# Difference between enthalphy and heat?

1. Sep 27, 2005

### asdf1

in my thermodynamics textbook, enthalphy=U+PV
and (delta)heat=(delta)U+(delta)PV
those 2 look the same...
can anybody explain the difference?
@@

2. Sep 27, 2005

### Q_Goest

Hi asdf1. Take a look at your book again, I think you've taken it out of context. For example, flow through a pipe where heat is added or removed between two points in the pipe is a process in which the heat added/removed is equal to the enthalpy change in the fluid. On the other hand, for the situation where heat is added to a sealed container (ex: a pressurized tank), the amount of heat added or removed is equal to the change in the fluid's internal energy.

3. Oct 2, 2005

### hotvette

I was taught that enthalpy was a property of a substance. Heat is a transport phenomenon only (i.e. transfer of energy) and that there is no such property as heat.

4. Oct 2, 2005

### GCT

at constant pressure with only expansion work the enthalpy of the substance does equal to the heat pertaining to the situation, that is $$q_p$$

5. Oct 3, 2005

thanks!!! :)