# Enthalpy

Thermochemistry | The Nature of Energy.

Tip: This isn't the place to ask a question because the teacher can't reply.

1 of 3 videos by Dr. Hayek

## Key Questions

• Enthalpy (H) is the heat content of a system at constant pressure. The heat that is absorbed or released by a reaction at constant pressure is the same as the enthalpy change, and is given the symbol ($\Delta$H) . Unless otherwise specified, all reactions in this material are assumed to take place at constant pressure. Therefore, there is a connection between enthalpy and the first law of thermodynamics, where energy cannot be created nor destroyed.

Here is a video which discusses how to calculate the enthalpy change when 0.13g of butane is burned.
Video from: Noel Pauller

• It cannot be measured.

Enthalpy is not a physical property. Enthalpy depends on temperature and it's an energy content measurement. Pipes burst because of high temperatures and pressures, not enthalpies. Enthalpy can't do a physical change because for there to be an enthalpy change, there should be a change in a thermal physical property named temperature. The day you hear someone saying that I have been hit with a stone and the stone had high enthalpy, then maybe we can measure enthalpy physically.

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