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# Constant temperature change in a system

## Constant temperature change in a system

(OP)
Hi,
i had always believed that when heat is transfered from surrounding to a system, temperature must respond within the system (an increase in this case). but recently i came across an example in a text where heat was added to a system and temperature remained constant. could it be that i have had a wrong notion all this while?

### RE: Constant temperature change in a system

Yes. Your notion was wrong. For example consider melting of Ice or boiling of water.

In both cases, you should supply latent heat to change the phases but temperature remains constant.

### RE: Constant temperature change in a system

(OP)
I am aware of latent heat, i forget to state that the heat added was not latent. Visible heat tranfer to a gas that is what i am talking about here.

### RE: Constant temperature change in a system

An ideal gas (pV = nRT) can be expanded reversibly and isothermally by the absorption of heat. Since the internal energy of an ideal gas cannot change in an isothermal process, dU= 0 = dQ + dW. For a mechanical reversible non-flow process Q = -W = RTln(V2/V1), since P1/P2 = V2/V1, one can also write Q = -W = RT ln(P1/P2).

### RE: Constant temperature change in a system

visible heat that is a new one. unless you are alluding to real gas supercritical behavior, 25362 comments are right on.

### RE: Constant temperature change in a system

(OP)
thanks to all who contributed to clarify me. Especially 25362 and to HACKSAW , i actually meant sensible heat thanks for the observation. hoping we could share knowledge the more in this forum.

### RE: Constant temperature change in a system

any ideas on how estimate the specific of molten iron at 1000 m hydrostatic head?

### RE: Constant temperature change in a system

i'd like to help, but what 'specific' are u looking for?

;)

### RE: Constant temperature change in a system

First of all I am very sorry to trivialize the original post and I agree that I should have a little bit high estimation.

25362 is correct asusual. But that is possible (and is evident from his equation) if and only if work is done by the system external to it.

Once again I am sorry.

### RE: Constant temperature change in a system

(OP)
to hacksaw, ur question is not clear. specific what of iron?
to quark: u are really a nice guy. u need not apologise, i completely understand.

### RE: Constant temperature change in a system

the constant pressure and constant volume specific heat

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