Chapter U5.99, Problem 2E

Interpretation Introduction

Interpretation: Heat of vaporization is needs to be explained.

Concept Introduction: The Heat of Vaporization is the quantity of heat that requires to be consumed to vaporize an appropriate amount of liquid at a constant temperature. By comparing vapor and liquid state solutions, the steam's kinetic energy is found to be higher than the fluid's kinetic energy.

Answer to Problem 2E

Heat needed to change 1 gram of a substance from a liquid into a gas is called the heat of vaporization.

Explanation of Solution

When a substance changes phase from solid to liquid or liquid to gas, a certain amount of energy must be supplied to overcome the molecular or ionic attractions between the particles. This energy is changing the solid into the liquid or the liquid into a gas, without changing the temperature. The value of heat of vaporization of water is $539\text{cal/g}$ that means water needs this amount of energy to change from liquid to gas.

Conclusion

Heat of vaporization is the energy needed to change a substance from liquid to gas.