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GCSE Biology · key term
The difference between the initial and final values of a measured quantity, taken in the appropriate direction; for example, substrate used is initial amount minus final amount.
Used by Edexcel
Specification 1.11, 9.19B · Paper 1, Paper 2
Revise: Rate CalculationsIt might be the mass of substrate used, the volume of product formed or a change in concentration. It is not normally a change in the amount of enzyme: an enzyme acts as a catalyst and is not used up by the reaction.
The difference between the final and initial values of a quantity; it may be positive or negative.
Make sure the change and time use the units requested. Convert the time before dividing if necessary.
When reading a graph, use the change in the measured quantity—not simply its final value.
When comparing rates, distinguish an absolute change in rate from a percentage change in rate.
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