PLC Activity #2
Heat and Temperature
Due: See website for due date
How to get credit for this activity
First, sign-in at the computer and sign-out when the activity is complete. Show your work and
results to a PLC tutor so they can check your work and initial the signoff sheet. Be prepared to
answer questions about the activity or your results.
Part 1: Heat and Temperature
Physlet Problem 19.4
The animation shows a close-up of the bottom-left corner of the square opening in a sheet of
material (position is given in millimeters and time is given in minutes).
The initial temperature is 300 K, which changes (increases or decreases) by 200 K over the
time of the animation (t = 2 minutes). The opening is initially a 20 cm x 20 cm square. Restart.
a. Determine if the temperature is increasing or decreasing.
b. Find the coefficient of linear expansion.
Physlet Problem 19.8
A piece of metal sits in a thermally insulated container of water (position is given in centimeters,
temperature is given in Kelvin, and time is given in arbitrary units). Restart. The dimension of
the water you cannot see (into the computer screen) is 25 cm and the dimension of the metal
you cannot see is 10 cm. The mass of the metal is 2 kg. The graphs show the temperature of
the metal and of the water as a function of time. What is the specific heat capacity of the
metal?
Part 2: Ranking Problems
Question 1
A hot object is dropped into a thermally insulated container of water, and the object and water
are then allowed to come to thermal equilibrium. The experiment if repeated twice, with different
hot objects. All three objects have the same mass and initial temperature and the mass and
initial temperature of the water are the same in the three experiments. For each of the
experiments rank the graphs according to the specific heats of the objects, greatest first.
1-1
Question 2
Three different materials of identical masses are placed, in turn, in a
special freezer that can extract energy from a material at a certain
constant rate. During the cooling process, each material begins in the
liquid state and ends in the solid state; the figure shows graphs of the
temperature T versus time t for the three materials.
(a) For material 1, is the specific heat for the liquid state greater than or less than that for the
solid state? Rank the materials according to (b) their freezing-point temperatures, (c) their
specific heats in the liquid state, (d) their specific heats in the solid state, and (e) their heats of
fusion, all greatest first.
Question 3
A sample A of liquid water and a sample B of ice, of identical mass, are placed in a thermally
insulated container and allowed to come to thermal equilibrium. Figure (a) is a sketch of the
temperature T of the samples versus time t. (a) Is the equilibrium temperature above, below, or
at the freezing point of water? (b) In reaching equilibrium, does this liquid partly freeze, fully
freeze, or undergo no freezing? (c) Does the ice partly melt, fully melt, or undergo no melting?
Question 4
Question 3 continued: Graph b through f are sketches of T verses t, of which one or more are
impossible to produce. (a) Which is impossible and why? (b) In reaching equilibrium, does this
liquid partly freeze, fully freeze, or undergo no freezing? (c) Does the ice partly melt, fully melt,
or undergo no melting?
1-2