Entropy is defined as heat flow / temperature at equilibrium: dS = dQ/T. If the process is adiabatic and reversible, this means there is no heat flow and at all times the system is in equilibrium. So dQ=0. So that pretty much means that dS = 0 (ie. no change in entropy).grscott_2000 said:If a process is adiabatic and reversible, such as a gas in a tube that has been compressed, is it true to say that there is no change in entropy from the gas being uncompressed to being compressed?
If not, why not?
Entropy is a measure of the disorder or randomness of a system. It is a thermodynamic property that describes the amount of energy that is unavailable for work in a system.
In an adiabatic process, there is no exchange of heat between the system and its surroundings. This means that any change in entropy is solely due to the work done on or by the system. As a result, adiabatic processes are often characterized by a change in entropy.
The change in entropy of a system is directly proportional to the change in temperature. This means that as the temperature increases, the entropy of the system also increases. Conversely, as the temperature decreases, the entropy decreases as well.
The change in entropy can have a significant impact on the efficiency of a process. In general, an increase in entropy leads to a decrease in efficiency, as more energy is lost in the form of heat. This is why it is important to minimize entropy in order to maximize the efficiency of a process.
According to the second law of thermodynamics, the total entropy of a closed system will always increase over time. While it is possible to reduce the entropy of a specific system, the overall entropy of the universe will always continue to increase. This is known as the arrow of time and is a fundamental principle in thermodynamics.