“This is an eye-catching colour change demonstration in which a colourless solution suddenly changes to a dark-blue after an amount of time. The demonstration is particularly well-suited as an introduction to reaction rates and kinetics.” (YouTube)
Alom Shaha gives a clear explanation of the Iodine Clock demonstration. It’s an awesome experiment, and if you’ve never seen it before, you’re in for a treat! What’s even more fascinating is that, although it appears instantaneous, the reaction actually starts off as thin tendrils in various parts of the beaker. This can be seen in the video after the break, showing the Iodine Clock reaction in slow motion (along with more explanation of what is going on).
Don’t blink. Onwards!