The principle of starch turning blue with iodine is as follows:
The principle of iodine turning blue with starch is due to the iodine molecules entering into the starch helix circle, forming starch iodine complex. When the chain length is less than 6 glucosyl, it will not be colored, when the average length of the chain is 20 glucosyl, it will be red, and when it is greater than 60 glucosyl, it will be blue.
The principle that iodine turns blue when it meets starch is that the essence of the reaction between starch and iodine is the generation of an inclusion complex, which makes the color blue. Starch is a plant polysaccharide that is formed by the dehydration and condensation of hundreds to thousands of glucose monomers. It usually consists of two parts, straight-chain starch and branched-chain starch.
The reason starch reacts with iodine in a color-presenting way is because iodine molecules enter the spiral rings of starch and form a starch-iodine complex. As for what color is presented is related to the length of the starch sugar chain. When the chain length is less than 6 glucose groups, it will not show color, and when the average length of the chain is 20 glucose groups, it will show red color.
Precautions for doing chemistry labs:
1. Wear proper lab clothing
Wear lab coats for the lab, long-sleeved clothing and long pants can provide better protection. Also, wear lab safety glasses, gloves and lab shoes to prevent chemical spills. Learn about lab safety facilities, including eye wash, safety shower, and fire extinguisher, to ensure that you can respond quickly to emergencies.
2. Strictly follow the experimental operating procedures
Before conducting experiments, read the experimental operating procedures carefully and follow them. Do not change the experimental steps or parameters arbitrarily. Pay attention to laboratory ventilation, the laboratory to maintain good ventilation, to ensure that there is enough fresh air flow, to exclude harmful gases.
3, pay attention to safety when using chemicals
Correct use of chemicals, follow the laboratory storage and handling requirements. Pay attention to the nature, toxicity and danger of chemicals, avoid direct contact with skin and inhalation of harmful gases. Handle sharp and high-temperature equipment with care. Be careful when using sharp instruments such as knives and scissors to avoid scratches or cuts. For high-temperature equipment, such as burners and heaters, operate with care to avoid burns.
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