Heat Transfer and Phase Changes

This video tutorial covers a comprehensive problem involving a cooling curve for isopropanol. It explains the process of cooling a 50-gram sample from vapor at 90°C to a solid at -100°C, detailing the heat removal required at each phase change and temperature change. The tutorial breaks down the problem into five regions, each representing a different stage of the cooling process, and provides step-by-step calculations using specific heat capacities and phase change enthalpies. The video concludes by summing the total heat removed, emphasizing the importance of unit consistency in calculations.

What is the initial state of the isopropanol sample in the problem?

• Liquid at 82.6°C

• Solid at 0°C

• Solid at -100°C

• Vapor at 90°C

What does the plateau at 82.6°C on the cooling curve represent?

• Sublimation point

• Boiling point

• Condensation point

• Melting point

Which equation is used to calculate the heat change in region 1?

• q = nΔHfus

• q = nΔHvap

• q = mcΔT

• q = mL

During the phase change in region 2, which property is used in the calculation?

• Molar mass

• Heat of fusion

• Heat of vaporization

• Specific heat capacity

What is the specific heat capacity used for the liquid phase in region 3?

• 4.18 J/g·K

• 0.90 J/g·K

• 1.54 J/g·K

• 2.68 J/g·K

In region 4, what is the phase change occurring?

• Liquid to solid

• Solid to liquid

• Liquid to vapor

• Vapor to liquid

What is the final temperature the solid isopropanol is cooled to in region 5?

• -89°C

• -50°C

• -100°C

• 0°C

Why is it necessary to convert grams to moles in the calculation for region 5?

• To simplify the calculation

• To increase accuracy

• To avoid using Kelvin

• To match the units of specific heat capacity

What is the main issue addressed when summing up the total heat removed?

• Mass measurement

• Unit consistency

• Phase identification

• Temperature conversion

What is the final step in calculating the total heat removed from the sample?

• Adding all heat values in joules

• Converting all values to kilojoules and summing them

• Calculating the average heat

• Subtracting the smallest heat value