Course Content
NUTRITION IN PLANTS AND ANIMALS
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Biology Form 1
About Lesson

Practical activity: To demonstrate osmosis using a visking tube

Requirements

  • Visking tube- is a synthetic semi-permeable material.
  • Ruler
  • Thread
  • 20 sugar solution
  • Beaker containing distilled water
  • Glass rod

Procedure

  1. Obtain an 8 cm long visking tube. Rub it under water to open it.
  2. Tightly tie one end of the tube with a thread
  3. Half fill the visking tube with 20% sugar solution.
  4. Tie the other end ensuring there is no leakage.
  5. Immerse the visking tube into a beaker containing distilled water as shown below.
  6. Let the set-up stand for two hours

 

Observation

It will be noted that the sugar solution would increase in volume making the visking tube become swollen.

Explanation.

The sugar solution was hypertonic to distilled water hence water molecules moved from the beaker into the visking tube by osmosis. This increases the sugar solution with the visking tube becoming swollen.

If the visking tube was filled with distilled water and then immersed in a beaker containing 20% sugar solution, water molecules move out of the visking tubing into the beaker since the sugar solution is hypertonic to distilled water inside the visking tube. The volume of water in the visking tube would reduce and visking tube would shrink.

 

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