Chapter 20
The First Law of Thermodynamics
Thermodynamic Systems
A thermodynamic system is a set of objects whose thermodynamic properties are of interest. The system is considered to be embedded in its surroundings or ...
Work Done During Volume Change
In mechanics, work is done on an object when the force acting on it displaces the object. In thermodynamics, work done on a system can be estimated when ...
Path Between Thermodynamics States
Consider the two thermodynamic processes involving an ideal gas that are represented by paths AC and ABC in Figure 1:
In the first process for path A to ...
Heat and Free Expansion
The work done by a thermodynamic system depends not only on the initial and final states but also on the intermediate states—that is, on the path. ...
Internal Energy
The internal energy of a thermodynamic system is the sum of the kinetic and potential energies of all the molecules or entities in the system. The kinetic ...
First Law of Thermodynamics
A change in the internal energy of a system depends on the the net heat transfer into the system and the net work done by the system. The first law of ...
First Law Of Thermodynamics: Problem-Solving
The first law of thermodynamics states that the change in internal energy of the system is equal to the net heat transfer into the system minus the net ...
Cyclic Processes And Isolated Systems
A thermodynamic system with zero heat exchange and work is an isolated system. For these systems, the internal energy remains constant.
In the case of a ...
Isothermal Processes
A thermodynamic process that occurs at constant temperature is called an isothermal process. Heat slowly flows into the system or out of the system to ...
Isochoric and Isobaric Processes
A thermodynamic process that occurs at constant volume is called an isochoric process. According to the first law of thermodynamics, heat supplied or ...
Heat Capacities of an Ideal Gas I
Heat capacity is the ratio of heat absorbed by the substance corresponding to its temperature change. It is also called thermal capacity and the SI unit ...
Heat Capacities of an Ideal Gas II
For a system that undergoes a thermodynamic process at a constant volume condition, the heat absorbed is used only to increase the system's internal ...
Heat Capacities of an Ideal Gas III
The number of independent ways a gas molecule can move along straight line, rotate, and vibrate is called its degrees of freedom. Supposing d represents ...
Adiabatic Processes for an Ideal Gas
When an ideal gas is compressed adiabatically, that is, without adding heat, work is done on it, and its temperature increases. In an adiabatic expansion, ...
Pressure and Volume in an Adiabatic Process
Free expansion of a gas is an adiabatic process. However, there are few differences between free expansion and adiabatic expansion. During free expansion, ...
Work Done in an Adiabatic Process
Consider the adiabatic compression of an ideal gas in the cylinder of an automobile diesel engine. The gasoline vapor is injected into the cylinder of an ...
Thermodynamic Potentials
Thermodynamic potentials are state functions that are extremely useful in analyzing a thermodynamic system. They have dimensions of energy. The four ...
Maxwell's Thermodynamic Relations
Maxwell's thermodynamic relations are very useful in solving problems in thermodynamics. Each of Maxwell's relations relates a partial ...
Joule-Thomson Effect
The Joule-Thomson effect, also known as the Joule-Kelvin effect, describes the temperature change of a fluid when it is forced through a valve or porous ...
ABOUT JoVE
Copyright © 2025 MyJoVE Corporation. All rights reserved