Performance Benchmark P.12.C.5
Students know the relationship between heat and temperature. I/S
Students often view heat and temperature to be synonymous; they are not. This is a major
misconception that will prevent students from fully understanding energy transfer. In
basic terms heat is a transfer of energy from hot to cold objects. On the other hand,
temperature is a quantity that tells how hot or cold something is compared to a standard.
Heat may be defined as energy in transit from a high temperature object to a lower
temperature object. An object does not possess "heat"; the appropriate term for the
microscopic energy in an object is internal energy. The internal energy of an object may
be increased by transferring energy from a higher temperature (hotter) object, this is
commonly called heating. However, the object can absorb heat and undergo no change in
temperature. A change in temperature is designated by the type of energy storage (i.e.,
potential or kinetic). See the concept map below for examples of heat transfer.
Figure 1. Concept map 1 shows examples of heat transfer. (from http://hyperphysics.phyastr.gsu.edu/hbase/thermo/heatranex.html#c1)
In an ideal gas, temperature is a measure of the average translational (picture “sliding”
molecules) kinetic energy associated with the disordered microscopic motion of atoms
and molecules. In solids and liquids, molecules are more constrained, and in addition to
their kinetic energy, they have a significant component of potential energy. Therefore, the
calculation of temperature is more complex. In general terms, temperature measures how
“hot” or how “cold” something is compared to a standard. Nearly all matter expands
when its temperature increases and contracts when its temperature decreases, as the
matter approaches thermal equilibrium.
The common thermometer works according to thermal equilibrium. The thermometer
measures temperature by showing the expansion and contraction of a liquid, most often
mercury or alcohol, in a glass tube with gradations. The faster the molecules within the
material are moving, the more they “bump” into the liquid in the thermometer. This is a
transfer of kinetic energy from the material to the liquid within the thermometer. The
liquid in the thermometer continues to expand or contract until it reaches thermal
equilibrium with the material in which it is measuring. Thermometers can not
measurement the total amount of internal energy in an object, only the average
translational kinetic energy.
To learn more about thermal equilibrium go to
http://www.grc.nasa.gov/WWW/K-12/airplane/thermo0.html
The Celsius scale is the most commonly used temperature scale. The Celsius scale is
based on water at standard atmospheric pressure assigning a value of 0o for freezing
water and 100o for boiling water. The gradations between freezing and boiling water is
divided into 100 equal parts. Gradations on the Celsius scale and the Kelvin (absolute
temperature) scale are equivalent. On the Kelvin scale the number 0 is assigned to the
lowest possible temperature, absolute zero. At absolute zero a substance has no kinetic
energy to give up.
To learn more about temperature and scales go to
http://www.eo.ucar.edu/skymath/tmp2.html#Dev.
Figure 2. A Florentine
thermoscope, one of the first
thermometers. (from
http://www.eo.ucar.edu/skymath/tm
p2.html#Dev)
Heat and temperature are related in terms of internal energy. The internal energy of a
substance is a measure of the amount of kinetic and potential energy. Their relationship
is governed by the laws of thermodynamics.
The First Law of Thermodynamics is explained through energy transfer (both heat and
mechanical energy as work). The law states that the change in the internal energy of a
system is equal to the heat added to the system minus the work done by the system. This
is written as:
Figure 3. The equation for the First Law of Thermodynamics. (from
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/firlaw.html#c1)
The change in the internal energy (ΔU) of a system is a change in the potential and
kinetic energy of the system. The relationship between heat (energy transfer) and
temperature is found in the type of energy storage, either potential (no gain in
temperature) or kinetic (gain in temperature).
To learn more about internal energy go to
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/inteng.html#c2.
The Second Law of Thermodynamics designates that, in the absence of an external effort,
heat flows only from higher to lower temperature, and that some energy is lost to the
environment. The amount of heat that is lost to the environment depends greatly upon
the efficiency of the system. This heat loss adds to the disorder of a system, this disorder
is called entropy.
To learn more about the Second Law of Thermodynamics go to
http://www.grc.nasa.gov/WWW/K-12/airplane/thermo1.html
The SI unit for heat is the joule (J). The most common form of quantifying heat is with
the measurement of a calorie. The calorie is the amount of heat needed to raise 1g of
water by 1oC. Food Calories, 1000 calories, are also a common quantifier of energy. The
relationship between calories and joules is that 1 calorie is equal to 4.187 J. The energy
value in food is determined by burning the food and measuring the quantity of internal
energy that is released as heat.
Heat can be measured as sensible heat and latent heat. Sensible heat can be calculated
through the equation Q = mcΔT, where the mass (kg) of the material multiplied by the
specific heat of the material multiplied by the change in temperature of the material.
Specific heat is the measure of the amount of energy required to raise the temperature of
a unit of mass of a substance by one degree. This is a direct relationship between
temperature change and heat.
To learn more about specific heat go to
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html#c1
Latent heat refers to the amount of energy that must be absorbed or emitted in order for a
material to complete a phase change. The equation for latent heat is Qf = mHf and Qv =
mHv, where the mass (kg) of the material multiplied by the latent heat of fusion (J/kg) [or
vaporization (J/kg)] is equal to the amount of energy required for the phase change. The
temperature of a material does not change during a phase change even though the
material is being heated. If energy is added then the internal energy of the system is
increasing as heating occurs, but the energy is stored as potential energy. This is why it
is undetectable with a thermometer.
To learn more about latent heat and phase change go to
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase.html#c1.
Figure 4. The energy involved in the heating of water. Note that the temperature does not
change while heating occurs throughout each phase change. (from http://hyperphysics.phyastr.gsu.edu/hbase/thermo/phase.html#c1.)
Heat transfer occurs because there is a temperature difference between two objects and
there are three basic mechanisms in which heat is transferred between objects of different
temperature: (1) conduction, (2) convection, and (3) radiation.

Conduction occurs within materials and between materials that are in direct
contact. Materials that conduct heat well are known as conductors. Materials that
are poor conductors are referred to as insulators.
To learn more about conduction go to
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatra.html#c2.

Convection occurs by currents through a fluid. Fluids may be defined as a liquid
or gas. Convection cells are caused by heating and changes in density. As a
heated medium expands it becomes less dense than the surrounding material, this
is what causes it to rise.
To learn more about convection go to
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatra.html#c3.

Radiation is the transfer of energy (including heat) through electromagnetic
waves. This form of heat does not require a medium in which to travel. Energy is
carried away from the emitting object.
To learn more about radiation go to
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c2.
Performance Benchmark P.12.C.5
Students know the relationship between heat and temperature. I/S
Common misconceptions associate with this benchmark
1. Students incorrectly believe that “heat is an object or something other than
energy.”
Students often want to view heat as a property of a material. This is not a new
misconception as the word calorie stems from caloric, which was once thought to be an
invisible heat fluid. Today we know that heat is one of three ways in which energy is
transferred.
To learn more about heat as a form of energy transfer go to
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heat.html#c1.
2. Students incorrectly think that when objects are heated the particles expand and
when objects are cooled the particles contract.
Students need to realize that thermal expansion and contraction doesn’t occur within the
molecule. The atoms do not expand and contract. Expansion is due to the increase in
vibrational, rotational, and translational kinetic energy gain. If you were to drop a box of
golf balls off the roof of a second story building the balls, upon hitting the ground, would
bounce and scatter. This is similar to thermal expansion in that the golf balls, like the
material undergoing thermal expansion, do not grow in size as they increase the amount
of space between other balls.
To learn more about thermal expansion go to
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thexp.html#c1
To learn how to use thermal expansion too your advantage, go to
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/jarlid.html#c1.
3. Students may incorrectly think that temperature depends on the material (i.e.,
metal is colder than fabric or that blankets and coats are warm objects because
clothes keep you warm.
The above misconception stems from the thought that energy is a property of an object
and the lack of understanding about how energy is transferred. A tile floor will “feel”
colder. This is true, but not because tile is an inherently “cold” material. This is true
because tile is a good conductor of heat compared to carpet. While students walk on a
tile floor energy transfers, according to the Second Law of Thermodynamics, from their
feet to the floor. This also occurs with a carpeted floor just not as quickly because carpet
has trapped air which is an insulator.
To learn more about thermal conductors and insulators go to
http://hypertextbook.com/physics/thermal/conduction/..
3. Students incorrectly believe that temperatures are additive.
“If you mix 40 degree water with 40 degree water you get 80o water, or more than 40o
water.” This is a common misconception that occurs because students lack a complete
understanding of the concept of internal energy and work. If you were to mixing two
sources of water at the same temperature then the resulting temperature will be the same.
This is an offshoot of the Zeroth Law of Thermodynamics, which concerns thermal
equilibrium. Also, if the amounts of water are different then their resulting temperature
will be a function of their masses and original temperatures.
To learn more about the Zeroth Law of Thermodynamics, go to
http://www.grc.nasa.gov/WWW/K-12/airplane/thermo0.html
Performance Benchmark P.12.C.5
Students know the relationship between heat and temperature. I/S
Sample Test Questions
1. Two blocks of metal are placed into an insulated container and there is a net flow
of heat between the blocks. Which of the following statements must be true?
a. The blocks started with the same temperature.
b. The blocks have a different specific heat.
c. The blocks started with a different temperature.
d. The blocks have the same melting point.
2. The graph below represents the temperature of 6.0 kg of water as a function of
heat added to the substance.
Figure 5. A plot of how water temperature changes when heat
is added (from
http://itl.chem.ufl.edu/2045_s00/lectures/lec_f.html).
During which two intervals, shown on the graph (Figure 5 above), is only the
average potential energy of the molecules of the material increasing?
a. AB and CD
b. BC and DE
c. CD and DE
d. AB and EF
3. During which two intervals, shown on the graph (Figure 5 above), is the average
translational kinetic energy of the molecules of the material increasing?
a. AB and CD
b. CD and DE
c. BC and DE
d. AB and DE
4. The sum of the kinetic and potential energies of an object’s molecules is called
the object’s
a. Temperature
b. Heat of fusion
c. Specific heat
d. Internal energy
5. If you mix 50 ml of water at 100oC with 50 ml of water at 0oC what will be the
resulting temperature of the 100ml of water?
a. 100oC
b. 75oC
c. 50oC
d. 25oC
6. Why does a ceramic tile floor feel colder than a carpeted floor when they are in
the same room?
a. A ceramic tile floor has less heat than a carpeted floor.
b. A carpeted floor feels warmer because it has a higher temperature.
c. A ceramic tile floor is a better thermal conductor than a carpeted floor.
d. A carpeted floor transfers energy faster than a ceramic tile floor.
7. The three basic mechanisms for heat transfer are conduction, convection and
radiation. Which of these three types require the direct contact of material?
a. convection and radiation
b. conduction only
c. radiation and conduction
d. radiation only
Performance Benchmark P.12.C.5
Students know the relationship between heat and temperature. I/S
Answers to Sample Test Questions
1.
2.
3.
4.
5.
6.
7.
(c)
(b)
(a)
(d)
(c)
(c)
(b)
Performance Benchmark P.12.C.5
Students know the relationship between heat and temperature. I/S
Intervention Strategies and Resources
The following list of intervention strategies and resources will facilitate student
understanding of this benchmark.
1. ThePhysicsFront.org Lessons, Activities, and Resources
The National Science Foundation, American Association of Physics Teachers,
and National Science Digital Library has created ThePhysicsFront.org , a Web
site for Physics Educators that has a collection of high-quality, ready to use lesson
plans. The lesson plans are complete with labs, activities and further resources.
Lesson plans and activities for heat and temperature can be found at
http://www.thephysicsfront.org/search/search.cfm
2. HyperPhysics Web Site
Georgia State University’s Hyperphysics (http://hyperphysics.phyastr.gsu.edu/hbase/hph.html) Web site is one of the most complete physics
content resources available. The site is a lattice of concept maps with hyperlinks
to each topic. Most topics have an outline of content with links to further content,
applets for practice problems, and further resources. Students can click on
concepts within the concept maps to view more information, and see the
interconnections throughout basic physics concepts
The section that deals with heat and temperature is
http://hyperphysics.phy-astr.gsu.edu/hbase/heacon.html#heacon
3. Hands-On-Physics Problem Solving Unit
The Concord Consortium’s Hands-On-Physics Web site offers a unit on heat and
temperature. The unit presents several projects which will help your students
understand heat. Students start by learning how to measure temperature. As the
unit unfolds, students are introduced to the major concepts of heat and
temperature through a series of interesting projects.
For information about Hands-On-Physics go to
http://hop.concord.org/h1/info/h1i.html
4. Interactive Heat Experiment
Davidson University offers an exercise that explores the changes that occur to a
substance during heating. The site is linked to an applet that allows students to
manipulate variables within a phase change experiment. At the outset of the
experiment, a cylinder is equipped with a movable barrier and contains 0.200
mole of a pure solid. The barrier is exposed to the atmosphere and thus the
material in the cylinder experiences a constant pressure at all times during the
experiment. During the experiment students can view temperature time graph that
plots a phase change graph. Questions follow the graph to check for
understanding.
To learn more go to
http://www.chm.davidson.edu/ChemistryApplets/PhaseChanges/HeatingCurve.ht
ml.