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Home science lab... can anyone explain this?

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We are doing an in-home science experiment that is a chemical reaction. It is easy to do and inexpensive, but I am lacking knowledge as to WHY this happens... and WHAT it has to offer us (educational value? fun? pique ones interest in chemistry?) or the world (any higher purpose?).


Help would be very appreciated!!!!


Here is the website for it: http://www.sciencebob.com/experiments/iodine_clock_reaction.php


To quote the page:

..."basically it is a battle of chemistry between the starch which is trying to turn the iodine blue, and the Vitamin C which is keeping it from turning blue. Eventually the Vitamin C loses and, bam! - you get instant blueness. "


Our question: why is the starch trying to turn the iodine blue?? Why does the vitamin c keep it from turning, at least initially?


We're using this for a science fair.... just thought some of you might have insight or know how to explain it...


And, it's fun if you want something "sciencey" to do!

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Vitamin C reduces iodine to iodide and only once the vitamin c is exhausted (used to convert) will you then see the reaction of the iodine and starch. Iodine reacts with many substances as it is very powerful oxidant. In the mixture of different substances it first reacts with molecules that easier to break down. Vitamin C is anti-oxidant and will react with Iodine promptly. Basically you're playing around with a vitamin c titration protocol - if you google it, you can probably find more meaningful things to add to the basic experiment and make it more in-depth.

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Well... my son learned a lot about the scientific method! His hypothesis was that a higher temperature of water would speed up the time for the chemical reaction to take place... and that extra vitamin c would also speed up the chemical reaction. Half of that was true, the other half false!


Our first run, water temp. was 100 degrees and it took 4 minutes for the chemical reaction to take place (for this example that means that it took 4 minutes for the solution to turn dark).


The second run our water temp was 150 degrees and it took 40 seconds for the water to turn dark!! (I did time lapse photos... every 10 seconds).


For the third run, we doubled the vitamin c, which made it fight harder to keep the iodine from turning and we kept the water temp at 150 degrees. That time it took 1-1/2 minutes.


Now we are going to continue learning about the properties of our characters and put it all together in a presentation...

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