1. Why use a calibration curve?
Specification: 3.1.2 / 3.6.4.2 · Colorimetry and RP11 connection
AQA required practical 11 involves producing a glucose dilution series, using a colorimetric technique to construct a calibration curve, and estimating glucose concentration in an unknown model urine sample. It is a required practical in the full A-level course, even though the underpinning carbohydrate chemistry is taught in Year 12.
This is different from making a rough colour judgement after Benedict's test. A calibrated measurement links an instrument signal to known concentrations under a specified and validated experimental method.