2b: Movement of substances using visking tubing [2008]***

Template for answering diffusion question:

1. Compare: Compare Region of higher concentration and region of lower concentration

2. Direction: ___________ molecules diffuse from _______________ to __________________ by

3. Process: diffusion

From 2008 Practical Paper, diffusion of iodine molecules into the visking tubing containing starch solution

Time: 0 min

Time: 5 minutes

Time: 10 minutes

Final results after 15 minutes

In this case, note: iodine molecules are small enough and are able to pass through the partially permeable membrane of the Visking tubing.

However, the starch molecules are too large to pass through the Visking tubing.

Example of wrong set-up and thus inaccurate results

Wrong set-up vs Correct set-up

Process of diffusion: Iodine molecules diffusing into the Visking tubing filled with starch solution