2. Pour part of the solution in test tube 2 into test tube 3 for the next experiment.
3. Add a few drops of iodine solution into test tube 1 and test tube 2, and observe the phenomenon. It was found that the solution of test tube 1 was blue (starch turned blue when it met iodine), and there was no obvious phenomenon in test tube 2.
4. Drop 10% sodium hydroxide solution into the test tube 3, and adjust the pH value of the solution to about 9~ 10.
5. Add 3ml of sodium hydroxide solution into another test tube 4, and drop 4 drops of 2% copper sulfate solution, and blue copper hydroxide will precipitate immediately. Drop 65438 0 ml of hydrolysate into the test tube 3, shake it evenly, and heat it with an alcohol lamp until it boils. The color of the solution often changes from blue to yellow and then to green (yellow and blue mixed) and then to red. Finally, a red precipitate is formed. The reason is that copper hydroxide is reduced to produce red cuprous oxide, which is insoluble in water. Experimental conclusion: Starch can be hydrolyzed under the catalysis of acid. Hydrolysis process of starch: dextrin with small molecular weight (the product of incomplete hydrolysis of starch) is formed, and dextrin continues to hydrolyze to form maltose, and the final hydrolysis product is glucose.