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Flashcards · Biology · Transport In and Out of Cells

Investigating Osmosis in Plant Tissue

23 cards

  1. What is the aim of the osmosis practical?

    To investigate the effect of different concentrations of salt or sugar solution on the mass of plant tissue.

  2. Why is potato used?

    It is cheap, easy to cut into identical pieces, and made of cells with partially permeable membranes.

  3. What tool cuts potato cylinders of equal width?

    A cork borer.

  4. What is the independent variable?

    The concentration of the solution.

  5. What is the dependent variable?

    The percentage change in mass of the potato.

  6. Name three control variables.

    The size of the cylinders, the volume of solution, the time in solution (also the temperature and the type of potato).

  7. Why do you blot the cylinders dry before weighing?

    To remove liquid from the surface, which would add extra mass.

  8. What is the formula for percentage change in mass?

    (final mass − start mass) ÷ start mass × 100.

  9. A cylinder goes from 2.00 g to 2.30 g. What is the percentage change?

    +15%.

  10. What does a negative percentage change mean?

    The potato lost mass, because water left it by osmosis.

  11. Why use percentage change and not just change in mass?

    The cylinders start with slightly different masses, and percentages make the results fair to compare.

  12. What does a gain in mass tell you about the solution?

    It is more dilute than the potato cell sap.

  13. What does a loss in mass tell you about the solution?

    It is more concentrated than the potato cell sap.

  14. What does it mean when the graph line crosses zero?

    There is no change in mass, so the solution has the same concentration as the cell sap.

  15. How do you find the concentration of the cell sap from the graph?

    Read the concentration where the line crosses 0% change.

  16. Why use pure water as one of the solutions?

    It is the most dilute solution, and shows the most water entering the potato.

  17. How can you make the results more reliable?

    Repeat the test with several cylinders and calculate a mean.

  18. What is an anomalous result?

    A result that does not fit the pattern of the others.

  19. How could you find the cell sap concentration more accurately?

    Use extra solutions of concentrations close to where the line crosses zero.

  20. Give one safety precaution.

    Cut on a tile, with the blade pointing away from your hands.

  21. Six numbered pictures of the steps of the potato investigation, with no captions. Describe the six steps of the potato osmosis investigation. The six steps of the investigation, each described.

  22. A falling curve of percentage change in mass against concentration with no marks showing where it crosses zero. Read the concentration of the potato cell sap from this graph. The graph with the zero crossing at about 0.33 marked.

    About 0.33 mol/dm³: where the line crosses 0% change, so there is no net movement of water.

  23. A cylinder goes from 3.20 g to 2.72 g. What is the percentage change in mass?

    −15%. The change is 2.72 − 3.20 = −0.48 g, then −0.48 ÷ 3.20 × 100 = −15%.