Thermo(concept Q, pic included)- How does internal energy increase but

[thechamp]

Homework Statement

http://img694.imageshack.us/img694/9990/fig24a.jpg"

The scenario is, the water in the beaker = system 1. Everything else, including walls = system 2.

The bunsen burner heats the water in the beaker. dU or the change in internal energy of system 2 decreases. dT or the change in temperature of system 2 increases. How can this be possible?

The Attempt at a Solution

I thought about this for a while. My bad hunch and how I would answer this on a test is that...system 1 increases in temperature and heat is transferred from the bunsen burner to system 1. However, heat is transferred back into system 2 because the bunsen burner is only part of system 2. This is what happens as both systems try to reach equilibrium. I still don't know why the temperature of system 2 would increase though. To be honest, I don't even know what system 2 is referring to when in relation to temperature, is it referring to the average temperature of the surroundings (air, bunsen burner, atmosphere, etc.). I'm really confused as you can tell, someone please help!

 

[nate808]

Hello,

Thank you for sharing your thoughts and questions on this scenario. I can understand your confusion and I am happy to provide some clarification. Let's break down the situation and look at it from a thermodynamic perspective.

Firstly, when we talk about a system in thermodynamics, we are referring to a specific region or volume of space that we are interested in studying. In this scenario, we have two systems: system 1, which is the water in the beaker, and system 2, which includes everything else, such as the walls and the bunsen burner.

Now, let's consider what happens when the bunsen burner heats the water in the beaker. This is an example of heat transfer, which is the transfer of thermal energy from one system to another due to a temperature difference. In this case, the bunsen burner is at a higher temperature than the water, so heat will flow from the bunsen burner to the water until they reach thermal equilibrium, where the temperature of both systems is the same. This is why the temperature of system 1 (the water) increases as heat is transferred to it from system 2 (the bunsen burner).

However, as you correctly pointed out, heat is also being transferred back into system 2 as the water heats up. This is because system 2 is not just the bunsen burner, but also includes the walls of the beaker and the surrounding air. These components of system 2 are also in contact with the heated water, so heat will flow from the water to the walls and air until they reach thermal equilibrium. This is why the temperature of system 2 (the walls, air, etc.) increases as well.

Now, you may be wondering why the change in internal energy of system 2 decreases as the temperature increases. This is because internal energy is a measure of the total energy of a system, including both its thermal energy and its potential energy. As the temperature of system 2 increases, so does its thermal energy, but the potential energy of the system (such as the energy in the bonds between molecules) may decrease due to the expansion of the system as it heats up. This results in a net decrease in the internal energy of system 2.

I hope this explanation helps to clear up your confusion. If you have any further questions, please don't hesitate to ask. Keep up the great thinking and problem