# Using the specific heat of any substance

1. Jul 18, 2010

### Tush

Ques 1) In determining and then using the specific heat of any substance:-
For solids and liquids, we usually assume that the sample is under constant pressure during the transfer, or at constant volume while the heat is absorbed. Then is it possible that the thermal expansion of the sample can be prevented by applying external pressure ?

Ques 2) Why it is that the specific heats under constant pressure and constant volume for any solid or liquid differ usually by no more than a few percent, where as gases have different values for their specific heats under constant pressure and constant volume ?

Ques 3) Generally , thermal expansion of gases is greater than that of solids and liquids . But this is true at any temperature (though the thermal expansion coefficient depends slightly on temperature) ? Is it due to the fact that the state of randomness for gas is much higher than that for liquid or gas.

Last edited: Jul 18, 2010
2. Jul 18, 2010

### Naty1

3. Jul 18, 2010

### Ali Inam

Re: Thermodynamics

Firstly,

YES, for the first question of yours and for the 2nd one, I would say that on liquids and solids, we dont have very large impacts of pressure if we compare that pressure to be implemented on gases.

Ah,

Not really sure about the 3rd question of yours !!

4. Jul 18, 2010

### Mapes

Re: Thermodynamics

Regarding question 3: solids and liquids don't expand much with temperature because their atoms are confined by the electrostatic bonds that hold these substances together. The atoms or molecules in gases aren't collectively bonded together, and so higher temperatures produce higher velocities and thus large increases in volume for systems maintained at constant pressure (and thermal expansion is defined as the increase in V with T at constant P).