How does the enthalpy of fusion change from solid to liquid state?

Is the enthalpy of fusion positive or negative when going from solid to liquid?

The enthalpy of fusion is:
a. positive
b. negative

Answer:

The enthalpy of fusion is positive when transitioning from a solid to a liquid state.

The enthalpy of fusion is positive when going from a solid to a liquid state. This indicates that heat is absorbed during the endothermic process of fusion. The strength of interparticle forces in the substance also influences the enthalpy of fusion and melting point.

Enthalpy of fusion, denoted as ΔHfus, refers to the amount of heat needed to convert a substance from its solid state to its liquid state. It is a type of enthalpy change that occurs during the phase change of a substance. When transitioning from a solid to a liquid state, the process is endothermic, meaning it absorbs heat. This results in a positive enthalpy change (ΔHfus) during fusion or melting.

For example, the enthalpy of fusion of ice is +6.0 kJ/mol as it changes from solid ice to liquid water at 0 °C. This positive value indicates that energy is absorbed during the process. The strength of attractive forces between particles in a crystalline solid also influences its enthalpy of fusion and melting point. Crystals with weak attractive forces melt at lower temperatures, while those with stronger forces require higher temperatures.

Therefore, the enthalpy of fusion is positive when transitioning from a solid to a liquid state, as heat is absorbed during the endothermic fusion process, leading to an increase in the system's energy. The melting point and enthalpy of fusion are greatly influenced by the interparticle forces present in the substance.