Change in thermal energy of gas

In summary: This is completely possible.In summary, a gas is compressed from 600cm3 to 200cm3 at a constant pressure of 400kPa. At the same time, 100J of heat energy is transferred out of the gas. The change in thermal energy of the gas during this process can be calculated using the equation Eth=Q-Wgas, which gives a result of -60J. This means that the temperature of the gas drops during the compression process.
  • #1
Beastegargoyl
9
0

Homework Statement


A gas is compressed from 600cm3 to 200cm3 at a constant pressure of 400kPa . At the same time, 100J of heat energy is transferred out of the gas.

What is the change in thermal energy of the gas during this process?

Homework Equations


Express the answer in Joules.

Wgas=p(Vf-Vi)=p/\v


The Attempt at a Solution



400k(400cm.3)=p/\v

I came up with a wrong answer of 160 J. Any help would be appreciated.

Thanks,
Jared
 
Physics news on Phys.org
  • #2
You calculated the work done on the gas not the change in thermal energy. What equation gives you the change in thermal energy of a gas?
 
  • #3
I found the correct equation to use is Eth=Q-Wgas.

Alright. Eth=100J-160J = 60 J is that answer required to be in a positive or negative 60J?

Thanks,
Jared
 
Last edited:
  • #4
Using the first law is the correct thing to do. It says ΔE = Q - W. You need to pay attention to the symbols and their signs. Is Q positive or negative? What about W? Positive or negative and why?
 
  • #5
BTW, the sign on W is purely arbitrary. Thermodynamics has adopted the convention that W should be considered from the point of view of the gas: that is, the work done by the gas is W.
 
  • #6
I am pretty certain the answer is -60J. Although, I don't feel confident that you can have a negative thermal energy change.

@ideasrule- I don't quite understand what you mean?
 
  • #7
Remember that the internal energy depends on the temperature only. A negative thermal energy change means that the temperature drops.
 

FAQ: Change in thermal energy of gas

1. How is the change in thermal energy of gas related to temperature?

The change in thermal energy of gas is directly proportional to the temperature. As the temperature of a gas increases, the thermal energy also increases and vice versa. This is because temperature is a measure of the average kinetic energy of the gas molecules, and an increase in kinetic energy results in an increase in thermal energy.

2. What factors can cause a change in thermal energy of gas?

There are several factors that can cause a change in thermal energy of gas, such as changes in temperature, pressure, volume, and the number of gas molecules. Additionally, the type of gas and its specific heat capacity can also affect the change in thermal energy.

3. How is the change in thermal energy of gas calculated?

The change in thermal energy of gas can be calculated using the formula Q = mcΔT, where Q is the change in thermal energy, m is the mass of the gas, c is the specific heat capacity of the gas, and ΔT is the change in temperature.

4. Does a change in thermal energy always result in a change in temperature?

No, a change in thermal energy does not always result in a change in temperature. This is because the change in temperature depends on the specific heat capacity of the gas. If the gas has a high specific heat capacity, it can absorb a large amount of thermal energy without a significant increase in temperature.

5. What is the relationship between the change in thermal energy of gas and work done?

The change in thermal energy of gas can also be related to the work done on or by the gas. When work is done on a gas, such as compressing it, the gas molecules gain kinetic energy resulting in an increase in thermal energy. On the other hand, when work is done by a gas, such as expanding, the gas molecules lose kinetic energy resulting in a decrease in thermal energy.

Similar threads

Replies
5
Views
816
Replies
4
Views
2K
Replies
14
Views
7K
Replies
3
Views
1K
Replies
8
Views
1K
Replies
2
Views
3K
Replies
9
Views
2K
Back
Top