Cambridge Pre-U Syllabus - Cambridge International Examinations

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Cambridge Pre-U Draft
Candidates should be able to explain how to make up solutions:
in % (w/v), e.g. by adding a known mass of solute to a small volume of solvent, mixing until fully
dissolved and then making up to the final volume with solvent;
in mol dm –3 , by dissolving the molar mass of solute and then making up to 1 dm 3 with solvent;
by using serial dilution to make up a wide range of dilutions, e.g. by factors of 2 or 10;
by proportional dilution in order to make up a narrow range of dilutions.
Candidates should be able to carry out a simple risk assessment of their planned investigation, identifying
the areas where accident or injury is most likely and would be most serious. They should be able to use this
to propose appropriate safety precautions specifically related to the risks that they have identified – e.g. they
might identify that protease enzyme solutions pose a particular risk to the cornea if they are splashed, and
that therefore the wearing of eye protection would be an appropriate precaution.
Candidates should be able to describe the main steps that they would use in order to get to the point of
being able to draw conclusions, including, as appropriate, preparation of results tables, proposed graphs to
plot, key points to consider in any evaluation of the method and results, and reference back to the
hypothesis.
Sub-skill
Determining number of measurements and/or observations to take
Candidate should be able to:
• choose a suitable range of values for the independent variable in an investigation;
• choose a suitable number of intermediate values for the independent variable;
• decide how many replicates to take of each value of the independent variable to ensure reliability
(reproducibility) of results;
• decide how many observations to take in an investigation that generates qualitative data.
Candidates should apply their knowledge and understanding of methods of analysis and evaluation to
ensure that they plan to take enough readings of the independent variable to be able to draw a graph and/or
make valid conclusions. They should also be aware of the variability of results in biological investigations so
that they plan to take enough replicates to carry out a statistical analysis (see Notes on the uses of
statistics in biology below).