Enthalpy and Phase Changes

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Presentation transcript:

Enthalpy and Phase Changes When a substance goes through a phase change all the energy is used to change phase…..there is no temperature change (increase or decrease). Therefore we can not use the specific heat formula which needs a temperature change

Heats of Fusion and Vaporization Heat of Fusion (Hf) is the energy required to melt a solid and change it to a liquid (or the reverse change a liquid to a solid….just a different sign….energy flow) Heat of Vaporization (Hv) is the energy required to change a liquid into a gas (or the reverse, change a gas into a liquid….just a different sign for q)

Graphical Representation of Enthalpy