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The enthalpy of vaporization is greater than the enthalpy of fusion because during a phase change the molecules are separated and the energy required to completely separate the molecules from a liquid to gas is much greater that if you were just to reduce their separation when converting from solid to liquid.
It may help to visualize the molecules that make up a solid, liquid and gas. When turning a solid to a gas, the molecules are more freely moving, but still packed together. However, when you turn a liquid into a gas, you are energizing the molecules so that they are quickly bouncing around completely free.
Water in its liquid state has strong intermolecular force (hydrogen bonding), but water in its vapor phase has almost no intermolecular force. Thus, it takes a lot of energy to break the hydrogen bonds for water in liquid phase to turn to water in vapor phase. For fusion, the intermolecular forces aren't completely destroyed, but the intensity of the force is decreased. It takes less energy to weaken the force to convert water in solid state to water in liquid state.
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