Adiabatic Expansion-system or surroundings?

[G1SG2]

Which one of the following best characterizes the process of air rising through the atmosphere?

A. Adiabatic, endergonic expansion
B. Adiabatic, exergonic expansion

I just wanted to clear up something. When a gas is compressed, heat is released and the process is exothermic. The gas gains energy and experiences an increase in temperature (E=W, since work is done on the gas, and since E is directly proportional to T, the gas experiences an increase in temperature). So, from the perspective of the system, there is an increase in temperature. However, the surrounding experiences a decrease in temperature since the surrounding does work on the gas. On the other hand, the expansion of a gas cools the gas. The gas experiences a decrease in temperature (since the gas does work, E=-W, and since E is negative, there is a decrease in temperature of the gas). However, the surroundings experience an increase in temperature since work is done on the surrounding. Then for the above question, is this process in terms of the surroundings? Or is my logic flawed? I thought we were supposed to always keep the system in mind?

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[matth87]

Which one of the following best characterizes the process of air rising through the atmosphere?

A. Adiabatic, endergonic expansion
B. Adiabatic, exergonic expansion

I just wanted to clear up something. When a gas is compressed, heat is released and the process is exothermic. The gas gains energy and experiences an increase in temperature (E=W, since work is done on the gas, and since E is directly proportional to T, the gas experiences an increase in temperature). So, from the perspective of the system, there is an increase in temperature. However, the surrounding experiences a decrease in temperature since the surrounding does work on the gas. On the other hand, the expansion of a gas cools the gas. The gas experiences a decrease in temperature (since the gas does work, E=-W, and since E is negative, there is a decrease in temperature of the gas). However, the surroundings experience an increase in temperature since work is done on the surrounding. Then for the above question, is this process in terms of the surroundings? Or is my logic flawed? I thought we were supposed to always keep the system in mind?

This line is not true:
When a gas is compressed, heat is released and the process is exothermic.
When a gas is compressed, it is being worked on by something outside the system. This is increasing the energy of the system. If the energy of the system increases, the temperature increase.
Everything else you said is correct.

Endothermic and Exothermic are terms that deal with the (delta)H of a reaction, we dont have a reaction here, just expansion of a gas.

Endorgonic and Exorgonic are terms that tell us about the (delta)G of a reaction, or its spontaneity. A -(delta)G is a spontaneous reaction and is exergonic. Since the gas is rapaidly expanding or becoming more disorganized "+(delta)S" we can say it is Exergonic.

This question really isn't in terms of the surrounds because there aren't any surrounding and it is not a closed system. It is really just talking about the spontaneity of the process.

What were answers C and D out of curiosity?

 

[G1SG2]

This line is not true:
When a gas is compressed, heat is released and the process is exothermic.
When a gas is compressed, it is being worked on by something outside the system. This is increasing the energy of the system. If the energy of the system increases, the temperature increase.
Everything else you said is correct.

Endothermic and Exothermic are terms that deal with the (delta)H of a reaction, we dont have a reaction here, just expansion of a gas.

Endorgonic and Exorgonic are terms that tell us about the (delta)G of a reaction, or its spontaneity. A -(delta)G is a spontaneous reaction and is exergonic. Since the gas is rapaidly expanding or becoming more disorganized "+(delta)S" we can say it is Exergonic.

This question really isn't in terms of the surrounds because there aren't any surrounding and it is not a closed system. It is really just talking about the spontaneity of the process.

What were answers C and D out of curiosity?

Gotchya. So, would it be safe to say that it's exothermic because the gas is losing energy by expanding (and specifically if its in a closed container, it is doing work on the surroundings and thus, is releasing heat to the surroundings making the process exothermic...since E=-W, and -E=decrease in temperature of the gas/increase in temperature of the surroundings, making it an exothermic process)? Hah, sorry if that sounded convoluted. C and D said it was an isothermal process, but the passage said it was adiabatic so I knew they were wrong.

 

[matth87]

Gotchya. So, would it be safe to say that it's exothermic because the gas is losing energy by expanding (and specifically if its in a closed container, it is doing work on the surroundings and thus, is releasing heat to the surroundings making the process exothermic...since E=-W, and -E=decrease in temperature of the gas/increase in temperature of the surroundings, making it an exothermic process)? Hah, sorry if that sounded convoluted. C and D said it was an isothermal process, but the passage said it was adiabatic so I knew they were wrong.

I tend to think of exothermic and endothermic more with reactions, when a gas expands its not really reacting. Exothermic and Endothermic are definitions which are used in conjunction with breaking and forming bonds of molecules. Here we have energy transfer in the form of work, not from breaking or forming bonds. You have everything correct with how the energy and temperature change, I think the definition of exothermic vs. exergonic is the only discrepancy here.

Exact definition for Enthalpy or (delta)H:
Enthaply is a measure of heat energy that is released or absorbed when bonds are broken and formed during a reaction that is run at constant pressure.

From that definition I would say it is "not safe" to use the words exothermic, but then again if the answer choice said exothermic instead of exergonic, I would have still pick it haha.