It's still very difficult to find a picture of this. I remember that there is a pattern diagram of this in my college advanced organic book, but it's more troublesome to get it down. Let me talk about the principle:

Starch turns blue when it meets iodine, which mainly depends on the structure of starch itself. Starch is a white amorphous powder, consisting of amylose (accounting for10-30%) and amylopectin (accounting for 70-90%). Amylose can be dissolved in hot water without being mushy, while amylopectin is insoluble in water, and it will swell into mushy when hot water acts on it. Among them, amylose, which is dissolved in water, is in a curved form and curled into a spiral shape by intramolecular hydrogen bonds. At this time, iodine is added, in which iodine molecules drill into the gap in the spiral and are linked with amylose by van der Waals force, thus forming a complex. This complex can absorb other visible light except blue light (wavelength range is 400-750 nm) evenly, thus making starch dark blue.

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Explaining why starch turns blue when it meets iodine with molecules mainly depends on the structure of starch itself. Starch is a white amorphous powder, consisting of amylose (accounting for10-30%) and amylopectin (accounting for 70-90%). Amylose can be dissolved in hot water without being mushy, while amylopectin is insoluble in water, and it will swell into mushy when hot water acts on it. Among them, amylose, which is dissolved in water, is in a curved form and curled into a spiral shape by intramolecular hydrogen bonds. At this time, iodine is added, in which iodine molecules drill into the gap in the spiral and are linked with amylose by van der Waals force, thus forming a complex. This complex can absorb other visible light except blue light (wavelength range is 400-750 nm) evenly, thus making starch dark blue.

Iodine and starch will turn blue-purple. When cooking, add raw flour and salt. Why not turn blue-purple? Iodine turns blue when it meets starch.

Iodine in salt exists in the form of iodized salt (such as potassium iodate), and there is no iodine!

Iodine wine is a mixture of iodine, potassium iodide and ethanol, and there is iodine in it!

Why doesn't starch turn blue when added with saliva and iodine? Because saliva amylase hydrolyzes starch into maltose, iodine turns blue only when it meets starch.

This phenomenon tells us that there is amylase in saliva, which can break down starch.

Iodine has the function of sterilization, iodine will turn blue when it meets starch, so does iodine after reacting with starch still have the function of sterilization? Iodine in iodine wine has strong oxidation, and it will turn blue when it meets starch. After reacting with starch, iodine wine loses its sterilization effect!

Starch will turn blue when it meets iodine, and it will change color when it meets anything. It can be used as magic writing. Purple litmus turns red when it meets acid (hydrochloric acid and sulfuric acid) and blue when it meets alkali (lime water and potassium hydroxide). Or carbon dioxide will turn red (water+carbon dioxide = carbonic acid)

Phenolphthalein turns red when it meets alkali (lime water, potassium hydroxide).

Anhydrous copper sulfate (white) turns blue when it meets water.

Why does iodine turn blue when writing? Iodine is an alcohol solution of iodine, and pure iodine is a gray-black crystal. After the alcohol in iodine evaporates, iodine becomes dark, but it should become lighter soon, because iodine can be sublimated directly into gas without being converted into liquid and run away.

Among the seed components, starch is the one that turns blue when exposed to iodine. _ _ _ _ _ Dicotyledonous seeds are composed of seed coat and embryo, while monocotyledonous seeds are composed of seed coat, embryo and endosperm, and embryo is composed of embryo, hypocotyl, radicle and cotyledon. Generally, nutrients of monocotyledonous plants are stored in endosperm, while those of dicotyledonous plants are stored in cotyledons. There is starch in endosperm, and it is starch that turns blue when exposed to iodine.

So the answer is: √.

Why does iodine turn blue on paper? alkali

Why doesn't starch turn blue with lemonade and iodine? Lemonade can react with iodine, because without iodine, it won't turn blue when it comes to starch!

Citric acid has strong reducibility and can undergo redox reaction with iodine!