Science Practical 17

Moving Waters(Teacher's Demo)

Aim: To demonstrate the process of Osmosis

Apparatus:

Beaker (400cm cube)

Capillary Tube (30cm long)

Retort Stand

Visking Tubing (15cm, knotted at one end)

String

50% Sucrose Solution

Marker Pen

Procedure:

1. Soak the visking tubing in water for 2 minutes. Remove when it becomes soft and pliable.

2. Clamp the capillary tube to the retort stand.

3. Pour the sucrose solution into the visking tubing until about 3cm from the top.

4. Place the visking tubing below the capillary tube. Move the visking tubing up so that the capillary tube is about 1cm into the sucrose solution.

5. Tie the open end of the visking tubing tightly using the string.

6. Rinse the outside of the visking tubing by dipping it into a beaker of tap water. then lower the tubing into a fresk beaker of water.

7. Mark the level of sucrose solution in the capillary tube. This is the level of sucrose solution at the start of the experiment.

8. Observe and mark the level of the sucrose solution at intervals of five minutes for about 90 minutes.

Conclusion:

Osmosis is a net movement of water molecules from a region of high water potential to a region of low water potential through a semi-permeable membrane.