Oscillating Chemical Reactions

Dieffenbaugher, Poteet 1

Clayton Poteet, Melissa Dieffenbaugher

Mr.McBride

Chemistry

9 November, 2011

Oscillating Chemical Reactions

Do you ever wonder what happens when you add different chemicals together? Well so did we. Except we decided to take it one step further. Oscillating chemical reactions is a chemical reaction that oscillates, or cycles, between different colors over a period of time. After doing research, we found that there are two main different kinds of oscillating chemical reactions. These two different types are Belousov–Zhabotinsky reaction and the Briggs-Rauscher reaction. Lets dig in a little deeper on both kinds of reactions.

The Belousov-Zhabotinsky reaction was the first chemical reaction to be found that has spatial and temporal oscillations. To do this experiment, you can find different kinds of “recipes” to show different kinds of colors, longer oscillation periods and brighter, more vibrant colors. We decided to use a concentration of different chemicals. This concentration includes malonic acid, manganous sulfate, potassium bromate and a sulfuric acid solution. After doing research we found that this reaction is going to cause an oscillation between blue and clear. The oscillation periods will last for approximately 30 seconds and will continue oscillating for over 30 minutes. Note that different chemical combinations could give you different results. The Belousov-Zhabotinsky reaction isn’t the only oscillating chemical reaction, however.

A different type of reaction, the Briggs-Rauscher reaction, was the first known homogeneous oscillting chemical reaction. The Briggs reaction is a good demonstration of the color changes, which starts as a colorless solution and formulates into an amber color, quickly changing to a very dark blue.

Dieffenbaugher, Poteet 2

After this process occurs, it slowly formulates back to a colorless solution repeating the color changing process approximately ten times. As the process begins to stop oscillating, the chemicals then end at a very dark blue color, smelling strongly of iodine. In this particular experiment the chemicals we use include, potassium iodate, distilled water, sulfuric acid, malonic acid, manganese sulfate monohydrate, and hydrogen peroxide. The mechanism of this reaction is quite complex, but the essential features of the system depend on two key processes. Process A is a “non-radical process,” which involves the intermediate production of an iodide ion. Process B is a “radical process,” which involves a quick auto-catalytic process using manganese and free radical intermediates. This process converts hydrogen peroxide and iodate to free iodine and oxygen. Process B can only occur at low concentrations of iodide. As you can see the two reactions are quite different.

Our main goal of this experiment is two find differences between the two reactions and how they are similar. Another question we are proposing is how can we make these oscillations occur at a faster rate with longer oscillating periods and, also, what catalystic chemicals we can find that can work for both reactions.

All of these scientists started off with a goal in mind much like us. We know what we have to accomplish and we have the tools to do so. Oscillating chemical reactions aren’t just a chemical reaction. They are science that appears right before your eyes. A reaction that not only changes color and odor, but a reaction that happens simultaneously without adding chemicals in between each phase, almost like a magic trick. In doing research I can’t find an experiment that demonstrates both of these reactions side by side with comparisons and data, but we are going to give it a try. Maybe they are to similar to be compared, maybe they aren’t. You never know until you try.