The Zeroth Law of Thermodynamics: Thermal Equilibrium — Transcript

Full transcript

1. 0:00Professor Dave here, let's discuss the
2. 0:02zeroth law of thermodynamics.
3. 0:11Thermodynamics is a tricky subject that
4. 0:13must be studied in chemistry, physics,
5. 0:15engineering, and many other courses of
6. 0:18academic study, because it has an
7. 0:20incredible impact on the behavior of
8. 0:22matter and energy. At first, thermodynamic
9. 0:26concepts may seem impossible to
10. 0:28understand, but if you go over the basics
11. 0:31enough times they start to make sense
12. 0:33and you can continue to learn more about
13. 0:36the subject as needed for your field of
14. 0:39study or level of desired knowledge.
15. 0:42We will begin our analysis with the
16. 0:44infamous laws of thermodynamics. Just
17. 0:48like Newton's laws of motion there is a
18. 0:50first, second, and third law, but later in
19. 0:53the development of the field a more
20. 0:54fundamental law was added and dubbed the
21. 0:57zeroth law, so let's start there.
22. 1:01The zeroth law of thermodynamics deals with
23. 1:03thermal equilibrium, which as we recall
24. 1:06describes a situation in which there is
25. 1:09no net heat flow between two systems.
26. 1:12The zeroth law states that if two systems
27. 1:14are in thermal equilibrium with a third
28. 1:17system, then those two systems are also
29. 1:19in thermal equilibrium with each other.
30. 1:22In other words, if A is in thermal
31. 1:24equilibrium with B which is in thermal
32. 1:27equilibrium with C, A and C are also in
33. 1:31equilibrium. This may seem like a trivial
34. 1:33statement but it is an important one
35. 1:36because it means that two objects at the
36. 1:39same temperature will not exhibit heat
37. 1:41flow when they come into contact with
38. 1:43one another. This marks temperature as
39. 1:47the indicator of thermal equilibrium.
40. 1:50If two objects are in thermal equilibrium
41. 1:52with thermometers that read the same
42. 1:56temperature, the objects will be in
43. 1:58thermal equilibrium with each other
44. 2:01which therefore allows us to gather all
45. 2:03kinds of thermodynamic data in our
46. 2:06laboratories. In studying thermodynamics
47. 2:09we must also learn certain definitions.
48. 2:13We will want to be able to define a
49. 2:14system as the collection of objects we
50. 2:17are examining while the surroundings
51. 2:19represent the environment surrounding
52. 2:22the system, which is technically the rest
53. 2:25of the universe. Some systems allow heat
54. 2:28to flow in and out. These systems have
55. 2:31diathermal walls. Some systems do not
56. 2:35allow heat to flow in and out. These
57. 2:37systems have adiabatic walls. No system
58. 2:41can be truly adiabatic, but it is a
59. 2:43useful approximation when we do
60. 2:46calculations involving systems that
61. 2:48permit only negligible heat transfer.
62. 2:51With these definitions out of the way, we
63. 2:54can move on to the first law of thermodynamics.
64. 2:58Thanks for watching, guys. Subscribe to my channel for
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