2C30.40 • Diffusion & Osmosis
Location: Cabinet 2
Equipment needed for preparation
Image of the black rings
Important: Professors MUST request twice in one week to see the difference in water levels. The difference cannot be seen in just one class period.
Equipment needed for preparation
Original amounts vs 24 hours later
Instructions/Notes:
- Day 1: show the class that the levels of both sides of tube are equal.
- Day 2: show the class that after 2 days, the levels of the tubes have changed, with a higher level being on the solution side
Demo Staff:
- Make sure to SOAK the semi-permeable membrane in a beaker of distilled water for at least 30 minutes before setting up. This removes the preservative from its surface. The water level should cover at least the entire membrane.
- While the membrane is soaking, prepare the sugar solution.
- Measure out 27.4 g of sugar onto the scale. Mixing this into 40 mL of distilled water will create a 2 M sucrose solution. Ensure all sugar granules have dissolved.
- After the membrane is done soaking, place it between the two tubes, ensuring the membrane is secure. There are holes on the membrane which you hook onto the pegs.
- Mark off the levels of the solution using colored tape to clearly see the difference after a few days.
- Make sure the black rings are in place. The apparatus will leak if they are not there.
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Preparation of the solution
Image of the black rings
Concepts Conveyed:
- Osmosis; water from a low concentration solution will always move to a solution with high concentration if possible. The sugar solution has a higher concentration compared to the distilled water.
- The semi-permeable membrane allows for the movement of water, but not the movement of particles.
Last updated on March 11, 2025