Does Isothermal Heat Flow Out Contradict the Second Law of Thermodynamics?

In summary, during a reversible isothermal process where heat flows out of the system, the entropy of the system decreases but the entropy of the surroundings increases by an equal amount. This does not violate the second law of thermodynamics, as the total change in entropy for the entire system is positive. The word "system" can be interpreted differently in this context, but in terms of the second law, it refers to everything that loses or gains heat during the process. Therefore, the decrease in entropy for the system is balanced by an increase in entropy for the surroundings.
  • #1
neelakash
511
1

Homework Statement



When there is a heat flow out of the system during a reversible isothermal processthe entropy of the system decreases.Why does this not violate the 2nd law of thermodynamics?

Homework Equations


The Attempt at a Solution

I hope this is correct.Please check and confirm.


Because the question uses the word "system" quite loosely. They are using "system" to mean the gas or other working substance from which the heat flows. But in terms of the second law, the word "system" refers to everything that loses or gains heat during the process.

So while the gas releases heat and the entropy of the gas decreases, the heat is absorbed by the environment (which must be included in the "system") and the entropy of the environment increases. Overall the total change in entropy is positive, as the increase for the environment is greater than the decrease for the gas.
 
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  • #2
when there is a decrease in this enrophy, the entropy of the surroundings increases, u are quite right. system in the law refers to everything
 
  • #3
OK thank you.
 
  • #4
In fact, if it's reversable, then the entropy increase of the surroundings exactly matches the entropy decrease of the system.
 

FAQ: Does Isothermal Heat Flow Out Contradict the Second Law of Thermodynamics?

What is thermodynamics and why is it important?

Thermodynamics is the study of the relationships between heat, energy, and work. It is important because it helps us understand how energy is transferred and transformed within a system, and how these processes affect the behavior of matter.

What is the first law of thermodynamics?

The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or transformed from one form to another.

How is the second law of thermodynamics applied in thermodynamic problems?

The second law of thermodynamics states that the total entropy of a closed system will always increase over time. In thermodynamic problems, this law is used to determine the direction of energy flow and predict the efficiency of energy conversions.

What are some common examples of thermodynamic problems?

Some common examples of thermodynamic problems include calculating the efficiency of heat engines, determining the change in temperature of a gas under various conditions, and predicting the amount of work that can be done by a system.

How can thermodynamics be applied in real-world situations?

Thermodynamics has many practical applications, such as in the design of engines and power plants, refrigeration and air conditioning systems, and chemical processes. It also plays a crucial role in understanding and addressing global issues such as climate change and energy sustainability.

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