In a chemistry class experiment, iodine can react with certain compounds, particularly those containing starch or some types of metals. Here's how some common white powder items might interact with iodine:
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Starch: Starch is the most notable white powder that reacts with iodine. When iodine is added to a starch solution, it forms a blue-black complex due to the formation of a helical structure around the iodine molecules. This is a classic demonstration in chemistry.
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Sodium Bicarbonate (Baking Soda): Sodium bicarbonate does not react with iodine in a way that causes a color change, but it can be tested as a control to compare against starch.
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Calcium Carbonate: Similar to sodium bicarbonate, calcium carbonate (found in chalk) does not typically change color with iodine.
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Talc: Talc is primarily a silicate and will not react with iodine to cause a color change.
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Sugar (Sucrose): Sugar (in its pure form) does not react visibly with iodine.
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Flour: If flour has a significant amount of starch in it, it may show a blue-black color change when iodine is added.
In summary, the most notable white powder that will result in a clear color change with iodine is starch. If you're experimenting with other powders, they may not invoke the same response, and starch is ideal for observing this characteristic iodine reaction.