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If the first law of thermodynamics ensures conservation of energy, why does it allow systems to lose energy?
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$begingroup$
I am learning the basics of Thermodynamics.
Everywhere I read about the first law, it states "conservation of energy", and talks about how change in internal energy equals heat and work transfer.
I am aware of work transfer being considered positive and negative depending on the point of view we want to set.
That is okay.
But it confuses me to see the word "conservation".
If we take a very simple or at least very common real process like putting a plastic bottle completely filled with liquid water into a freezer (or whatever environment that is constantly under 273 K) and wait for thermal equilibrium to happen, the bottle will have expanded because water will have frozen increasing its volume and pushing the bottle's limits.
In this case:
The system (the bottle) has lost or given away a whatever amount of heat and it will also have generated a work transfer (to make the bottle expand).
It doesn't matter if we consider that work positive once or negative twice, in both cases energy has left the system in the form of work.
The total amount of internal energy of the system has clearly decreased.
So apparently there isn't really any "conservation" happening.
I do not intend to hate on thermodynamics, it's actually beautiful, I just want to understand the semantics.
I read other similar questions like this one, but in none did I find a clear answer.
thermodynamics energy-conservation
edited 32 mins ago
knzhou
54.6k14 gold badges155 silver badges262 bronze badges
asked yesterday
Alvaro FranzAlvaro Franz
598 bronze badges
$endgroup$
add a comment |
$begingroup$
I am learning the basics of Thermodynamics.
Everywhere I read about the first law, it states "conservation of energy", and talks about how change in internal energy equals heat and work transfer.
I am aware of work transfer being considered positive and negative depending on the point of view we want to set.
That is okay.
But it confuses me to see the word "conservation".
If we take a very simple or at least very common real process like putting a plastic bottle completely filled with liquid water into a freezer (or whatever environment that is constantly under 273 K) and wait for thermal equilibrium to happen, the bottle will have expanded because water will have frozen increasing its volume and pushing the bottle's limits.
In this case:
The system (the bottle) has lost or given away a whatever amount of heat and it will also have generated a work transfer (to make the bottle expand).
It doesn't matter if we consider that work positive once or negative twice, in both cases energy has left the system in the form of work.
The total amount of internal energy of the system has clearly decreased.
So apparently there isn't really any "conservation" happening.
I do not intend to hate on thermodynamics, it's actually beautiful, I just want to understand the semantics.
I read other similar questions like this one, but in none did I find a clear answer.
thermodynamics energy-conservation
edited 32 mins ago
knzhou
54.6k14 gold badges155 silver badges262 bronze badges
asked yesterday
Alvaro FranzAlvaro Franz
598 bronze badges
$endgroup$
10
$begingroup$
It's conservation of total energy, not just the system's energy.
$endgroup$
– knzhou
yesterday
2
$begingroup$
In your example, the system would have to be the bottle AND the freezer, and the conservation of energy would imply that whatever heat was lost by the bottle must have been absorbed by the freezer. In general you want to consider closed systems, i.e. systems which do not interact with the environment (as the bottle taken alone is doing with the freezer).
$endgroup$
– Jxx
yesterday
1
$begingroup$
"conservation of energy", and talks about how internal energy equals heat and work transfer. This is wrong. It should be change in internal energy.
$endgroup$
– Aaron Stevens
23 hours ago
5
$begingroup$
This is an input - output = accumulation kind of thing. It's like a bank account, for which "conservation of money" exists. Deposits - Payments (checks) = change in bank balance. If money was disappearing, the FEDs would have to come in and arrest someone. In the first law, the change in internal energy is analogous to the change in bank balance. Heat added minus work done is analogous to deposits minus payments (although unlike a bank account, heat added and work done can both be positive or negative).
$endgroup$
– Chet Miller
23 hours ago
$begingroup$
Reminder: Answers go in the answers, not in comments. This is not directed at any one comment.
$endgroup$
– David Conrad
6 hours ago
add a comment |
$begingroup$
I am learning the basics of Thermodynamics.
Everywhere I read about the first law, it states "conservation of energy", and talks about how change in internal energy equals heat and work transfer.
I am aware of work transfer being considered positive and negative depending on the point of view we want to set.
That is okay.
But it confuses me to see the word "conservation".
If we take a very simple or at least very common real process like putting a plastic bottle completely filled with liquid water into a freezer (or whatever environment that is constantly under 273 K) and wait for thermal equilibrium to happen, the bottle will have expanded because water will have frozen increasing its volume and pushing the bottle's limits.
In this case:
The system (the bottle) has lost or given away a whatever amount of heat and it will also have generated a work transfer (to make the bottle expand).
It doesn't matter if we consider that work positive once or negative twice, in both cases energy has left the system in the form of work.
The total amount of internal energy of the system has clearly decreased.
So apparently there isn't really any "conservation" happening.
I do not intend to hate on thermodynamics, it's actually beautiful, I just want to understand the semantics.
I read other similar questions like this one, but in none did I find a clear answer.
thermodynamics energy-conservation
edited 32 mins ago
knzhou
54.6k14 gold badges155 silver badges262 bronze badges
asked yesterday
Alvaro FranzAlvaro Franz
598 bronze badges
$endgroup$
I am learning the basics of Thermodynamics.
Everywhere I read about the first law, it states "conservation of energy", and talks about how change in internal energy equals heat and work transfer.
I am aware of work transfer being considered positive and negative depending on the point of view we want to set.
That is okay.
But it confuses me to see the word "conservation".
If we take a very simple or at least very common real process like putting a plastic bottle completely filled with liquid water into a freezer (or whatever environment that is constantly under 273 K) and wait for thermal equilibrium to happen, the bottle will have expanded because water will have frozen increasing its volume and pushing the bottle's limits.
In this case:
The system (the bottle) has lost or given away a whatever amount of heat and it will also have generated a work transfer (to make the bottle expand).
It doesn't matter if we consider that work positive once or negative twice, in both cases energy has left the system in the form of work.
The total amount of internal energy of the system has clearly decreased.
So apparently there isn't really any "conservation" happening.
I do not intend to hate on thermodynamics, it's actually beautiful, I just want to understand the semantics.
I read other similar questions like this one, but in none did I find a clear answer.
thermodynamics energy-conservation
thermodynamics energy-conservation
edited 32 mins ago
knzhou
54.6k14 gold badges155 silver badges262 bronze badges
asked yesterday
Alvaro FranzAlvaro Franz
598 bronze badges
edited 32 mins ago
knzhou
54.6k14 gold badges155 silver badges262 bronze badges
asked yesterday
Alvaro FranzAlvaro Franz
598 bronze badges
edited 32 mins ago
knzhou
54.6k14 gold badges155 silver badges262 bronze badges
edited 32 mins ago
knzhou
54.6k14 gold badges155 silver badges262 bronze badges
edited 32 mins ago
knzhou
54.6k14 gold badges155 silver badges262 bronze badges
54.6k14 gold badges155 silver badges262 bronze badges
asked yesterday
Alvaro FranzAlvaro Franz
598 bronze badges
asked yesterday
Alvaro FranzAlvaro Franz
598 bronze badges
asked yesterday
Alvaro FranzAlvaro Franz
598 bronze badges
598 bronze badges
10
$begingroup$
It's conservation of total energy, not just the system's energy.
$endgroup$
– knzhou
yesterday
2
$begingroup$
In your example, the system would have to be the bottle AND the freezer, and the conservation of energy would imply that whatever heat was lost by the bottle must have been absorbed by the freezer. In general you want to consider closed systems, i.e. systems which do not interact with the environment (as the bottle taken alone is doing with the freezer).
$endgroup$
– Jxx
yesterday
1
$begingroup$
"conservation of energy", and talks about how internal energy equals heat and work transfer. This is wrong. It should be change in internal energy.
$endgroup$
– Aaron Stevens
23 hours ago
5
$begingroup$
This is an input - output = accumulation kind of thing. It's like a bank account, for which "conservation of money" exists. Deposits - Payments (checks) = change in bank balance. If money was disappearing, the FEDs would have to come in and arrest someone. In the first law, the change in internal energy is analogous to the change in bank balance. Heat added minus work done is analogous to deposits minus payments (although unlike a bank account, heat added and work done can both be positive or negative).
$endgroup$
– Chet Miller
23 hours ago
$begingroup$
Reminder: Answers go in the answers, not in comments. This is not directed at any one comment.
$endgroup$
– David Conrad
6 hours ago
add a comment |
10
$begingroup$
It's conservation of total energy, not just the system's energy.
$endgroup$
– knzhou
yesterday
2
$begingroup$
In your example, the system would have to be the bottle AND the freezer, and the conservation of energy would imply that whatever heat was lost by the bottle must have been absorbed by the freezer. In general you want to consider closed systems, i.e. systems which do not interact with the environment (as the bottle taken alone is doing with the freezer).
$endgroup$
– Jxx
yesterday
1
$begingroup$
"conservation of energy", and talks about how internal energy equals heat and work transfer. This is wrong. It should be change in internal energy.
$endgroup$
– Aaron Stevens
23 hours ago
5
$begingroup$
This is an input - output = accumulation kind of thing. It's like a bank account, for which "conservation of money" exists. Deposits - Payments (checks) = change in bank balance. If money was disappearing, the FEDs would have to come in and arrest someone. In the first law, the change in internal energy is analogous to the change in bank balance. Heat added minus work done is analogous to deposits minus payments (although unlike a bank account, heat added and work done can both be positive or negative).
$endgroup$
– Chet Miller
23 hours ago
$begingroup$
Reminder: Answers go in the answers, not in comments. This is not directed at any one comment.
$endgroup$
– David Conrad
6 hours ago
10
10
$begingroup$
It's conservation of total energy, not just the system's energy.
$endgroup$
– knzhou
yesterday
$begingroup$
It's conservation of total energy, not just the system's energy.
$endgroup$
– knzhou
yesterday
2
2
$begingroup$
In your example, the system would have to be the bottle AND the freezer, and the conservation of energy would imply that whatever heat was lost by the bottle must have been absorbed by the freezer. In general you want to consider closed systems, i.e. systems which do not interact with the environment (as the bottle taken alone is doing with the freezer).
$endgroup$
– Jxx
yesterday
$begingroup$
In your example, the system would have to be the bottle AND the freezer, and the conservation of energy would imply that whatever heat was lost by the bottle must have been absorbed by the freezer. In general you want to consider closed systems, i.e. systems which do not interact with the environment (as the bottle taken alone is doing with the freezer).
$endgroup$
– Jxx
yesterday
1
1
$begingroup$
"conservation of energy", and talks about how internal energy equals heat and work transfer. This is wrong. It should be change in internal energy.
$endgroup$
– Aaron Stevens
23 hours ago
$begingroup$
"conservation of energy", and talks about how internal energy equals heat and work transfer. This is wrong. It should be change in internal energy.
$endgroup$
– Aaron Stevens
23 hours ago
5
5
$begingroup$
This is an input - output = accumulation kind of thing. It's like a bank account, for which "conservation of money" exists. Deposits - Payments (checks) = change in bank balance. If money was disappearing, the FEDs would have to come in and arrest someone. In the first law, the change in internal energy is analogous to the change in bank balance. Heat added minus work done is analogous to deposits minus payments (although unlike a bank account, heat added and work done can both be positive or negative).
$endgroup$
– Chet Miller
23 hours ago
$begingroup$
This is an input - output = accumulation kind of thing. It's like a bank account, for which "conservation of money" exists. Deposits - Payments (checks) = change in bank balance. If money was disappearing, the FEDs would have to come in and arrest someone. In the first law, the change in internal energy is analogous to the change in bank balance. Heat added minus work done is analogous to deposits minus payments (although unlike a bank account, heat added and work done can both be positive or negative).
$endgroup$
– Chet Miller
23 hours ago
$begingroup$
Reminder: Answers go in the answers, not in comments. This is not directed at any one comment.
$endgroup$
– David Conrad
6 hours ago
$begingroup$
Reminder: Answers go in the answers, not in comments. This is not directed at any one comment.
$endgroup$
– David Conrad
6 hours ago
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
“Conserved” doesn’t mean “never changes”. It means “this stuff is real, and the only way you have less or more is if some is taken away or added”. You can then follow that additions or subtractions.
Since your cold bottle has less energy, the conservation law says that energy has not disappeared, it’s just gone somewhere. You can find it. You can figure out how it got there.
answered 17 hours ago
Bob JacobsenBob Jacobsen
7,62211 silver badges24 bronze badges
$endgroup$
add a comment |
$begingroup$
I'm not sure why people are saying this only applies to closed systems. This law actually applies to all systems. The first law is conservation of energy. It says the change in energy is equal to the energy that enters/leaves it in the form of work or heat. i.e.
$$Delta U=W+Q$$
where $U$ is the internal energy, $W$ is the work done on the system, and $Q$ is the heat that enters the system. This equation essentially just says we can track where the energy of our system is coming from/going to. It isn't suddenly appearing from or disappearing to some "unknown nowhere". It's energy conservation.
In your system, heat left the system, and the system did some work on the environment I suppose (though this might be negligible). In any case, $Q<0$ and $W<0$, so it should be no surprise that $Delta U<0$. Energy has left your system (and has gone somewhere else), so the internal energy has decreased. Energy conservation is true, and it's present in the first law here.
answered 23 hours ago
Aaron StevensAaron Stevens
21.3k4 gold badges37 silver badges76 bronze badges
$endgroup$
6
$begingroup$
In engineering, a closed system is one in which no mass enters of leaves, but one which can exchange of heat and work with the surroundings. What you are envisioning as a closed system is what we call an "isolated system."
$endgroup$
– Chet Miller
22 hours ago
$begingroup$
@ChetMiller Ah ok, thanks. I have removed my parenthetical comment. In any case, the first law still applies to all systems.
$endgroup$
– Aaron Stevens
22 hours ago
$begingroup$
I accepted Bob Jacobsen's answer because it goes straight to the semantics and makes it clear at one shot. Chet Miller's comment under the original question also did. I still appreciate your answer and it also helps. The combination of both should be the final one. All the best and thanks again.
$endgroup$
– Alvaro Franz
15 hours ago
2
$begingroup$
@AlvaroFranz Glad I could help
$endgroup$
– Aaron Stevens
12 hours ago
add a comment |
$begingroup$
Conserved here doesn't mean that it is conserved only for your system (Not unless it's an isolated system). It is conserved for the whole universe. The total energy is constant. In performing any work or task , all you are doing is taking some energy from the surrounding and giving it to the system or vice versa. These 2 effects balance out or cancel each other if you consider the whole universe making thermodynamics "Perfectly balanced, as all things should be"
answered 3 hours ago
RandomAspirantRandomAspirant
1193 bronze badges
New contributor
RandomAspirant is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
“Conserved” doesn’t mean “never changes”. It means “this stuff is real, and the only way you have less or more is if some is taken away or added”. You can then follow that additions or subtractions.
Since your cold bottle has less energy, the conservation law says that energy has not disappeared, it’s just gone somewhere. You can find it. You can figure out how it got there.
answered 17 hours ago
Bob JacobsenBob Jacobsen
7,62211 silver badges24 bronze badges
$endgroup$
add a comment |
$begingroup$
“Conserved” doesn’t mean “never changes”. It means “this stuff is real, and the only way you have less or more is if some is taken away or added”. You can then follow that additions or subtractions.
Since your cold bottle has less energy, the conservation law says that energy has not disappeared, it’s just gone somewhere. You can find it. You can figure out how it got there.
answered 17 hours ago
Bob JacobsenBob Jacobsen
7,62211 silver badges24 bronze badges
$endgroup$
add a comment |
$begingroup$
“Conserved” doesn’t mean “never changes”. It means “this stuff is real, and the only way you have less or more is if some is taken away or added”. You can then follow that additions or subtractions.
Since your cold bottle has less energy, the conservation law says that energy has not disappeared, it’s just gone somewhere. You can find it. You can figure out how it got there.
answered 17 hours ago
Bob JacobsenBob Jacobsen
7,62211 silver badges24 bronze badges
$endgroup$
“Conserved” doesn’t mean “never changes”. It means “this stuff is real, and the only way you have less or more is if some is taken away or added”. You can then follow that additions or subtractions.
Since your cold bottle has less energy, the conservation law says that energy has not disappeared, it’s just gone somewhere. You can find it. You can figure out how it got there.
answered 17 hours ago
Bob JacobsenBob Jacobsen
7,62211 silver badges24 bronze badges
answered 17 hours ago
Bob JacobsenBob Jacobsen
7,62211 silver badges24 bronze badges
answered 17 hours ago
Bob JacobsenBob Jacobsen
7,62211 silver badges24 bronze badges
answered 17 hours ago
Bob JacobsenBob Jacobsen
7,62211 silver badges24 bronze badges
7,62211 silver badges24 bronze badges
add a comment |
add a comment |
$begingroup$
I'm not sure why people are saying this only applies to closed systems. This law actually applies to all systems. The first law is conservation of energy. It says the change in energy is equal to the energy that enters/leaves it in the form of work or heat. i.e.
$$Delta U=W+Q$$
where $U$ is the internal energy, $W$ is the work done on the system, and $Q$ is the heat that enters the system. This equation essentially just says we can track where the energy of our system is coming from/going to. It isn't suddenly appearing from or disappearing to some "unknown nowhere". It's energy conservation.
In your system, heat left the system, and the system did some work on the environment I suppose (though this might be negligible). In any case, $Q<0$ and $W<0$, so it should be no surprise that $Delta U<0$. Energy has left your system (and has gone somewhere else), so the internal energy has decreased. Energy conservation is true, and it's present in the first law here.
answered 23 hours ago
Aaron StevensAaron Stevens
21.3k4 gold badges37 silver badges76 bronze badges
$endgroup$
6
$begingroup$
In engineering, a closed system is one in which no mass enters of leaves, but one which can exchange of heat and work with the surroundings. What you are envisioning as a closed system is what we call an "isolated system."
$endgroup$
– Chet Miller
22 hours ago
$begingroup$
@ChetMiller Ah ok, thanks. I have removed my parenthetical comment. In any case, the first law still applies to all systems.
$endgroup$
– Aaron Stevens
22 hours ago
$begingroup$
I accepted Bob Jacobsen's answer because it goes straight to the semantics and makes it clear at one shot. Chet Miller's comment under the original question also did. I still appreciate your answer and it also helps. The combination of both should be the final one. All the best and thanks again.
$endgroup$
– Alvaro Franz
15 hours ago
2
$begingroup$
@AlvaroFranz Glad I could help
$endgroup$
– Aaron Stevens
12 hours ago
add a comment |
$begingroup$
I'm not sure why people are saying this only applies to closed systems. This law actually applies to all systems. The first law is conservation of energy. It says the change in energy is equal to the energy that enters/leaves it in the form of work or heat. i.e.
$$Delta U=W+Q$$
where $U$ is the internal energy, $W$ is the work done on the system, and $Q$ is the heat that enters the system. This equation essentially just says we can track where the energy of our system is coming from/going to. It isn't suddenly appearing from or disappearing to some "unknown nowhere". It's energy conservation.
In your system, heat left the system, and the system did some work on the environment I suppose (though this might be negligible). In any case, $Q<0$ and $W<0$, so it should be no surprise that $Delta U<0$. Energy has left your system (and has gone somewhere else), so the internal energy has decreased. Energy conservation is true, and it's present in the first law here.
answered 23 hours ago
Aaron StevensAaron Stevens
21.3k4 gold badges37 silver badges76 bronze badges
$endgroup$
6
$begingroup$
In engineering, a closed system is one in which no mass enters of leaves, but one which can exchange of heat and work with the surroundings. What you are envisioning as a closed system is what we call an "isolated system."
$endgroup$
– Chet Miller
22 hours ago
$begingroup$
@ChetMiller Ah ok, thanks. I have removed my parenthetical comment. In any case, the first law still applies to all systems.
$endgroup$
– Aaron Stevens
22 hours ago
$begingroup$
I accepted Bob Jacobsen's answer because it goes straight to the semantics and makes it clear at one shot. Chet Miller's comment under the original question also did. I still appreciate your answer and it also helps. The combination of both should be the final one. All the best and thanks again.
$endgroup$
– Alvaro Franz
15 hours ago
2
$begingroup$
@AlvaroFranz Glad I could help
$endgroup$
– Aaron Stevens
12 hours ago
add a comment |
$begingroup$
I'm not sure why people are saying this only applies to closed systems. This law actually applies to all systems. The first law is conservation of energy. It says the change in energy is equal to the energy that enters/leaves it in the form of work or heat. i.e.
$$Delta U=W+Q$$
where $U$ is the internal energy, $W$ is the work done on the system, and $Q$ is the heat that enters the system. This equation essentially just says we can track where the energy of our system is coming from/going to. It isn't suddenly appearing from or disappearing to some "unknown nowhere". It's energy conservation.
In your system, heat left the system, and the system did some work on the environment I suppose (though this might be negligible). In any case, $Q<0$ and $W<0$, so it should be no surprise that $Delta U<0$. Energy has left your system (and has gone somewhere else), so the internal energy has decreased. Energy conservation is true, and it's present in the first law here.
answered 23 hours ago
Aaron StevensAaron Stevens
21.3k4 gold badges37 silver badges76 bronze badges
$endgroup$
I'm not sure why people are saying this only applies to closed systems. This law actually applies to all systems. The first law is conservation of energy. It says the change in energy is equal to the energy that enters/leaves it in the form of work or heat. i.e.
$$Delta U=W+Q$$
where $U$ is the internal energy, $W$ is the work done on the system, and $Q$ is the heat that enters the system. This equation essentially just says we can track where the energy of our system is coming from/going to. It isn't suddenly appearing from or disappearing to some "unknown nowhere". It's energy conservation.
In your system, heat left the system, and the system did some work on the environment I suppose (though this might be negligible). In any case, $Q<0$ and $W<0$, so it should be no surprise that $Delta U<0$. Energy has left your system (and has gone somewhere else), so the internal energy has decreased. Energy conservation is true, and it's present in the first law here.
answered 23 hours ago
Aaron StevensAaron Stevens
21.3k4 gold badges37 silver badges76 bronze badges
edited 22 hours ago
answered 23 hours ago
Aaron StevensAaron Stevens
21.3k4 gold badges37 silver badges76 bronze badges
answered 23 hours ago
Aaron StevensAaron Stevens
21.3k4 gold badges37 silver badges76 bronze badges
answered 23 hours ago
Aaron StevensAaron Stevens
21.3k4 gold badges37 silver badges76 bronze badges
21.3k4 gold badges37 silver badges76 bronze badges
6
$begingroup$
In engineering, a closed system is one in which no mass enters of leaves, but one which can exchange of heat and work with the surroundings. What you are envisioning as a closed system is what we call an "isolated system."
$endgroup$
– Chet Miller
22 hours ago
$begingroup$
@ChetMiller Ah ok, thanks. I have removed my parenthetical comment. In any case, the first law still applies to all systems.
$endgroup$
– Aaron Stevens
22 hours ago
$begingroup$
I accepted Bob Jacobsen's answer because it goes straight to the semantics and makes it clear at one shot. Chet Miller's comment under the original question also did. I still appreciate your answer and it also helps. The combination of both should be the final one. All the best and thanks again.
$endgroup$
– Alvaro Franz
15 hours ago
2
$begingroup$
@AlvaroFranz Glad I could help
$endgroup$
– Aaron Stevens
12 hours ago
add a comment |
6
$begingroup$
In engineering, a closed system is one in which no mass enters of leaves, but one which can exchange of heat and work with the surroundings. What you are envisioning as a closed system is what we call an "isolated system."
$endgroup$
– Chet Miller
22 hours ago
$begingroup$
@ChetMiller Ah ok, thanks. I have removed my parenthetical comment. In any case, the first law still applies to all systems.
$endgroup$
– Aaron Stevens
22 hours ago
$begingroup$
I accepted Bob Jacobsen's answer because it goes straight to the semantics and makes it clear at one shot. Chet Miller's comment under the original question also did. I still appreciate your answer and it also helps. The combination of both should be the final one. All the best and thanks again.
$endgroup$
– Alvaro Franz
15 hours ago
2
$begingroup$
@AlvaroFranz Glad I could help
$endgroup$
– Aaron Stevens
12 hours ago
6
6
$begingroup$
In engineering, a closed system is one in which no mass enters of leaves, but one which can exchange of heat and work with the surroundings. What you are envisioning as a closed system is what we call an "isolated system."
$endgroup$
– Chet Miller
22 hours ago
$begingroup$
In engineering, a closed system is one in which no mass enters of leaves, but one which can exchange of heat and work with the surroundings. What you are envisioning as a closed system is what we call an "isolated system."
$endgroup$
– Chet Miller
22 hours ago
$begingroup$
@ChetMiller Ah ok, thanks. I have removed my parenthetical comment. In any case, the first law still applies to all systems.
$endgroup$
– Aaron Stevens
22 hours ago
$begingroup$
@ChetMiller Ah ok, thanks. I have removed my parenthetical comment. In any case, the first law still applies to all systems.
$endgroup$
– Aaron Stevens
22 hours ago
$begingroup$
I accepted Bob Jacobsen's answer because it goes straight to the semantics and makes it clear at one shot. Chet Miller's comment under the original question also did. I still appreciate your answer and it also helps. The combination of both should be the final one. All the best and thanks again.
$endgroup$
– Alvaro Franz
15 hours ago
$begingroup$
I accepted Bob Jacobsen's answer because it goes straight to the semantics and makes it clear at one shot. Chet Miller's comment under the original question also did. I still appreciate your answer and it also helps. The combination of both should be the final one. All the best and thanks again.
$endgroup$
– Alvaro Franz
15 hours ago
2
2
$begingroup$
@AlvaroFranz Glad I could help
$endgroup$
– Aaron Stevens
12 hours ago
$begingroup$
@AlvaroFranz Glad I could help
$endgroup$
– Aaron Stevens
12 hours ago
add a comment |
$begingroup$
Conserved here doesn't mean that it is conserved only for your system (Not unless it's an isolated system). It is conserved for the whole universe. The total energy is constant. In performing any work or task , all you are doing is taking some energy from the surrounding and giving it to the system or vice versa. These 2 effects balance out or cancel each other if you consider the whole universe making thermodynamics "Perfectly balanced, as all things should be"
answered 3 hours ago
RandomAspirantRandomAspirant
1193 bronze badges
New contributor
RandomAspirant is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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$endgroup$
add a comment |
$begingroup$
Conserved here doesn't mean that it is conserved only for your system (Not unless it's an isolated system). It is conserved for the whole universe. The total energy is constant. In performing any work or task , all you are doing is taking some energy from the surrounding and giving it to the system or vice versa. These 2 effects balance out or cancel each other if you consider the whole universe making thermodynamics "Perfectly balanced, as all things should be"
answered 3 hours ago
RandomAspirantRandomAspirant
1193 bronze badges
New contributor
RandomAspirant is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
Conserved here doesn't mean that it is conserved only for your system (Not unless it's an isolated system). It is conserved for the whole universe. The total energy is constant. In performing any work or task , all you are doing is taking some energy from the surrounding and giving it to the system or vice versa. These 2 effects balance out or cancel each other if you consider the whole universe making thermodynamics "Perfectly balanced, as all things should be"
answered 3 hours ago
RandomAspirantRandomAspirant
1193 bronze badges
New contributor
RandomAspirant is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
Conserved here doesn't mean that it is conserved only for your system (Not unless it's an isolated system). It is conserved for the whole universe. The total energy is constant. In performing any work or task , all you are doing is taking some energy from the surrounding and giving it to the system or vice versa. These 2 effects balance out or cancel each other if you consider the whole universe making thermodynamics "Perfectly balanced, as all things should be"
answered 3 hours ago
RandomAspirantRandomAspirant
1193 bronze badges
New contributor
RandomAspirant is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered 3 hours ago
RandomAspirantRandomAspirant
1193 bronze badges
New contributor
RandomAspirant is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered 3 hours ago
RandomAspirantRandomAspirant
1193 bronze badges
answered 3 hours ago
RandomAspirantRandomAspirant
1193 bronze badges
1193 bronze badges
New contributor
RandomAspirant is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
RandomAspirant is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
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$begingroup$
It's conservation of total energy, not just the system's energy.
$endgroup$
– knzhou
yesterday
2
$begingroup$
In your example, the system would have to be the bottle AND the freezer, and the conservation of energy would imply that whatever heat was lost by the bottle must have been absorbed by the freezer. In general you want to consider closed systems, i.e. systems which do not interact with the environment (as the bottle taken alone is doing with the freezer).
$endgroup$
– Jxx
yesterday
1
$begingroup$
"conservation of energy", and talks about how internal energy equals heat and work transfer. This is wrong. It should be change in internal energy.
$endgroup$
– Aaron Stevens
23 hours ago
5
$begingroup$
This is an input - output = accumulation kind of thing. It's like a bank account, for which "conservation of money" exists. Deposits - Payments (checks) = change in bank balance. If money was disappearing, the FEDs would have to come in and arrest someone. In the first law, the change in internal energy is analogous to the change in bank balance. Heat added minus work done is analogous to deposits minus payments (although unlike a bank account, heat added and work done can both be positive or negative).
$endgroup$
– Chet Miller
23 hours ago
$begingroup$
Reminder: Answers go in the answers, not in comments. This is not directed at any one comment.
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6 hours ago