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Copy of Iodine Clock Reaction

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Melinda Batista

on 3 April 2014

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Transcript of Copy of Iodine Clock Reaction

Melinda Batista
Mrs. White
Period 5-6


Color Changing



My Hypothesis
What Got Me Interested...
Mixing sodium metabisulfite, concentrated sulfuric acid and ethanol with boiled water and soluble starch and then adding that to potassium iodate will make the electrons within the solution interact with the starch and result in the color change of a black liquid
A chemical reaction MUST occur for the color of the mixture to change
It is possible to speed up the reaction by manipulation of the chemicals
There is multiple reactions within one experiment

Independent Variable: The amount of chemicals used

Dependent Variable: How fast the liquid turns blue


The specific chemicals used (sodium metabisulfite, sulfuric acid, etc.)
Research Question
If I add sodium metabisulfite, sulfuric acid and ethanol to boiled water and soluble starch, then add potassium iodate and distilled water to the mixture, would it change color? If so, is it possible to control the speed of this reaction and how can one single chemical reaction make that unbelievable change of color?

Watch the liquids VERY closely or else you'll miss it!

1 250 ml beaker
2 100 ml beakers
2 1000 ml beakers or flasks
1.2 g sodium metabisulfite
10 ml ethanol
4 g concentrated sulfuric acid
4.3 g potassium iodate
2 g soluble starch
distilled water
Solution A: In 1 liter of distilled water, add 1.2 g of sodium metabisulfite. After that, add 4 g of concentrated sulfuric acid with care, and then add 10 ml of ethanol
Solution B: Add 4.3 g of potassium iodate to 1000 ml of distilled water
Solution C: Boil water and measure out 50 ml. Then add 2 g of soluble starch and allow to cool
In a 250 ml beaker, combine 50 ml of Solution A with 50 ml of distilled water. Then add 10 ml of solution C to the mixture
In a 100 ml beaker, combine 50 ml of Solution B and 50 ml of distilled water
Get stopwatches ready!
Pour the solution in the second beaker into the first beaker, and continue to pour back and forth for 8-10 seconds
Watch how the combined solutions transition from clear liquids to an ink color instantly!
Chemistry Interpretation:
First, bisulfite ions (HSO3-) reduce some of the iodate ions (IO3-) to form iodide ions (I-)

Next, the iodide ions (I-) are oxidized by the remaining iodate ions (IO3-) to form triiodide ions (I3-). The solution now consists of triiodide ions (I3-) and soluble starch

After that, the triiodide ions (I3-) get reduced by the bisulfite ions (HSO3-) to become iodide ions (I-); which continues until all of the bisulfite has been used

Lastly, the triiodide ions and the starch combine to form the dark blue/black starch complex.
The Heart of the Reaction:
triiodide ions (I3-), which is 3 Iodine atoms with a negative charge, interact with starch to create the instant ink color
This reaction is referred to as the Landolt Clock Reaction (discovered by Hans Heinrich Landolt in 1866). When you prepare the Solutions A, B and C, the chemicals begin to mix and form new chemical compounds which is a very slow reaction and not visible to the naked eye. When you begin to pour the solutions together, a much faster reaction occurs, leading to the final reaction which is instant. The clear liquid turns into a jet black/blue iodine-starch complex. These reactions happen at different intervals because the individual chemicals react at specific speeds and can be manipulated to occur at certain times as well. The reverse reaction is undoing what just occurred with additional starch added to the mixture, and then resumes to its original state.
How Does it Work: Synopsis of My Research
My hypothesis was both

How I was
My hypothesis was surprisingly accurate. After watching the video, I knew that the electrons in the chemicals would react with starch and produce a significant reaction for being the overall different component within this experiment. I knew from the beginning that an experiment with so many chemicals would be unlikely to just have a single reaction and produce the result that it did; so I hypothesized correctly by saying there was more than one reaction within this experiment. In addition, It is indeed possible to control the speed of the reaction. If you manipulate the concentration of the chemicals like potassium iodate and metabisulfite, the reaction will take place within a certain time. All in all, I hypothesized correctly.

How I was
Watching the video, I hypothesized that this experiment's result was a black liquid, but it really is a dark blue that appears like black liquid; so I was wrong in that aspect.

My Conclusion
This experiment should only be done with the help of an adult. Iodine will stain anything it touches and can be very hazardous. Safety goggles as well as other chemical protection is needed throughout the experiment. This is the most important step of all; protection is key.
Is It REAL?!
Of course it's real! This chemical reaction is undeniably possible. The reaction on tape speaks for itself with it's step by step process and the multiple ways of presenting the reaction which is done on purpose to prove my point exactly. Not to mention Steve Spangler himself, who is a science author, famous for his mentos geyser experiment on YouTube among other things, was conducting multiple clock reactions on live national television and in front of an audience. I provided evidence by going in depth with the synopsis of my research as well as a chemical interpretation which explained why the ions reacted with the starch to create the dark blue liquid. Also, The color change is an obvious indication that a chemical reaction has occurred, and the experiment itself is called a "clock reaction" because it means you can change the amount of time it takes for the liquids to turn blue. Furthermore, the Iodine Clock Reaction is quite possible.
Reverse Reaction:
By adding starch to the mixture already created and then stirring, it acts as an opposite reaction in which the dark colored liquid becomes clear again, then returns to the experimental state of an opaque liquid. The rate of the forward action is equivalent to the rate of the reverse action.
Classic, simple and multiple variations of this experiment, the Iodine Clock Reaction was very interesting to research about.
I hope you all learned something today!
The End
Clean Up!
- Pour all liquids down the drain carefully with plenty of water
- Wash your hands well
- Recycle
- Dispose other materials in the trash
Full transcript