or not a
learner has truly grasped a chemical concept. In this type of question, the
learner is required to draw on his/ her understanding of key chemical
principles in order to solve a problem or challenge. The open -ended nature of
these questions is such that there is no unique correct answer. In addition to
testing the extent of a learner’s chemical insight, these questions promote and
reward creativity and analytical thinking. The less prescriptive marking
instructions focus on rewarding learners for their understanding of chemistry.
2.
What makes a good open-ended question?
Open-ended questions present a scenario or challenge that invites learners to
demonstrate their chemical insight.
1.
A good open-ended question presents a real-life context that is
interesting and relevant to the learner.
2.
All open-ended questions must have more than one possible answer.
Different learners may write totally different responses. However, as
long as these responses meet the assessment criteria then full marks are
obtainable. This set of criteria is demonstrated in the marking of openended questions section (page 7).
3.
Learners should be able to answer an open-ended question in around 5
minutes, so the question should be economically worded.
4.
The role of the open-ended question is to assess the key underlying
concepts of chemistry rather than the recall of a particular fact.
Learners should not be prevented from answering the question by
failing to recall a key piece of information. There should be several
routes into a good answer.
3.
Preparing learners to answer open-ended questions
Pilot trials of open-ended questions at Higher level were carried out in a
range of Scottish schools in 2010. These trials demonstrated that as well as
being an effective stimulus for discussion of key chemical concepts, open ended questions also provide excellent formative assessment opportunities
within the Higher Chemistry classroom. It is fair to assume that this will also
be true at Advanced Higher level.
The trials also indicated that the greatest challenge faced by learners when
tackling open-ended questions is in deciding what is being asked and
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formulating an answer containing enough relevant chemistry to gain full
marks.
The skills needed to make a success of open-ended questions can be
developed in the supportive context of a team-based activity. An open-ended
question is firstly presented to the whole class by the practitioner. Teams of
learners are then challenged to answer the question within a 5-minute period.
Each team shares their answers with the whole class. In this way, learners
gain an appreciation of the variety of ways in which an open -ended question
can be answered correctly.
In order to enable learners to gain an understanding of the assessment of
open-ended questions, teams can also be provided with a sample of learner
answers to a particular open-ended question and asked to sort them into rank
order from ‘no understanding ‘ to ‘good understanding’.
Open-ended questions can also be used effectively for revision or
consolidation purposes, to promote discussion and review of a topic or
concept.
In preparing for the course assessment, the following advice may prove useful
to pass on to learners:
1.
2.
3.
4.
5.
6.
7.
6
In Advanced Higher Chemistry examinations open-ended questions will
always be identified by the wording ‘Using your knowledge of
chemistry …’
Read the question carefully. Pay attention to diagrams, structural
formulae or equations that have been included to help you answer the
question.
There will not be a single ‘correct’ answer. Markers will reward your
understanding of chemistry.
Reflect on the information provided in the question. Make sure that you
answer exactly what the question is asking.
Show your understanding of chemistry by drawing structural formulae,
identifying functional groups, writing chemical equations or working
out formulae.
You may choose to present your answer as a paragraph, a set of bullet
points or even a diagram.
If you have time at the end of the examination, check to see if what you
have written answers the question asked.
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OPEN-ENDED QUESTIONS
4.
The marking of open-ended questions
Trials in Scottish schools confirmed that open -ended questions stimulate
learners to think creatively. An impressively diverse range of answers
demonstrating a very broad and deep understanding of chemical ideas was
produced. A sample of these answers is illustrated in the example questions
section of this document (page 8).
Given this diversity, it is impossible to predict all of the answers learners will
provide to produce a point-by-point marking scheme. As a result, a marking
model that dissects answers into lists of ‘correct facts’ and ‘mistakes’, each
carrying certain rewards or penalties, is unlikely to prove practical or fair.
Whilst detailed point-by-point marking instruction will continue to be
provided for other parts of the Advanced Higher Chemistry examination,
responses to open-ended questions will instead be marked against a set of
criteria. This relies on a marker’s professional judgment to assess the extent
of chemical knowledge and insight demonstrated by the learner and to assign
a mark accordingly.
It will not be necessary for a learner to produce an answer that is correct in
all respects to be awarded full marks. If an answer provides clear evidence
that a learner has a good understanding of the chemistry relating to the
question, it is entirely appropriate to award full marks.
A learner’s response to an open-ended question should be assigned a mark
according to how his/her understanding of chemistry matches the statements
below.
0 marks: The learner has demonstrated no understanding of the chemistry
involved. There is no evidence that the learner has recognised the area of
chemistry involved or has given any statement of a relevant chemistry
principle. This mark would also be given when the learner merely restates the
chemistry given in the question.
1 mark: The learner has demonstrated a limited understanding of the
chemistry involved. The learner has made some statement(s) that is(are)
relevant to the situation, showing that at least a little of the chemistry within
the problem is understood.
2 marks: The learner has demonstrated a reasonable understanding of the
chemistry involved. The learner makes some statement(s) that is(are) relevant
to the situation, showing that the problem is understood. There might also be
a statement of a chemistry principle such as an organic process , eg oxidation
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or hydrolysis, or of a relevant relationship between the var iables involved in
the problem.
3 marks: The maximum available mark will be awarded to a learner who has
demonstrated a good understanding of the chemistry involved. The learner
shows a good comprehension of the chemistry of the situation and has
provided a logically correct answer to the question posed. This type of
response might include a statement of the principles involved, a relationship
or an equation, and the application of these to respond to the problem. This
does not mean the answer has to be what might be termed an ‘excellent’
answer or a ‘complete’ one.
5.
Example questions
Open-ended questions are much more difficult to write than the more
common extended answer questions. Here are some suggestions:
1.
Transition metals and their compounds display a variety of colours, for
example when a sample of copper is held in a flame it produces a green
flame test. Aqueous solutions of copper compounds are blue. Adding
ammonia to these solutions gives a deeper blue colour.
Using your knowledge of chemistry, discuss why transition metals and
their compounds behave in this way.
The learner may wish to discuss why transition metal compounds are
coloured (d–d transitions and oxidation state). The energy difference in
d–d transitions is also influenced by the ligand position in the
spectrochemical series, eg the energy difference associated with the
ligands water and ammonia. Some ‘transition elements’ such as
scandium and zinc do not form coloured ions explained by either no d electrons or a complete d-subshell.
This question also gives the learners the opportunity to discuss the
nature of light and show their understanding of the emission and
absorption of light. Learners may wish to explain that coloured
solutions are produced by absorbing light and sh ould be able to explain
that when a colour is absorbed the complementary colour is observed.
Although learners are unlikely to quantify the energy emitted, they
could discuss how energy and wavelength are related.
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2.
Using your knowledge of chemistry, discuss the following molecule.
You may wish to discuss features such as functional groups, probable
chemistry, physical properties, isomers or spectroscopic features.
H
O
C
C
C
H
H
Learners can show their understanding of organic chemistry and
structural analysis. The molecule shown is cinnamaldehyde. It is
unlikely that learners would be familiar with this molecule or be able to
name it. However, they should be able to identify the phenyl group, the
unsaturated double bond and the aldehyde group. The expected infrared wave numbers for the functional groups or proton NMR chemical
shift values for the hydrogen atoms could be given. The molecule is a
liquid and only slightly soluble in water but learners are more likely to
mention that the formula mass is 132 g mol –1 and the formula is C 9 H 8 O.
Cis and trans isomers are possible and the most likely isomer is the
trans one shown. Addition reactions to double bonds and carbonyl are
possible (any correct suggestion with reagents). Oxidation and
reduction of the carbonyl functional group could also be discussed with
appropriate reagents. Learners may also wish to discuss the bonding, eg
delocalised electrons, conjugation, sigma and pi bonding and sp 2
hybridisation.
3.
A compound has the formula K 3 [Fe(CN) 6 ]. It has a melting point of
300°C and dissolves in water, forming a yellow solution. Using your
knowledge of chemistry, deduce from the compound as much chemical
information as you can.
This could yield a range of responses, including the oxidati on state of
the iron ion and its d-electronic configuration. Learners could also
discuss the stability of Fe 3+ due to the d-electronic configuration. The
name of the compound, potassium hexacyanoferrate(III) or the complex
ion, hexacyanoferrate(III) could be given and a structure drawn. Other
information such as its percentage composition, isomers, likely
reactions, octahedral geometry and so on could be discussed. Learners
may also discuss why the colour in solution is yellow in terms of d–d
transitions. The solubility and melting point suggest ionic bonding.
4.
Using your knowledge of chemistry, describe how to prepare a
carboxylic acid and discuss the chemistry of the chosen carboxylic acid .
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Learners may suggest any suitable method to prepare the carb oxylic
acid, eg oxidising primary alcohols and aldehydes with suitable
reagents or hydrolysing nitriles, esters or amides, again with suitable
reagents.
There are a range of responses that may be given to discuss the
chemistry, including carboxylic acids being weak acids, neutralisation
reactions and the pH of the salt formed, the role of carboxylic acids in
drug molecules, salt formation by reaction with metals or bases, ester
formation and amide formation. Any other relevant chemistry such as
other general reactions of acids would be acceptable.
5.
Chemicals in tea contribute to the colour when brewed. The colour in
tea is mainly from thearubigins and tannins. However, adding lemon
juice can lighten the colour and adding sodium bicarbonate can darken
the colour.
HO
OH
HO
O
O
O
O
O
O
O
-
O
OH
HO
HO
O
O
OH
OH
O
-
O
OH
+ 2H+
OH
HO
HO
OH
OH
OH
Thearubigin (colourless)
OH
Thearubigin anion (coloured)
Using your knowledge of chemistry, suggest reasons why tea is coloured
and why the colour may depend on the source of the water used.
The thearubigins are coloured in their anion form and behave as a
natural indicator. The acid in the lemon juice shift s the equilibrium to
the left, the colourless molecule, thearubigin. Sodium bicarbonate is a
base and reacts with the hydrogen ions in the molecules, shifting th e
equilibrium to the right and making the colour darker. Learners may
also state that the colour observed is white light minus absorbed colour
and suggest reasons, in terms of electrons, for the absorption of energy.
The water used may have a different pH and so also have an effect on
the equilibrium and the colour observed. Learners may use an equation
to
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represent the dissociation and write an expression for the equilibrium
constant, K. They could also discuss the energy difference between
HOMO and LUMO in the above structures and the absorption of visible
light by organic molecules.
6.
Titanium(IV) chloride is a colourless liquid at room temperature. It is
used in the production of titanium metal and titanium dioxide.
Using your knowledge of chemistry, discuss the chemistry of
titanium(IV) chloride and how you would determine the type of bonding
present.
Learners can give the oxidation state of titanium and the electronic
configuration of titanium(IV). They could also suggest a possible
structure.
A number of methods could be used, each one providing evidence of
either covalent or ionic bonding. Learners could suggest measuring the
melting point, boiling point, solubility, electrical conductivity as
dissolved, electrical conductivity as melt or re action with water.
Learners could also discuss ionic chlorides such as NaCl, covalent
chlorides such as CCl 4 or other titanium compounds such as TiO 2 .
7.
A mass spectroscopy experiment produced a parent ion with a mass of
156. Assume that the compound contains C, H and possibly O. Using
your knowledge of chemistry, suggest possible molecular formulae for
the ion fragment and how the actual structure could be determined by
spectroscopy and/or other chemical techniques.
Any combination of C, H and O that gi ves a mass of 156 would be a
suitable answer, eg C 11 H 24 , C 12 H 12 , C 11 H 8 O, C 10 H 20 O, C 9 H 16 O 2 ,
C 8 H 12 O 3 , C 7 H 8 O 4 or C 6 H 4 O 5 . To find out the actual structure more
information would be required, eg infra-red spectra, proton NMR
spectra or other appropriate method. Expected peaks in the mass
spectrum, infra-red spectrum or proton NMR spectrum of the suggested
compound may be given.
Chemical properties appropriate to the chosen molecules can also be
discussed.
8.
Using your knowledge of chemistry, suggest a method of producing
alcohols and how you could determine that you had produced this
alcohol.
Ethanol could be produced by fermentation of carbohydrate, acidcatalysed hydration of ethane, hydrolysis of esters, reduction of
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ethanoic acid, nucleophilic attack on chloroethane by OH – (aq),
hydrolysis of methane nitrile then reduction etc. or other suitable
method to produce ethanol. Reagents would be expected in a good
answer.
To identify the ethanol: Distillation to show that the substance boils at
78°C. Test flammability. Learners may give likely positions of peaks in
proton NMR spectrum, mass spectrum and/or infra-red spectrum.
9.
Electric sparks or arcs display blue hues of light in air. Using your
knowledge of chemistry, comment on the reasons why this occurs.
This question gives the learner the opportunity to show their
understanding of the key concepts covered in the electromagnetic
radiation section. Relevant and correct chemistry is expected. Learners
can discuss the nature of light and may suggest a suita ble wavelength
for the light (around the 400 nm range). This would allow them to
calculate the energy associated with this light or they may discuss how
energy is related to wavelength. Learners can show that they understand
how light is produced by describing the emission of photons from
excited electrons falling to lower energy states. The excitation energy
in this case would come from the electrical energy and the learners may
also mention that since nitrogen is the main component in air it is the
most likely source of the blue colour.
10.
A learner doing Advanced Higher Chemistry wrote ‘There are only two
types of arrows used in chemistry. The usual arrow, which represents
reactants turning into products, and a double arrow, which indicates that
a reaction is reversible or has reached equilibrium.’
Using your knowledge of chemistry, comment on the learner’s
statement.
This question gives learners the opportunity to show their
understanding of some key concepts in chemistry. Learners may explain
that an arrow represents a chemical reaction and suggests all reactants
are converted into products. However, many chemical reactions do not
give 100% products and are more accurately represented by a double
arrow. Learners with a deeper understanding may comment on the
difference between an open and a closed system, eg in rusting an
equilibrium is never established because it is an open system. Learners
can also use their knowledge of equilibrium to explain how an
equilibrium constant is calculated and what this means in practice.
Another route into this question would come from a learner disagreeing
with the statement and discussing curly arrow notation in organic
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chemistry. Here they would be expected to explain what these arrows
represent and how they are used in a reaction mechanism to show
electron transfer and bond formation. Diagrams and examples could be
used by the learner to illustrate the answer.
Single-headed arrows are also used to denote electrons in the orbital
box notation of electronic configuration.
11.
The equation for ammonia being made from nitrogen and hydrogen is :
N 2 (g) + 3H 2 (g)
2NH 3 (g) ΔH° = -92.22 kJ mol-1
‘Increasing the temperature and pressure and using a catalyst will
increase the value of the equilibrium constant, K, and so a larger yield
of ammonia will be produced.’ Using your knowledge of chemistry,
comment on this statement.
Learners will need to show that they have a good understanding of
equilibrium and can explain how the various factors influence the
equilibrium position. Equilibrium constants are not changed if you
change the concentrations of species present in the equilibrium, this is
effectively what happens as the pressure is changed . The only thing that
changes an equilibrium constant is a change in temperature. Learners
should be able to explain the effect of increasing the temperature based
on Le Chatelier’s Principle and the enthalpy value given. The catalyst
does not change the equilibrium constant but enables equilibrium to be
established more quickly. Other valid points would be acceptable and
learners may suggest what would happen to the yield, but this would
have to be judged in the context of the learners answer, as the
temperature and pressure would be competing factors affecting the
yield.
12.
Coca-Cola and Pepsi have changed the manufacturing process for their
drinks to bring their products in line with new legislation regarding
cancer-causing chemicals. The new process gives caramel colouring in
the drinks that has less 4-methylimidazole (4-MEI), a chemical which
California has added to its list of carcinogens. The structure of 4-MEI is
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Using your knowledge of chemistry, write down what you can about 4MEI.
Learners may give the molecular formula C 4 H 6 N 2 and its relative
formula mass 82 1. It is a heterocyclic organic molecule with a fivemembered diunsaturated ring structure composed of three carbon atoms
and two nitrogen atoms at non-adjacent positions. It also has a methyl
group.
Learners could suggest possible fragments in mass spectroscopy, peaks
in proton NMR spectroscopy or peaks in infra-red spectroscopy.
The lone pair of electrons on the nitrogen might suggest it is basic in
behaviour. The hybridisation and formation of sigma and pi bonds could
also be discussed. Any other relevant chemistry would be acceptable.
In answering open-ended questions it is hoped that learners will be able to
apply chemical knowledge and understanding to everyday situations.
In other types of open-ended question, information may be presented in
formats such as diagrams, pictures, tables and graphs. Learners will then be
required to analyse these and come to a relevant chemical conclusion.
Another type of question could invite learners to comment on the work of a
peer. This may be in the form of a laboratory report or simply recorded
results from an experiment.
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6.
Marking guidance
Responses should be marked according to the following criteria:
The learner has shown no understanding of the chemistry
Involved.
The learner has shown a limited understanding of the chemistry
Involved.
0 marks
1 mark
The learner has shown a reasonable understanding of the chemistry
involved.
2 marks
The learner has shown a good understanding of the chemistry
Involved.
3 marks
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