Chemistry 9 Lesson 55: Practice: Properties of glucose
1. Theoretical Summary
1.1. Experiment purpose
a. Knowledge
Experimentally, verify and deepen knowledge of the chemical properties of glucose.
b. Skill
– Practice chemistry skills, solve practical chemistry exercises, experiment with small amounts of chemicals.
– Practice observing, describing, explaining phenomena and writing chemical equations of experiments.
1.2. Experimental skills
- Take liquid chemicals with a dropper, do not transfer the dropper of one chemical bottle to another.
- When heating the test tube, it is necessary to heat the surrounding area until it is hot, then focus on heating to avoid breaking the test tube.
- Each experiment needs to take the correct amount and type of chemicals.
- When instilling the solution into the test tube, it should be done slowly, so that the phenomenon is clearly observed.
- Recover chemicals, wash test tubes, clean the laboratory after the end of the practice session.
1.3. Theoretical basis
- Effect of glucose on silver nitrate in ammonia solution:
OLD6HtwelfthO6 + Ag2O \(\overset{NH_{3}}{\rightarrow}\) OLD6HtwelfthO7 (Gluconic Acid) + 2Ag\(\downarrow\)
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Distinguish between glucose, sucrose and starch:
Iodine adsorption into the empty slots in starch produces a blue-black color.
⇒ Method used to identify starch paste and vice versa (used to identify Iodine)
2. Conduct experiments
2.1. Experiment 1: Effect of glucose on silver nitrate in ammonia solution
a. Tools and chemicals
– Tools: Test tube, pipette, wooden clamp, alcohol lamp.
– Chemicals: solution of glucose, ammonia, silver nitrate.
b. Steps to take
– Add a few drops of silver nitrate solution to the ammonia solution in the test tube, shake gently.
– Then, add 1ml of glucose solution, shake gently, and gently heat it on the flame of an alcohol lamp (or put it in a cup of hot water).
– Observing the phenomenon.
c. Phenomena
There is a bright silvery substance that adheres to the walls of the test tube.
d. Explain
Due to Ag generated from the reaction on the wall of the test tube: C6HtwelfthO6 + Ag2O \(\overset{NH_{3}}{\rightarrow}\) OLD6HtwelfthO7 (Gluconic Acid) + 2Ag\(\downarrow\)
2.2. Experiment 2: Distinguishing glucose, sucrose, starch
a. Tools and chemicals
– Tools: Test tube, pipette, wooden clamp, alcohol lamp.
– Chemicals: Glucose solution, sucrose, starch paste, AgNO . solution3, ammonia.
b. Steps to take
There are 3 solutions of glucose, sucrose, and starch that are randomly numbered. Take each 1-2 ml solution into the corresponding numbered test tubes. Then conduct the following experiments:
– Step 1: Add 1-2 drops of iodine solution to 3 solutions in 3 test tubes. Observing the phenomenon.
– Step 2: Take 2 test tubes with numbers corresponding to the remaining 2 vials of solution, add 3ml of ammonia solution to each test tube, add 3 drops of AgNO solution3 in and shake vigorously. Continue to add 3ml of solution in the corresponding vial into the test tube and then immerse the test tube in a beaker of hot water. Observing the phenomenon.
c. Phenomenon, explanation
– Step 1: For 3 test samples containing solutions of glucose, sucrose, and starch, respectively, react with the iodine solution.
- Phenomenon: In any jar that appears blue, it is starch. On the other hand, glucose and sucrose do not react.
- Explanation: Iodine blues starch lake.
– Step 2: Continue for the test sample containing the remaining 2 solutions to react with the AgNO3 solution in NH3.
- Phenomenon: In any vial that appears silvery colored substance clinging to the wall of the test tube, it is a solution of glucose, the remaining substance is sucrose.
OLD6HtwelfthO6 + Ag2O → C6HtwelfthO7 + 2Ag
- Explanation: Glucose has a mirror reaction, Ag2O in SMALL3 Oxidizes glucose to gluconic acid and forms a silver precipitate on the wall of the test tube.
3. Conclusion
After the lesson to know:
- Ability to conduct experiments, observe reaction phenomena, explain and draw conclusions about the chemical properties of glucose.
- Confirm the correctness of the learned theory.
- Apply to explain related phenomena.
- Improve experimental skills, learn from experience for next time.
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