Universe of Science Chemistry Kits: Presto! Clock Reaction Kit. I have to tell you about these great kits. What a great way to reinforce what they're learning in chemistry! Each kit comes in a plastic tub and contains the “ingredients” for as many as 15 experiments in one tub! They give you enough ingredients to repeat the experiments over and over as well (which my kids really enjoyed). Each kit also comes with a booklet (approximately 25 pages long) with step-by-step instructions, as well as science definitions, explanations of the chemical reactions, and further instructions for how to use household ingredients to do even more experiments! You really get a lot for your money. In fact, I thought these would be your typical do-it-just-once-and-and-kiss-your-money-goodbye type kits, but that’s not what we got! I wish I had room to show you all the pictures I took of the kids playing with these. I tried them on all my kids (ages 8-15), but only the older ones understood the science behind the experiments. The younger ones just enjoyed playing. (Some ingredients may be allergens.) With this particular kit you can make 2 chemical solutions and mix them together. Wait a few seconds, then wow! It will suddenly change colors. This is the famous iodine clock reaction in an easy to use kit. Change the concentrations or temperature and change the times for the color change. do the clock reaction with Eco-foam. Learn about solutions and rates of reaction (kinetics). Contains starch solution, sodium iodate, sodium sulfite, citric acid, sodium thiosulfate, eco foam, stirrers, scoop, spoon, baggies, cups, and chemistry booklet with many experiments and enough "stuff" to do the experiments numerous times! All at such a low price! Buy all 6 and Save! Retails @ $9.00 Our Price $7.65