Iodine and Starch Experiment | Iodine Experiment | Starch Experiment | Science experiments for kids

Iodine and Starch Experiment | Iodine Experiment | Starch Experiment | Science experiments for kids

Simple and easy experiment to demonstrate the iodine with starch reaction!

For this test you will need:
• Two test tubes
• Soluble starch powder
• Iodine solution
• Water
• Dropper
• Put some starch powder into a test tube and fill the test tube with water.
• Mix the starch in the test tube well until the starch dissolves in the water.
• Fill the other test tube with normal water.
• Place both the test tubes in a test tube stand.
• Using a dropper take iodine solution.
• Put some drops in each test tube.
• Observe that the test tube with starch solution turns to purple black color.
• The other test tube with normal water retains the color of iodine i.e orange or yellow.
Starch is a mixture of amylose and amylopectin, which are different forms of glucose/starch.
Amylose in starch is responsible for the formation of a deep blue black color.
Amylase is long polymer chains of glucose units connected by an alpha acetal linkage and looks much like a coiled spring.
However iodine is a potassium iodide reagent and it is not very soluble in water.
So, iodine is prepared by dissolving it in water in an aqueous solution of potassium iodide. This results in a linear tri-iodide ion (I3−) complex in iodine which is soluble.
This tri-iodide ion (I3−) slips into the coil of the starch causing an intense or deep blue-black color.


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  1. Where can I buy the iodine for this? I bought some iodine at drug store, but it is clear and is not working with the corn starch to turn blue. Desperate to figure this out!

  2. i don't think a kid can understand all the Amylose thing.. lol
    So, when we add Amylase to the iodine and starch, will it be digested and color will change from blue to yellow again?

  3. obviously the narrator has no idea what he's talking about. reagent is pronounced ree-ay-jent, and the I3- ion is a complex ion, not "complex". it doesn't mean anything when he says that "iodine is a potassium iodide reagent," because obviously iodine is in potassium iodide (based on the name) but iodine is not solely involved in reactions as a reagent to form potassium iodide. the rest is okay, but don't rely on the video's explanation for the color change too much. 

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