Diffusion
Diffusion
- Diffusion is the net
movement of particles from a region of higher concentration to a region of
lower concentration down a concentration gradient as a result of their random movement.
- e.g. Diffusion in the alveoli as gaseous
exchange
Diffusion can be show in an experiment using Visking tubing:
- A Visking tubing bag full of starch solution is placed into a beaker of iodine solution.
- Iodine solution molecules go into the bag as there is
a higher concentration outside the bag
and they are smaller molecules.
- The starch molecules cannot get out of the bag as
they are too big.
- The Visking tubing slowly turns an orangey colour as
the iodine enters it.
- Partially permeable membrane: membranes
which only let some solute molecules
through.