1. Add 0.5g starch and 4ml water to test tube 1, and add 0.5g starch and 4ml 20 sulfuric acid solution to test tube 2. Heat the test tubes respectively for 3~4 minutes.

2. Pour part of the solution in test tube 2 into test tube 3 and reserve it for the next experiment.

3. Add a few drops of iodine solution to test tube 1 and test tube 2 and observe the phenomenon. It was found that the solution in test tube 1 was blue (starch turned blue when exposed to iodine), but there was no obvious phenomenon in test tube 2. The reason for the different phenomena is that starch undergoes hydrolysis reaction under acidic conditions and heating conditions.

4. Drop 10% alkali solution into test tube 3 to neutralize the sulfuric acid in the solution and make the solution weakly alkaline, so that the pH value of the solution is about 9~10.

5. Take another test tube 4, add 3 ml of sodium hydroxide solution, and drop 4 drops of 2 copper sulfate solution into it, and a blue copper hydroxide precipitate will immediately form. Then take 1 ml of the hydrolyzate in test tube 3 and drop it in. After shaking and mixing evenly, use an alcohol lamp to heat and boil. The color of the solution often changes from blue to yellow to green (a mixture of yellow and blue) to red. Eventually a red precipitate forms. The reason is that copper hydroxide is reduced to produce red cuprous oxide that is insoluble in water.

Experimental conclusion: Starch can be hydrolyzed under the catalysis of acid; the hydrolysis process of starch: dextrin with a smaller molecular weight (the product of incomplete hydrolysis of starch) is first formed, and the dextrin continues to be hydrolyzed to form maltose , the final hydrolysis product is glucose.