Waec Model Questions Vol1 2025 Biology Question 3

A group of students conducted an experiment to investigate the effect of varying concentrations of a sugar solution on the rate of osmosis in potato cells. They prepared five different concentrations of sugar solution (0%, 5%, 10%, 15%, and 20%) and cut equal-sized potato cylinders, measuring 5 cm in length and 1 cm in diameter. After immersing the potato cylinders in the solutions for 30 minutes, they measured the final mass of each potato cylinder. The results are recorded in the table below: | Concentration (%) | Initial Mass (g) | Final Mass (g) | |-------------------|------------------|----------------| | 0 | 20 | 22 | | 5 | 20 | 21 | | 10 | 20 | 20 | | 15 | 20 | 18 | | 20 | 20 | 16 | (a) Calculate the percentage change in mass for each concentration of sugar solution. (b) Based on your calculations, explain how the concentration of the sugar solution affects the rate of osmosis in potato cells. (c) Discuss two potential sources of error in this experiment and suggest how these can be minimized.