Thermodynamics trick question?

In summary, the conversation discusses a seemingly contradictory situation where an empty bottle on a windowsill has a higher temperature on one side than the other, despite being in thermal equilibrium with the outside and the house. The different ways heat can be transferred (conduction, convection, and radiation) are considered, with the conclusion being that the difference in temperature could be due to the bottle being turned around or receiving more solar radiation. However, this solution is disputed due to the assumption that the bottle must be in thermal equilibrium with the outside.
  • #1
Valhalla
69
0
An empty bottle sits on a windowsill next to a closed window inside a house. The outside and the house are in thermal equilibrium. Yet, the side of the bottle OPPOSITE the window has a higher temp then the side touching the window. How can this be? (Assume nothing is touching the bottle except the windowsill)

Well, this is what I reasoned so far. There is only 3 ways that heat can be transferred, conduction, convection, and radiation. There is no conduction that is heating the hotter side because there is nothing touching it. It can't be convection b/c the room is in thermal equilibrium with the outside. It has to be the fact that something in side the room is radiating energy onto it.

Does this make sense? Any other ideas?
 
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  • #2
possibly the sun's energy
 
  • #3
Valhalla said:
An empty bottle sits on a windowsill next to a closed window inside a house. The outside and the house are in thermal equilibrium. Yet, the side of the bottle OPPOSITE the window has a higher temp then the side touching the window. How can this be? (Assume nothing is touching the bottle except the windowsill)

Well, this is what I reasoned so far. There is only 3 ways that heat can be transferred, conduction, convection, and radiation. There is no conduction that is heating the hotter side because there is nothing touching it. It can't be convection b/c the room is in thermal equilibrium with the outside. It has to be the fact that something in side the room is radiating energy onto it.

Does this make sense? Any other ideas?
Is there any air in the room? If there is air in the room, I don't see how the bottle can be at different temperatures and still have the air in the room at thermal equilibrium (which must mean all at the same temperature).

AM
 
  • #4
An empty bottle sits on a windowsill next to a closed window inside a house. The outside and the house are in thermal equilibrium. Yet, the side of the bottle OPPOSITE the window has a higher temp then the side touching the window. How can this be? (Assume nothing is touching the bottle except the windowsill)

This question is bad. (1) How can you assume nothing is touching the bottle except the windowsill, yet its touching the window at the same time. (2) If everything is in thermal equilibrium, as AM has already said, it MUST be isothermal everywhere. (3) The anwser, I think, which is still crap, is that the side touching the window transfers heat due to conduction of the glass, and the side exposed to air gets conduction and convection. So there is a temperature differential. But this is only during the process that it heats up to room temp. Afterwards, it will be isothermal everywhere. Another possibility is that the side nearer the window receives more solar radiation than the other side. But this would be such a small difference. If the bottle is clear, the radiation should pass through both sides. Eh, I don't know what to tell you.
 
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  • #5
Ok this is the solution that was given...

The bottle has been just turned around.


How can this even be assumed from the question? It states the room was in thermal equilibrium with the outside therefore via the zeroth law the bottle has to be in thermal equilibrium too! I agree this question is horrible.
 

1. What is the first law of thermodynamics?

The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transferred or converted from one form to another.

2. Can heat flow from a colder object to a hotter object?

No, according to the second law of thermodynamics, heat can only flow spontaneously from a hotter object to a colder object. This is because heat transfer always occurs in the direction of increasing entropy.

3. What is the difference between an open and closed thermodynamic system?

An open thermodynamic system exchanges both matter and energy with its surroundings, while a closed system only exchanges energy. In an isolated system, neither matter nor energy can be exchanged with the surroundings.

4. Does the third law of thermodynamics apply to all systems?

No, the third law of thermodynamics only applies to systems at absolute zero temperature. It states that the entropy of a perfect crystal at absolute zero is zero.

5. Can you give an example of a thermodynamics trick question?

An example of a thermodynamics trick question is "Which weighs more: a pound of feathers or a pound of bricks?" The trick is that both objects weigh the same because a pound is a unit of mass, not weight. In thermodynamics, weight is not a factor when considering the transfer of energy.

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