Thermodynamics:
? Describes macroscopic properties of equilibrium systems
? Entirely Empirical
? Built on 4 Laws and “simple” mathematics:
th0 Law ? Defines Temperature (T)
st1 Law ? Defines Energy (U)
nd2 Law ? Defines Entropy (S)
rd3 Law ? Gives Numerical Value to Entropy
These laws are UNIVERSALLY VALID, they cannot be circumvented.
Definitions:
• System: The part of the Universe that we choose to study
• Surroundings: The rest of the Universe
• Boundary: The surface dividing the System from the Surroundings
Systems can be:
• Open: Mass and Energy can transfer between the System and the Surroundings
• Closed: Energy can transfer between the System and the Surroundings, but NOT mass
• Isolated: Neither Mass nor Energy can transfer between the System and the Surroundings
Describing systems requires:
• A few macroscopic properties: p, T, V, n, m, …
• Knowledge if System is Homogeneous or Heterogeneous
• Knowledge if System is in Equilibrium State
• Knowledge of the number of components
Two classes of Properties:
• Extensive: Depend on the size of the system (n, m, V,…)
• Intensive: Independent of the size of the system V (T, p, V = ,…) n
The State of a System at Equilibrium:
• Defined by the collection of all macroscopic properties that are described by State variables (p, n, T, V,…)
[INDEPENDENT of the HISTORY of the SYSTEM]
• For a one-component System, all that is required is “n” and 2 variables. All other properties then follow.
V = f (n, p, T) or p = g(n, V, T)
• Process: Describes the Path
- Reversible (always in Equilibrium)
- Irreversible (defines direction of time)
- Adiabatic (no heat transfer between system and surroundings)
- Isobaric (constant pressure)
- Isothermal (constant temperature)
- Constant Volume
When a hot object is placed in thermal contact with a cold object,
heat flows from the warmer to the cooler object. This continues
until they are in thermal equilibrium (the heat flow stops). At this
point, both bodies are said to have the same “temperature”.
thThis intuitively straightforward idea is formalized in the 0 Law of
thermodynamics and is made practical through the development of
thermometers and temperature scales.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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