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SirazTV
United States209 Posts
On April 19 2011 07:38 Chill wrote: But even if it's the same, the zeroth law doesn't tell us that. But then there is not enough information to answer the question. Lack of information =/= false. | ||
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Dragar
United Kingdom971 Posts
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Myles
United States5162 Posts
On April 19 2011 07:46 SirazTV wrote: Lol, you are completely missing the point of the Zeroth Law of thermodynamics......... The point is that the liquid, glass, mercury, and air are all in equilibrium with each other. Without the zeroth law even if the liquid and glass were in equilibrium and the glass and mercury were in equilibrium. The liquid and mercury would not be in equilibrium. Without this it would be impossible to measure temperature. Look, just because in grade school math A=B, B=C ==> A=C does not mean it is always the case. Huh? I think you're reading a bit too much into the question. It's says nothing about anything being in equilibrium. It talks about two bodies, the thermometer and the liquid. Talking about the components of the thermometer, or the air or the glass is adding extra info that isn't given. As pointed out by others, we have no idea at what temperature anything is at or how long the things have been in contact. The whole question is does Zeroth law tell you that the two objects are in equilibrium, which is no. | ||
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APurpleCow
United States1372 Posts
On April 19 2011 07:48 SirazTV wrote: But then there is not enough information to answer the question. Lack of information =/= false. Nope. You are not answering true/false as to whether or not the temperature is the same, but to whether or not the zeroth law says it is. Since there's no third system, it doesn't, so the answer is false. | ||
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palanq
United States761 Posts
this question is not poorly written nor is it open to interpretation. | ||
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Dragar
United Kingdom971 Posts
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Chill
Calgary25991 Posts
On April 19 2011 07:48 SirazTV wrote: But then there is not enough information to answer the question. Lack of information =/= false. Read the question and then read the answers. Lack of information does equal false in this case. I don't know how people are confusing this question. It doesn't even state the thermometer is at equilibrium with the liquid, just that it's submerged. The liquid could be ice water and the thermometer could be a hundred degrees. That's not at equilibrium so the zeroth law doesn't tell us anything in this situation. | ||
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Dragar
United Kingdom971 Posts
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okum
France5778 Posts
On April 19 2011 07:48 SirazTV wrote: But then there is not enough information to answer the question. Lack of information =/= false. Usually a true/false question is understood as asking whether a proposition is a tautology, i.e. whether it is true for every allowed value of the variables involved. | ||
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Yurie
12009 Posts
Since we can't do that (answering afterwards) I would have to go with false due to the reasons others have stated. Not enough information equals false. Another option would be to expand upon the question options, tick false and then give a reason so you show you understood the material but that the question tricked you if you answer incorrectly. (This doesn't work if it is scanned and just checks the area for the answer and automagically corrects it afterwards.) | ||
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Jonoman92
United States9106 Posts
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n.DieJokes
United States3443 Posts
Edit: Clarification: An important corollary of the zeroth law is as follows "Two systems are in thermal equilibrium if and only if they have the same temperature" Second Edit: I went back and checked my text just to make sure, they mention this exact example (I assume its the standard example), the only reason a thermometer is useful is because it measures its own temperature which, by zeroth law, is the temperature of its surrounding. Ignore the formal 3 bodies definition, that's not whats important. Third Edit: Granted the question is ambiguous as whether or not the thermometer is in equilibrium with the water but, because it doesn't say one way or another, we can logically assume that it is since we're talking about a thermometer. Its only use is when its in equilibrium and it reaches that relatively quickly, I think the other posters in this thread are over thinking it | ||
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Dragar
United Kingdom971 Posts
 I don't think it's a very good question but you are probably right, that is what the teacher is trying to get at with the question. | ||
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Vertig0
United States196 Posts
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Grobyc
Canada18410 Posts
On April 19 2011 06:55 KlaCkoN wrote: Assuming that the system is in thermal equlibrium yes. However the question says nothing about that so the correct answer should be "not necessarily"? I dunnu. Yeah this is what I figure as well. | ||
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Chimpalimp
United States1135 Posts
I always hated them. | ||
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n.DieJokes
United States3443 Posts
On April 19 2011 09:04 Dragar wrote: Ah, but DieJokes, the thermometer only has the temperature of the surroundings thanks to the first and second laws. I don't think it's a very good question but you are probably right, that is what the teacher is trying to get at with the question. Well, not directly right? As I understand it (I'm a first year chem major) the zeroth law came after the other three so it was discovered using the intuitive concepts that followed from the but it is fundamental to all three of them (hence zeroth). So sure you could come up with that from the first two, but the first two don't actually say that. On April 19 2011 09:27 Vertig0 wrote: Chill nailed it. The question isn't whether the thermometer and liquid are the same temperature, it's whether the Zeroth Law tells you that they are, which it clearly doesn't. The zeroth law does tell you this, but not directly from the formal definition. If you look in your texts they'll describe exactly this situation as an application of the zeroth law, a cursory glance at the wiki isn't sufficient (not to say you did that, but I think some other people in the thread have; please don't take any of this personally I don't mean it to be) | ||
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Dragar
United Kingdom971 Posts
On April 19 2011 10:04 n.DieJokes wrote: Well, not directly right? As I understand it (I'm a first year chem major) the zeroth law came after the other three so it was discovered using the intuitive concepts that followed from the but it is fundamental to all three of them (hence zeroth). So sure you could come up with that from the first two, but the first two don't actually say that. Sort of directly. Thermometers work (in the sense that they reach the same temperature as their surroundings) because of the first and second laws. (I think the simplest way to put is is that the first law tells us how heat and entropy are related, and the second law tells us how entropy behaves - the combination allowing us to deduce how heat will flow between the thermometer and its surroundings when out of equilibrium.) The zeroth law is indeed fundamental, as it gives you a meaning behind temperature (equilibrium) in the first place. | ||
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n.DieJokes
United States3443 Posts
On April 19 2011 10:10 Dragar wrote: Sort of directly. Thermometers work (i.e. they reach the same temperature as their surroundings) because of the first and second laws. The zeroth law is indeed fundamental, as it gives you a meaning behind temperature in the first place. I get what you're saying, but the zeroth tells us that they will have exactly the same temperature at equilibrium; you can't get that directly from the first or more importantly the second law. Edit: That seems ambiguous; the second law says energy is conserved in the system and acts in such a way as to decrease potential energy. So from this the thermometer will heat or cool depending on its surrounds and vice versa. It's the zeroth law that tells us that this system reaches equilibrium if and only if they have exactly the same temperature. It doesn't matter what the materials are, they will reach the same temp. | ||
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jenzebubble
United States183 Posts
On April 19 2011 07:46 SirazTV wrote: Lol, you are completely missing the point of the Zeroth Law of thermodynamics......... The point is that the liquid, glass, mercury, and air are all in equilibrium with each other. Without the zeroth law even if the liquid and glass were in equilibrium and the glass and mercury were in equilibrium. The liquid and mercury would not be in equilibrium. Without this it would be impossible to measure temperature. Look, just because in grade school math A=B, B=C ==> A=C does not mean it is always the case. I can think of no system where using the operator =, A, B and C the way that you have and with the parameters that you have, that a person would be unable to infer a relationship between A and C. Perhaps choose your operators better next time you decide to be a smarmy ass. | ||
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