Problem: Which of the following statements is(are) true?(a) The enthalpy of vaporization is usually larger than the enthalpy of fusion because it takes less energy per mole to separate particles to form a gas than it takes to melt the same substance.(b) When a substance undergoes a phase change, the temperature remains constant and the added energy is simply lost to the surroundings.(c) As energy is added to a substance at the melting point, the substance is in equilibrium between its solid and liquid phases.(d) Statements (a), (b), and (c) are all false.(e) Only statements (b) and (c) are true.

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We are asked which of the following statements is(are) true regarding phase change. 


Analyze each statement: 

(a) The enthalpy of vaporization is usually larger than the enthalpy of fusion because it takes less energy per mole to separate particles to form a gas than it takes to melt the same substance.

  • This statement is FALSE since if we look at a table of standard values, enthalpy of vaporization and fusion, enthalpy of vaporization is almost always higher. 


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Problem Details

Which of the following statements is(are) true?

(a) The enthalpy of vaporization is usually larger than the enthalpy of fusion because it takes less energy per mole to separate particles to form a gas than it takes to melt the same substance.

(b) When a substance undergoes a phase change, the temperature remains constant and the added energy is simply lost to the surroundings.

(c) As energy is added to a substance at the melting point, the substance is in equilibrium between its solid and liquid phases.

(d) Statements (a), (b), and (c) are all false.

(e) Only statements (b) and (c) are true.