This YouTuber created a "chemical clock" by making a substance that changes colour over time.

Two solutions are mixed to create the colour-changing substance.

One of the mixtures is composed of warm water, corn starch, and hydrogen peroxide and the other is made from vitamin C powder, cold water, and iodine aqueous solution.

In this video, I try to create a so-called iodine clock using chemical reactions. It involves mixing two solutions and, as a result of a chemical reaction, after some time the color of the resulting substance changes irreversibly.

To prepare the first substance you need:
warm water, corn starch, hydrogen peroxide.
to prepare the second one:
vitamin C powder, cold water, iodine aqueous solution, cold water.