Practical: Diffusion and Osmosis

Question 1

What is osmosis?

Answer 1

The movement of water molecules from a higher water potential to a lower water potential through a partially permeable membrane.

Question 2

Describe how you would carry out an investigation into osmosis using potato tissue

Answer 2

Question 3

Why is it necessary to use a cork borer to cut the cylinders?

Answer 3

Results in equal sized samples so changes in length and mass can be compared easily

Question 4

Why is it necessary to blot the cylinders with paper after removing them?

Answer 4

Each cylinder may have a different amount of water on its surface, so masses may vary. Blotting cylinders allows masses to be comparable

Question 5

What safety precautions should be taken with this experiment?

Answer 5

Handle cork borer and scalpel with care

Question 6

How can the water potential of the plant cells be found?

Answer 6

Plot a graph of change in mass against concentration.
Find the x-intercept, which is the concentration of solution that is isotonic to the plant cells.

Question 7

State a source of error in this practical.

Answer 7

Plant tissue taken from different parts of the plant may have different water potentials.

Question 8

What equipment can be used to investigate osmosis in non-living systems?

Answer 8

Using a capillary tube inserted into a visking tubing, placed in a beaker of solution.

Question 9

What indicates osmosis in the non-living system?

Answer 9

The change in water level in the capillary tube.

Question 10

What is the change in water level when the visking tube filled with water is placed in sucrose solution?

Answer 10

Water level drops and water moves out of the visking tube by osmosis.

Question 11

What is the change in water level when the visking tube filled with sucrose solution is placed in water?

Answer 11

Water level rises and water moves into the visking tube by osmosis.