1.16 - Core Practical - Osmosis in Potatoes and 1.17 - Percentage Gain and Loss of Mass Flashcards
What is a useful example to measure percentage gain or loss of mass?
Potato disks.
What is the first step in the method for measuring mass change in potato disks?
Cut potato into small discs of equal size (e.g 2cm diameter).
What should you do after cutting the potato disks?
Blot the potato disks gently with tissue paper to remove excess water.
What is the next step after blotting the potato disks?
Measure the initial mass of each disk.
What should you do with the disks after measuring their initial mass?
Place the disks in sucrose solutions of different concentrations (1%, 2% etc).
What should you do after placing the disks in sucrose solutions?
Blot with tissue paper again and record new mass.
How do you calculate the percentage gain or loss of mass?
Find difference in mass (end mass - start mass) and use the percentage change equation: (change in mass / start mass) x 100.
What is the independent variable in this experiment?
The concentration of the sucrose solution.
What is the dependent variable in this experiment?
The change in mass of the potato disks.
What is the control variable in this experiment?
The diameter of the disks (2cm).
What is happening in this experiment?
Water is moving by osmosis from a more dilute solution (in the potato) to a more concentrated solution (the sucrose solution) across a selectively permeable membrane.
