- vCommons Home
- Enthalpy

# Enthalpy

The **Enthalpy** calculator compute the enthalpy energy based on the internal energy, pressure and volume.

**INSTRUCTIONS:** Choose units and enter the following:

- (
**U**) This is the internal energy - (
**p**) This is the pressure - (
**V**) This is the volume

**Enthalpy(H):** The calculator returns the enthalpy in joules. However this can be automatically converted to compatible units via the pull-down menu.

#### The Math / Science

The **enthalpy ^{[1]}** equation is always associated with the first law of thermodynamics

^{[3]}, which states that energy can not be created or destroyed, thus it is to calculate the energy released or absorbed by the system. The system

^{[4]}is what we're interested in (such as the substance or matter), the environment around the system is called it's surroundings

^{[5]}. Energy is transferred between the two and the enthalpy equation is the way to measure the energy change in the form of heat

^{[6]}.

The **enthalpy equation** is defined by

** H = U + P•V**

where:

**H**is the**enthalpy**(Joules)**U**is the**internal energy**(Joules)**P**is**pressure**(pascals)**V**is**volume**(m^{3},mL)

The **enthalpy equation** is a state function, which means its dependent on its variables, specifically temperature, pressure and internal energy^{[7]}. If temperature and pressure were to be kept constant the equation will be ΔH=ΔU+PΔV. From this equation we can see that the enthalpy is dependent on the change of volume and internal energy. If pressure is kept constant than the equation becomes ΔH=q, from this we can observe whether the system absorbs or releases heat

## Related Topics

## Supplement Material

- CrashCourse:
- Khan Academy:
- HyperPhysics:

## References

[1]https://en.wikipedia.org/wiki/Enthalpy

[2]Whitten, et al. 10th Edition. Pp.577

[3]https://en.wikipedia.org/wiki/First_law_of_thermodynamics

[4]https://en.wikipedia.org/wiki/Thermodynamic_system

[5]https://en.wikipedia.org/wiki/Thermodynamic_system

[6]https://en.wikipedia.org/wiki/Heat

[7]http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/inteng.html

**Enthalpy**, is listed in 2 Collections.