This demonstration is called the chemical traffic light and this is a solution of sodium hydroxide and dextrose with an indigo carmine indicator. So as you can see at the start this is a yellow solution but when I give the bottle a shake we introduce oxygen into the mixture. That oxygen oxidizes the indigo carmine turning at green. As the reaction proceeds you can see the color changes to red. This is a transition state. As the oxygen begins to get consumed and then we proceed from red back to the reduced state of indigo carmine back to the yellow color. So just a pretty straightforward demo the chemical traffic light.