Can Pure Carbon Substitute for Starch in the Iodine-Water Clock Reaction?

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Discussion Overview

The discussion revolves around the potential substitution of pure carbon for starch in the iodine-water clock reaction, exploring the chemical properties of starch and its role in the experiment.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions whether pure carbon can substitute for starch in the iodine-water clock reaction, noting that starch is essentially carbon.
  • Another participant clarifies that starch is a carbohydrate, not pure carbon.
  • A participant shares their successful experience using pure starch and expresses doubts about the necessity of hydrogen and oxygen in starch for the reaction, suggesting that these components may not be essential due to the presence of water.
  • Another reply asserts that the hydrogen and oxygen components of starch are essential for the reaction, emphasizing the difference between a compound containing carbon, hydrogen, and oxygen and a mixture of these elements.
  • A participant explains the structural formula of carbohydrates, indicating that while they may appear to be composed of carbon and water, this is a result of the valencies of the atoms involved.

Areas of Agreement / Disagreement

Participants express disagreement regarding the necessity of hydrogen and oxygen in starch for the iodine-water clock reaction, with some asserting their essential role while others question this requirement.

Contextual Notes

There are unresolved assumptions regarding the chemical properties of starch and the implications of substituting pure carbon, as well as the specific requirements for the iodine-water clock reaction.

minus459.67
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I've been teaching my daughter about the elements and am demonstrating the iodine+water+starch="clock" reaction. In an effort to provide accurate and straightforward information I am wondering that since starch is essentially carbon if pure carbon can be substituted for starch or if the starch has some property essential to the outcome of the experiment?

- Thanks
 
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Borek said:
Starch is not carbon, it is a carbohydrate.

Thanks for the response. We used pure starch and were successful. We learned the carbohydrates in starch were made up of carbon hydrogen and oxygen. My original idea was that since the experiment included water anyways that the hydrogen and oxygen components of the starch carbohydrate wouldn't necessarily be essential. Although I never tested this hypothesis I have doubts it would work.
 
minus459.67 said:
My original idea was that since the experiment included water anyways that the hydrogen and oxygen components of the starch carbohydrate wouldn't necessarily be essential.

They are essential. There is a huge difference between a compound that contains carbon, hydrogen and oxygen, and mixture containing all three elements.

Most (but not all) carbohydrates have formula Cm(H2O)n - that is, they look like made of carbon and water, But it doesn't mean they are made this way, it is just a side effect of the valencies of atoms involved.
 

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