Heat of Transformation

Heat of Transformation - The heat required to change the...

This preview shows page 1. Sign up to view the full content.

Heat of Transformation When heat is added to a solid or a liquid, the temperature of the sample does not necessarily rise. During a phase change (melting, boiling) heat is added to the sample without an increase in temperature. The amount of heat transferred per mass unit during a phase change is called the heat of transformation (symbol L) for the process. The amount of heat needed/released is given by where m is the mass of the sample. Problem 28P What mass of steam of 100 ϒ C must be mixed with 150 g of ice at 0 ϒ C, in a thermally insulated container, to produce liquid water at 50 ϒ C ? We start with calculating the heat required to transform 150 g of ice at 0 ϒ C to 150 g of liquid at 0 ϒ C. The heat of transformation of water is 333 kJ/kg (see Table 20-2, page 555). The transformation of ice into water therefore requires a total heat given by
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: The heat required to change the temperature of 150 g of water from 0 ϒ C to 50 ϒ C is given by The total heat that needs to be added to the system is therefore equal to 81.5 kJ. This heat must be supplied by the steam. Heat will be released when the steam is transformed into liquid, The heat of transformation for this process is 2260 kJ/kg. Suppose the mass of the steam is m. The total heat released in the conversion of steam into water is given by The heat released when the steam cools down from 100 ϒ C to 50 ϒ C is given by The total heat released by the cooling of the steam is therefore equal to 2470 m kJ. The total heat required is 81.5 kJ, and we therefore conclude that the mass of the steam must be equal to 33 g....
View Full Document

{[ snackBarMessage ]}

What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern