Required practical 3 - Osmosis

Question 1

What is osmosis?

Answer 1

The movement of water from an area of high concentration to an area of low concentration through a partially permeable membrane.

Question 2

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

Answer 2

• Cut identical potato cylinders using a cork borer.
• Measure and record the length and mass of cylinders using ruler and balance/scales.
• Add each cylinder to one of 3 solutions : 1M sugar solution, 0.5M sugar solution and distilled water.
• Leave cylinder in tubers overnight.
• Record length and mass of each cylinder.
• Draw graph of change in mass in grams (y axis) against concentration of solution in mol/dm^-3 (x axis).

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.