SALTERS ADVANCED CHEMISTRY

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SALTERS ADVANCED CHEMISTRY

• Feedback Meeting 2005
• Coursework

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AS Coursework 2852/02

• Experimental Skills

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Grade Boundaries

• Unchanged from last year
• Grade A - 38 out of 45
• Grade E - 25 out of 45

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Mark Changes As A Result Of Moderation

• 379 Centres marks unchanged
• 79 Centres marks reduced (17 of total)
• 0 Centre marks increased

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Mark Changes As A Result Of Moderation

• All Centres are allowed a tolerance before
  marks are changed
• Tolerance is or 3. Changes are made when the
  Centre marks are on average or 4 or more
  different from agreed moderation standard
• Changes are usually applied to ALL candidates

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Mark Changes As A Result Of Moderation
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Mark Scheme

• Centres need to check that they are using an up
  to date mark scheme
• Since the activity is brief and narrow the mark
  scheme should be applied rigidly i.e. all precise
  descriptors are met to reach a particular level

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Assessment Activity

• Most Centres use activities from OCR coursework
  guidance booklet
• Many Centres use just one activity

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Planning

• The quality of risk assessments and references is
  a key area for development in many Centres,
  particularly in the use of Haz Cards and web
  addresses.
• References to the internet should include a short
  description of the content of the web site as
  well as the web address

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Ref 1 Chemical Ideas, Burton et al, 1.5
Concentrations of solutions, p12
Ref 5 CLEAPSS Hazcards No. 98 Sulphuric acid
Ref 9 Information about acid base
indicators www.chemguide.co.uk/physical/acidbasee
qia/indicators
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Risk Assessments

• R.A. must cover all aspects for 11 marks
• No R.A.at all maximum of 4 marks !!!!
• R.A. covering most aspects maximum of 8 marks

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Encourage your students to
Identify any hazardous chemicals you will use or
make
OR hazardous procedures you will use
Record the nature of the hazards (CLEAPSS
Hazcards)
Decide what protective/control measures need to
be taken
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BASIC Wear safety glasses because sulphuric acid
is being used
BETTER At the concentration being used, sulphuric
acid is an irritant wear safety glasses
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• GOOD
• Sulphuric acid is an irritant wear safety
  glasses.If the acid is splashed into the eyes,
  flood the eye with gently running tap water for
  ten minutes and seek medical attention. If the
  acid is spilt onto the skin, again flood the area
  with running tap water.

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Implementing

• All burette readings needed, not just titres
• Burette readings should be recorded to 2 decimal
  places
• Units are needed for all measurements

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For volumetric data, initial and final burette
readings, not just the titre, should be
recorded, with units, and all to ? 0.05
cm3 Titration Rough 1 2 Initial
burette reading/ cm3 0.00 22.50 0.25 Final
burette reading/ cm3 22.50 44.65 22.35 Titre/
cm3 22.50 22.15 22.10
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Implementing

• No units at all
• maximum of 4 marks !!!!
• Burette only to 1 decimal place
• maximum of 10 marks

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Implementing

• Readings to find mass of sodium carbonate are
  needed (acid rain) This is a key area for
  development in some Centres
• Need to record all temperatures not just
  temperature changes (enthalpy of combustion)

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Recording mass of sodium carbonate

• Mass of weighing bottle Na2CO3 15.56 g
• Mass of weighing bottle traces 18.25 g
• Mass of Na2CO3 2.69 g
• Or an indication that the tare facility has been
  used

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Analysing

• Need to explain steps in calculations is a key
  area for development in some Centres
• Need to show how average titre is calculated from
  titrations
• Need to include sign in enthalpy of combustion
  calculations

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Analysing
Using v1c1 v2c2 without explanation is
unlikely to score full marks
Encourage correct use of significant figures
discourage my calculator reads 0.1246535, so
thats my answer
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Analysing

• In drawing conclusions from a titration
  candidates need to describe the outcome of
  calculations and not just assume that this is
  evident from numbers in a calculation

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Evaluating

• Comments on experimental procedure were often
  limited. This is a key area for development in
  many Centres
• Need to calculate uncertainties associated with
  one example of each type of measurement

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A2 Coursework 2855/01

• Individual Investigation

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Grade Boundaries

• Unchanged from last year
• Grade A 76 (38 out of 45)
• Grade E 44 (22 out of 45)

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Mark Changes As A Result Of Moderation

• 373 Centres marks unchanged
• 50 Centres marks reduced (12 of total)
• 1 Centre marks increased

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Mark Changes As A Result Of Moderation

• All Centres are allowed a tolerance before
  marks are changed
• Tolerance is or 3 out of 45
• Changes are made when the Centre marks are on
  average or 4 or more different from agreed
  moderation standard

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Mark Changes As A Result Of Moderation

• Changes recommended by moderators are usually
  applied to ALL candidates in the Centre

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Mark Changes As A Result Of Moderation June 2005
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Mark Scheme

• Centres need to check that they are using an
  up to date mark scheme

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Some Basic Issues

• Need to spend 15 to 20 hours on practical work
  (often equivalent to 3 to 4 weeks)
• Investigations needs to have a demand appropriate
  to an A2 assessment

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Nature of the investigation topic

• Too many students should not do exactly the same
  project.
• There is a tendency for some enzyme projects to
  be too biological which loses marks

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Nature of the investigation topic

• Students dont have to do a kinetics
  investigation!
• There are many other very suitable topics,
  particularly in physical chemistry

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Planning

• Starting with a hypothesis tends to lead to a
  superficial report. It is far better to write
  down precise aims.

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Planning

• The quality of risk assessments and references
  is a key area for development in many Centres,
  particularly in the use of Haz Cards and web
  addresses.

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Risk Assessments

• A risk assessment should be comprehensive,
  detailed and relevant

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References

• Encourage your students to
• consult a range of written sources
• include detail such as page number
• link the reference to the text

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Planning

• References to the internet should include a
  short description of the content of the web site
  as well as the web address

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Implementing

• Standards of recording should be at least what
  is expected in AS coursework. This is a key area
  for development in some Centres

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Implementing

• Documentation should be completed by the
  teacher during the practical sessions to help
  award a mark for manipulation. This should be
  sent to the moderator.

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Analysing

• Calculations need to be explained

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Analysing

• Conclusions tended to be descriptive rather
  than evaluative. This is a key area for
  development in some Centres

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Analysing

• Quantitative comparisons of data internally or
  with an external standard provides opportunity
  for comment on fine detail

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Evaluating

• Often the lowest scoring skill area
• Often treated in a mechanical way
• something to do to get marks
• rather than a genuine evaluation of both the
  procedure and the data

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Evaluating

• Need to look at uncertainty associated with
  all different types of measurement

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Evaluating

• Comments on limitations of experimental
  procedure were often superficial which reduced
  the overall mark. This is a key area for
  development in many Centres

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Evaluating

• Relative significance of uncertainties of
  measurements and limitations of experimental
  procedures was often not covered