Phase Changes: Heat Is Added to a Pure Substance in a Closed

question 109

Multiple Choice

Phase changes: Heat is added to a pure substance in a closed container at a constant rate. The figure shows a graph of the temperature of the substance as a function of time. If L_f = latent heat of fusion and L_v = latent heat of vaporization, what is the value of the ratio L_v / L_f for this substance?

• A) 5.0
• B) 4.5
• C) 7.2
• D) 3.5
• E) 1.5

---

Definitions:

High-Low Method

An accounting method used to estimate the fixed and variable components of a cost based on the highest and lowest levels of activity.

Variable Maintenance Cost

Costs that change in proportion to the operational activity of a company, such as repairs and maintenance expenses that vary with usage.

Mixed Cost

A cost containing both variable and fixed cost elements, changing in total with activity level but not proportionately.

Direct Labor Hours

The total time workers spend producing a product or providing a service, directly tied to the production process.