# 2011 1011 _Heat Transfer Worksheet_

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```					HEAT TRANSFER                                              Name: _______________________________ Block: _____
College Prep                                              Partners: ________________________________________

THE CALORIC
Heat was originally thought to be a kind of fluid property that objects could have. We now know that heat is the energy
of molecules and atoms. There are two ways that heat can move from one object to another, and a third for moving
through a fluid. Heat can move through direct contact (conduction), as a form of electromagnetic radiation (radiation),
or as a current through a fluid (convection). We will only focus on conduction.

HEAT TRANSFER
We are also going to make the assumption that heat is only moving between two substances (usually). While that’s not
100% accurate, we can assume that the objects we wish to study are insulated from the rest of the universe. This is a
pretty good assumption when you make a measurement in an insulated environment – like a polystyrene cup / cooler /
package – and the measurements are done in a short amount of time. It sounds complicated, but what we are trying to
do is to simplify things, or, rather, to control variables.

If we place two samples of two different temperatures into an insulated environment, what will happen to the two
samples? _________________________________________________ If we go to all of the trouble of creating this
isolated environment, we can carefully measure how the heat moves between the two samples.
If you place 50.0g of 350K water into 50.0g of 300K water, what is the Tf? _____________________________________
If you place 150.0g of 350K water into 50.0g of 300K water, what is the Tf? _____________________________________
If you place 50.0g of 350K water into 150.0g of 300K water, what is the Tf? ____________________________________
When you add any two substances together, the hot one will cool down, and the cool one will warm up, until they are
both at the same temperature (we call this thermal equilibrium). But, when you add two different substances together,
you have to know the specific heat for each substance. They will still come to thermal equilibrium, but the change in
temperatures will be different. The heat lost by one will be the heat gained by the other (qlost = -qgained). If you know the
initial temperatures, final temperature, masses, and you know the specific heat of one of the samples, you can calculate
the specific heat of the other.

Use the table on the next page to determine the metal in each of the following problems. cp H2O =4.181 J g-1 K-1.

1.)   A 230.11g sample of an unknown metal is heated in boiling water until it achieves thermal equilibrium. When
placed into 150.35g of water, the water’s temperature increases by 10.5K, while the block’s decreases by 74.5K.

a. What is the heat gained by the water?

b. What is the heat lost by the metal?

c. What is the cp of the metal?

d. What is the most likely metal?
HEAT TRANSFER                                            Name: _______________________________ Block: _____
College Prep                                             Partners: ________________________________________

2.)   A 155.25g sample of another metal is heated in boiling water (measured by probe to be 99.8°C). This metal is
placed into a 78.56g sample of water. If the water was initially 21.5°C and ends at 29.3°C,

a. What is the heat gained by the water?

b. What is the heat lost by the metal?

c. What is the cp of the metal?

d. What is the most likely metal?

3.)   Brass is a mixture of copper and zinc. If brass is 61.3% Cu and 38.7% Zn, what would you expect its cp to be?

4.)   **Using the densities, and algebra, prove to me that a brass with a density of 8.25 is the above % of Cu and Zn.**

Sample cp (J g-1 K-1)          M.P. (K)      B.P. (K)      D (kg m-3)
Aluminum         0.897              933.5         2,792           2,7Ō0
Copper       0.385            1,357.8         2,835           8,950
Gold       0.129            1,337.3         3,129          19,300
Iron      0.450               1811         3,134           7,840
Lead       0.129              600.6         2,022          11,340
Silver      0.233            1,234.9         2,435          10,490
Titanium       0.523               1941         3,560           4,506
Tungsten        0.134               3695         5,828          19,250
Water – liquid        4.18               273           373           1,000
Water – ice         2.11               273           373           1,000
Water – steam         2.08               273           373           1,000
Zinc      0.387                693          1180           7,140

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