Edexcel IAL Biology 3P.6 Variables and controls

Name the changed factor and measured response from the question, then pair every confounder with a feasible method such as an incubator, buffer or fixed volume.

Exam points

State independent and dependent variables precisely from the investigation context.
Match each controlled variable to a practical method that keeps it constant.
Explain how control or solvent-only treatments isolate the tested factor's effect.

[Maximum number: 2]

The enzyme invertase breaks down sucrose into its two component monosaccharides.

(a)

The effect of pH on the initial rate of the reaction catalysed by invertase was investigated at $25^{\circ} \mathrm{C}$ .

State the independent variable in this investigation.

[ 1 ]

(b)

Name one non-biological (abiotic) variable, other than temperature, that should be kept constant in this investigation.

[ 1 ]

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3P.6—Variables and controls question 1

Question (a)

Question (b)