Science Buddies: "Ask an Expert"

We conducted the experiment for a science fair project with seven different salts. Initially several of the results looked very similar. However after three days, the iodide content coloration greatly changed and deminished in several of the samples. Conditions in the room did not change and the samples were in the same environment. Why did these changes occur an what caused this to occur? Thanks for answering,

Hi,

In the standard version of this experiment, you should only record the immediate/early color changes. The reaction between iodine and starch and resulting color change should happen very quickly, showing you which salts have added iodine within a few seconds or minutes.

I'm not sure what might be happening over a longer time scale- the iodine-starch complex is probably breaking down somehow, perhaps due to heat, random motion of the molecules in the system, some sort of contaminating enzyme that degrades starch, etc.

Megan