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Phase changes and enthaplies

Posted: Thu Jan 31, 2019 11:04 am
by charlotte_jacobs_4I
How are phase changes and enthalpies related? Does it have to do with exothermic and endothermic reactions?

Re: Phase changes and enthaplies

Posted: Thu Jan 31, 2019 11:12 am
by Courtney Quan 1C
Enthalpy is defined as the amount of heat released or absorbed at a constant pressure. You are correct in speculating that it is related to exothermic (releasing energy) and endothermic (requires heat) reactions, and that relates to phase changes. In a phase change, energy is required to break the chemical bonds so that a new phase may be attained. In the phase transitions we have discussed in class (vaporization, melting/fusion, sublimation), the reactions are endothermic and require heat.

Re: Phase changes and enthaplies

Posted: Fri Feb 01, 2019 2:35 pm
by fgalasso1b
Enthalpy is the heat absorbed/released in a reaction. Phase changes are a physical reactions so they also have enthalpies.

Re: Phase changes and enthaplies

Posted: Fri Feb 01, 2019 2:44 pm
by JadeSebti1L
Remember that Lavelle said that enthalpy is a state function, meaning its value depends on the phase of the substance which you are referring to. However, enthalpy change is a two-state function so wouldn't even be considered a state function.