enthalphy of fusion for h2o is 6.01 kg/mol and enthalpy of vaporization is 40.7 kj/mol. why...

enthalphy of fusion for h2o is 6.01 kg/mol and enthalpy of vaporization is 40.7 kj/mol. why are they so different?

Expert Solution

Molecules are closely packed in solids than liquid so the intermolecular force of attraction is greater than that in liquid. In Solid substance, molecules have not much space to move. In liquid substance, molecules have space to move. In gas, molecules are far apart with almost no attractive forces.

While change the phase of solid to liquid

Heat required to increase in the molecular kinetic energy to lower the intermolecular force of attraction among its molecules.

While change the phase of liquid to gas

Heat required to increase in the molecular kinetic energy to lower or to negligible the intermolecular force of attraction among its molecules.

energy required to convert from liquid to gas is much greater than that of solid to liquid. Hence enthalpy of vaporization for H2O is greater than enthalpy of fusion for H2O

energy required to change the phase is potential energy not kinetic energy. Phase change occurs at constant temperature. Kinetic energy depends on the temperature and at constant temperature, kinetic energy is also constant. This potential energy is required to break the bonds so that the change in phase occur.

Amanda K answered 2 years ago

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