Science Experiment - Diffusion Through a Membrane

Iodine turns blue in reaction to starch. When a starch solution is placed in dialysis tubing (a semi-permeable membrane) and the tubing is added to a beaker of iodine , will the starch be able to pass through the tubing and turn the water blue or will the smaller iodine molecules pass through and turn the contents of the tube blue?

Category:

Education

Tags:

• science
• experiment
• diffusion

[aaronyanfan123]

@k1ngkung6 the iodine substance diffused into the bag because there is a higher concentration of iodine solution compared to the concentration of starch in the bag. Therefore, the starch turned blu in colour as starch reacts to iodine. Hope this helps! ^^

[Narzonia]

That looks like a condom

[TheSasBreeze]

does the iodine go into the dialysis tubing because of a lower concentration in the starch or because it can fit through the spaces in the tubing and then bonds to the starch which are too big to fit through the tubing? some links would be good too!!! thanks for the video! :)

[MrLembesis]

@aaronyanfan123 NO. The iodine diffused into the bag because iodine is small enough to pass through spaces in the tubing where as starch molecules are too large to fit through. If you reverse the experiment (put the iodine in the tubing and the starch on the outside) you will see the iodine once again pass through the tubing.

[TheMajorGator]

where were the starch molecules expected to move and why

[DarkAngelCullen]

Why Iodine..and not Bromine liquid?... ;D

[crazydude413968]

we did this in sciense but i forgot how so i googled it

[LMH1177]

horrible audio quality, i am quite disapionted in this outrageous video of science materials and i will not stand for this monstrosity which is this educational video apparatus.

[YMTEAARMHNJ]

@YMTEAARMHNJ

Once inside the bag, the iodine does not leave because it bonds to starch, which is too large a molecule to exit the bag through dialysis tubing pores. The bonding causes the color inside the bag to change. Remember: diffusion means that for any one solute, movement will occur down its concentration gradient - solute will go from areas of high to low concentration. Also keep in mind that molecules that are too big will not pass through pores that are smaller.

[YMTEAARMHNJ]

@aaronyanfan123

No, that's wrong. The iodine diffused into the bag because there is a higher concentration of iodine outside of the bag than the concentration of IODINE, not starch, within the bag. In fact, the bag contains no iodine potassium iodide at all to start off with! One may not apply a single case of high to low diffusion to two different solutes.

[Edeferent]

Thanks for the video.

A good follow up would have been to test the starch solution and the iodine and water solution with Benedict's reagent afterwards to test for the reducing sugar.