Define Enthalpy

[Ashley Hiti 1K]

I am having a little trouble determining exactly what enthalpy is. Specifically it's relation to heat. How would you define enthalpy?

[madison_bang_1L]

Enthalpy measures the loss/gain of energy during heat transfer at constant pressure. Since the system is open to the atmosphere, the volume can be adjusted and expansion/compression work is done.
This can be mathematically derived from deltaH = deltaU + P(deltaV).
Since deltaU = q + w --> deltaH = (q+w) + P(deltaV).
Since w = -P(deltaV) --> deltaH = q + (-P(deltaV) + P(deltaV).
These values cancel out and leave deltaH = q.

[Cadence Chang]

Hi there! Enthalpy is the total heat content in a system. It includes energy between bonds; it's basically all the internal energy of a system. Meanwhile, heat is the energy in transit throughout a system. So enthalpy is measuring the amount of heat. Hope this helps!

[205783236]

enthalpy is the change in heat from a system. a positive enthalpy means that energy was put into the system (ie. to break bonds, endothermic) a negative enthalpy means that energy was released (ie. bonds made, exothermic)

[Rebecca Preusch 2C]

Positive delta H is an addition of energy (endothermic) and negative delta H is a release of energy (Exothermic). Therefore delta h corresponds to a release/input of heat depending on its sign.

[Sarah Hong 2K]

Enthalpy is the change in heat. It is represented by delta H. A positive enthalpy/delta H is an endothermic reaction and a negative enthalpy/delta H is an exothermic reaction.

[Abby 2B]

Enthalpy is the heat content of a system, and an enthalpy change is the heat released or absorbed by a reaction.