# Homework Help: Potetial energy change during heating

1. Oct 31, 2012

### sgstudent

1. The problem statement, all variables and given/known data
when heating i learned that only the kinetic energy component of internal energy increases. However, I also learned that potential energy is related to distance between the particles. So when i heat some solid and it expands does it mean the potential energy has changed as well? I don't think that is the reason for the expansion.

2. Relevant equations
none

3. The attempt at a solution
i understand that it moves faster but i don't think the amplitude of vibration should increase as i don't think the potential energy increases.

Thanks for the help!

2. Oct 31, 2012

### grzz

Maybe you read the above in a context where an ideal gas is assumed. In an ideal gas it is assumed that there are no intermolecular forces and so there is no potential energy.

3. Oct 31, 2012

### sgstudent

But what about solids? When I heat iron it expands but its potential energy should not increase so what's letting it expand?

4. Oct 31, 2012

### grzz

If the iron expands its potential energy increases.

5. Oct 31, 2012

### sgstudent

So even as it heats up the potential energy changes as well? That's possible?

6. Oct 31, 2012

### grzz

If the iron expands, the interatomic distances must have increased. But atoms attract each other. So the potential energy must increase.

7. Oct 31, 2012

### sgstudent

oh so when we calculate Q=mcΔT it is not complete since we have not taken potential energy into account?

8. Oct 31, 2012

### grzz

When the temperature of a solid is increased, both internal KE and internal PE increase and the specific heat capacity c of a solid must take care of both these increases.

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