IB Biology SL C1.2.6 Variables Affecting Rate Questions

mass of sucrose

OR

grams of sucrose;

Marking guidance:

Do not accept amount, quantity or sucrose alone.

a. to ensure time for yeast respiration/fermentation/metabolism/enzyme/reaction to start;

b. to allow sucrose to mix/dissolve;

c. temperature to stabilise;

d. to allow sucrose uptake by yeast;

e. to displace air with carbon dioxide;

Marking guidance:

Do not allow 'to use up the oxygen' .

1 max

a. (yeast) enzymes require an optimum/suitable temperature to work OR

named enzyme requires an optimum/suitable temperature to work require an optimum/suitable temperature to work;

b. it must be a controlled variable

OR

the change in carbon dioxide volume is only due to mass of sucrose OR

so the change in carbon dioxide is not affected by temperature change;

c. if temperature is too high, enzymes would denature;

b. OWTTE

c. OWTTE

1 max

a. higher masses of sucrose prevent respiration/fermentation;
b. higher mass (of sucrose), less volume (of $\mathrm{CO}_{2}$ ) produced;
c. negative relationship between sucrose mass and respiration;
OWTTE
1 max

Candidate gives modification for 1 mark and 1 mark for reason. The reason must match the modification.
a. include a control of $0 \mathrm{~g} /$ without sucrose;
b. to compare other results;
OR
c. use more masses of sucrose;
d. to get intermediate values;
OR
e. more trials/samples/replicates;
f. to increase reliability / take mean/average / identify outliers/anomalies / enable statistical analysis / example of statistical analysis;
OR
g. use a different method to measure carbon dioxide;
h. to avoid errors in measuring gas volume (with balloons);
g and h. may be with an example
such as. collect gas under water using
measuring cylinder, use a gas pressure sensor;
syringe. airlock, respirometer or by
measuring the pH .
2 max