Table & headings

Most tables were suitable. Issues: vague heading “test-tube” instead of “glucose concentration”; some included units inside the body of the table, losing full credit.

Conclusion vs trend

Many stated a suitable conclusion; a significant number described the trend instead of linking back to the stated aim.

Independent variable

Most identified concentration of glucose. Some incorrectly gave volume (too vague since final volume was standardised).

Control variable (with detail)

Temperature was common. Some answers lacked detail—e.g., “yeast kept constant” is insufficient; “volume of yeast kept constant” would gain credit.

Why stir the yeast suspension?

Few correct explanations. Step 5 had no glucose; stirring was to evenly distribute yeast cells, not to increase activity, and yeast does not “dissolve.”

Improvements to the investigation

Many suggested changes to steps that didn’t need improvement or proposed different investigations instead. Repetition was the most common valid idea.

Make 5.0 cm?3; of 0.25% glucose from 0.50%

Although some described it well, many couldn’t determine the correct dilution or make the specified volume.

Benedict’s test for glucose

Almost all knew the reagent and that heating is required. A few forgot “hot” water-bath or confused iodine–starch test.

Apparatus for collecting CO?

Gas syringe was the common correct choice. “Measuring cylinder” alone needed displacement/over-water detail.

What is an anomalous result?

Best description: a measurement that doesn’t fit the expected pattern. A few thought it means “inaccurate.”

Means with anomalies

Most knew to exclude the anomalous value. A few then divided by three instead of two.

Compare mean volumes (25 °C vs 35 °C)

Some produced detailed comparisons and manipulated data correctly; explanations were not required.

Graph quality & key

Mostly neat with labelled axes/plots/lines. Issues: extrapolating to origin, zero points missing, wrong time unit, cramped scale, wrong axis for independent variable, dashed-line keys (prefer markers).

Estimate time from graph

Most estimated correctly and indicated on graph; some marks were too small to show how the value was obtained.

Hydrogencarbonate indicator colour change

Few knew the correct colour change when CO? is bubbled through the solution.

Drawing cell X (bio drawing conventions)

Nearly all drew the single labelled cell with sharp pencil and continuous lines, no shading; many careful, detailed observations.

Actual length (3 s.f.)

Many correct calculations with answers to three significant figures.

Plan investigation: NaCl concentration & osmosis

Many strong plans using different NaCl concentrations; some confused concentration with volume or failed to standardise volumes. Common valid methods: measure mass/length before & after immersion for a set time. Frequent mistakes: measuring volume of solution before/after immersion, dialysis tubing with no plant tissue, confusing osmosis with transpiration (potometer/dye). Safety: goggles/gloves often unnecessary—most appropriate is safe knife use (cut away from body/on a hard flat surface).