Навчальне дослідження 4. Виготовлення та дослідження пересичених розчинів — Transcript

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1. 0:00Hello to you, dear students. We
2. 0:05continue exploring solutions, and today
3. 0:07we will look at learning experiment
4. 0:10four. Preparation and study of
5. 0:12supersaturated solutions. Objective: to
6. 0:15learn how to prepare a saturated
7. 0:17solution at an elevated temperature and
8. 0:20obtain a supersaturated solution upon
9. 0:22cooling. To investigate the behavior of
10. 0:25a substance in a conditionally stable
11. 0:27state. Equipment and reagents. Sodium
12. 0:31thiosulfate, distilled water,
13. 0:33heat-resistant flask, water bath,
14. 0:35thermometer, stirring rod. Foil.
15. 0:39Procedure. Pour 28 g of sodium
16. 1:00thiosulfate into a beaker and add 20 ml
17. 1:04of water. Place the beaker into a water
18. 1:43bath. Heat the mixture to a temperature
19. 1:48of about 50-60 ° C, stirring it
20. 1:51periodically. Observe the complete
21. 2:19dissolution of the crystals and the
22. 2:21mixture turning into a nearly
23. 2:23transparent liquid. Cover the beaker
24. 2:28with foil to protect it from foreign
25. 2:30particles in the air. Leave the
26. 2:34solution to cool slowly to room
27. 2:36temperature, without shaking or jarring
28. 2:39it. With slow and calm cooling, we
29. 2:43obtain a supersaturated solution, a
30. 2:46conditionally stable system that
31. 2:48contains more dissolved solute than is
32. 2:51possible at room temperature. After
33. 2:55complete cooling, remove the protective
34. 2:58foil and dip the stirring rod into the
35. 3:01clear solution. This creates a
36. 3:04crystallization center, which leads to
37. 3:06the precipitation of a solid phase.
38. 3:09Observe the appearance of crystals
39. 3:11throughout the beaker. The
40. 3:13crystallization process is accompanied
41. 3:16by the release of a small amount of
42. 3:18heat. Therefore, it is an exothermic
43. 3:20process. Because the system
44. 3:22transitioned from an energetically
45. 3:24unstable state to a stable crystalline
46. 3:26state. Describe and explain the
47. 3:32demonstrated process. Write your
48. 3:46conclusions for the work. Answer the
49. 3:48questions. Why is a sodium thiosulfate
50. 3:51solution called relatively stable?
51. 3:55Where in everyday life can we encounter
52. 3:57the use of such a principle of instant
53. 3:59crystallization with heat release?
54. 4:03Reflection. What surprised you the most
55. 4:06? Which stage of the work is the most
56. 4:08crucial? If this video was clear and
57. 4:12informative, please leave a like, write
58. 4:14a comment, and subscribe if you haven't
59. 4:16already. Thank you for watching, and I
60. 4:20wish you success in your study of
61. 4:22chemistry.