Osmosis required practical

Question 1

Method for potato osmosis experiment

Answer 1

• Cut out identical cylinders of potato using a ruler and measure the mass of each.
• Put one into a beaker of pure water and the other into a beaker of 1 mol?dm3 sugar solution.
• put some potatoes in a beakers with 0.2M conc
• Leave the potato cylinders in the in each beaker for around 24 hours. Take them out after 24 hours and dry them with a paper towel; then measure the new mass of each.
• If the mass has increased, water has been drawn in via osmosis. If the mass has decreased, water has been drawn out via osmosis.

Question 2

Why calculate the mass?

Answer 2

• To better compare the effect of sugar concentration of the cylinders that didn’t have the same initial mass. (Increase in mass = positive percentage change, decrease in mass = negative percentage change)

Question 3

Dependant, indépendant and control variables

Answer 3

Dependent - Potato mass
Independent - Concentration of the sugar solution
Control - Volume of solution, temperature, time, type of sugar used, species of potato

Question 4

Cause of error and how to reduce effect of errors

Answer 4

• Some of the potato cylinders not being fully dried (excess water would increase the mass)
• Water evaporating from the beakers (the concentrations of the sugar solutions would change

These errors can be avoided by repeating the experiment and calculating a mean percentage at each concentration