Content Benchmark P.8.C.3
Students know physical, chemical, and nuclear changes involve a transfer of energy. E/S
Energy Transfer
Matter undergoes physical, chemical and nuclear changes. What causes these changes to occur?
Energy is the ability to do work and therefore the ability to make changes in matter. When a
physical change occurs, work has been done on the matter to change the texture, shape, size,
color, odor, volume, mass, weight, density or any other physical property of the matter. This
energy can be transferred via different mechanism, such as heat, light, sound, mechanical
motion, etc. Energy is transferred to the matter from some other source.
What is Energy?
Energy is involved in change and is transferred throughout systems. Energy is commonly defined
as the ability to do work. People have learned how to change energy from one form to another so
that we can do work more easily and live more comfortably.
Energy is transferred in many ways: heat, light, electricity, mechanical motion, sound, and
nuclear and chemical transformations.
This Physics Classroom website gives a good summary of the basic concepts and terminology
related to energy and is found at http://www.newspapersites.net/Guide/the-physics-classroomglenbroo.asp. Once on the site, click on “Work, Energy, and Power” in the left-hand menu bar.
The U.S. Department of Energy has a nicely organized website that charts different energy
transformations, located at http://www.eia.doe.gov/kids/energyfacts/science/formsofenergy.html.
In physical changes, as well as chemical and nuclear reactions, energy is transferred into or out
of a system. Heat, light, mechanical motion, electricity or other energy transfer mechanism might
all be involved in such transfers. However, the Law of Conservation of Energy applies to all
physical, chemical, and nuclear changes, regardless of the mechanisms,
To learn more about the Conservation of Energy, please see the TIPS benchmark P.8.C.4.
Units of Energy
The primary SI unit for energy is the Joule. It is equal to the amount of work required when 1N
of force is applied for a distance of one meter (Nm). An expenditure of one Joule per second is a
Watt. Watts are the SI units for Power. A calorie is equal to the energy needed to heat one gram
of water one degree centigrade. One calorie is equal to 4.184 Joules. The calories on food
packaging are actually kilocalories. A BTU (British Thermal Unit) is the amount of heat
necessary to raise one pound of water by 1 degree Fahrenheit (F).
To learn more about energy and its conversions please see
http://www.aps.org/policy/reports/popa-reports/energy/units.cfm
Energy in Physical Changes
Physical changes occur when objects undergoes a change that does not change their chemical
nature. A physical change involves a change in physical properties. Physical properties can be
observed without changing the type of matter. Examples of physical properties include: texture,
shape, size, color, odor, volume, mass, weight, and density.
When a substance undergoes a physical change, an energy transfer occurs. Work is being done
on the object to cause it to change. For example, when water is heated or cooled it undergoes a
physical change. Kinetic energy of the particles within an object (sometimes called thermal
energy) is either added or taken out of the water to cause it to change phase. As thermal energy is
continuously added to the water, kinetic energy of the water molecules increases. Because
temperature is the measurement of the average kinetic energy of the molecules, the temperature
of the water also increases, as show in Figure 1.
Figure 1. An example of a heating curve showing the change in temperature over a
period of time as energy is continuously added.
(From http://www.humboldt.edu/~rap1/Sci331/Sci331_FinalSG_b.html)
At two points in this Figure 1, the heating curve plateaus. When these plateaus occur, the added
energy does not contribute to a change in temperature. Instead it causes a change in phase. This
occurs at 0ºC when the water changes phase from solid to liquid or conversely, liquid to solid. It
occurs again at 100ºC when it changes phase from liquid to gas or conversely, from gas to liquid.
More information about phase changes can be found in the TIPS benchmark P.8.A.1 discussion.
To learn more about physical changes, go to
http://www.schools.utah.gov/curr/science/sciber00/8th/matter/sciber/change.htm
Energy in Chemical Changes
In a chemical change, a substance undergoes a reaction in which the new substance (product) has
different properties than the original substance (reactant(s)). All chemical reactions are
accompanied by energy transformations. Some reactions release energy to their surroundings,
usually in the form of heat transfer, and are called exothermic. On the other hand, some
reactions have heat transferred from their surrounds to proceed. These reactions are called
endothermic.
Good examples of exothermic and endothermic reactions can be seen in commercial instant hot
and cold packs. Commercial packs usually consist of two compounds that when combined will
release energy to its surroundings or absorb energy from its surroundings. Some hot packs
consist of sodium acetate and air. When the sodium acetate is allowed to mix with the air,
crystallization occurs and thermal energy within the pack increases, resulting in an increased
temperature and the pack getting hotter. In a commercial instant cold pack, urea and ammonium
chloride are held in separate containers within a plastic bag. When the bag is bent and the inside
containers are broken, the two compounds mix together and begin to react. Because the reaction
is endothermic, heat is transferred from the surrounding environment and the bag gets cold.
To learn more about chemical changes, go to
http://www.ric.edu/faculty/ptiskus/chemical/
Energy in Nuclear Changes
A nuclear change involves changes in nuclear structure, such as fission (splitting) of a nucleus,
or fusion (combining) of neutrons and protons to form heavier atoms.
In nuclear fission reactions, an atom's nucleus splits into smaller parts, releasing a large amount
of energy in the process. Nuclear fission is a process by which an atom’ nucleus is split by a
neutron. This results in the formation of two or more new atoms that are smaller than the
original atom. Most commonly this is done by "firing" a neutron at the nucleus of an atom. The
energy of the neutron "bullet" causes the target element to split into two (or more) elements that
are lighter than the parent atom.
The Fission Reaction of Uranium-235
Figure 2. This is an example of fission of U235 atom. As the atom splits it releases energy and
transforms into new atomic structures (Sr90, Xe143 and 3 neutrons).
(Please note that Flash is required to see this figure animated)
(From http://www.visionlearning.com/library/module_viewer.php?mid=59)
During the fission of U-235, three neutrons are released in addition to the two progeny atoms.
If these released neutrons collide with nearby U-235 nuclei, they can stimulate the fission of
these atoms and start a self-sustaining nuclear chain reaction. This chain reaction is the basis of
nuclear power. As uranium atoms continue to split, a significant amount of energy is released
from the reaction. The heat transferred during this reaction is typically used to increase water
temperature, creating steam, which can then be used to generate electrical energy.
Nuclear fusion reactions are reactions in which two or more elements "fuse" together to form
one larger element, releasing energy in the process. A good example is the fusion of two
"heavy" isotopes of hydrogen (deuterium: H-2 and tritium: H-3) into the element helium.
Nuclear Fusion of Two Hydrogen
Isotopes
Figure 3. This is an example of nuclear fusion in a tokamak reastor. Deuterium and Tritium fuse.
As they fuse they release energy and become He4.
(Please note that Flash is required to see this figure animated)
(From http://www.visionlearning.com/library/module_viewer.php?mid=59)
Fusion reactions release tremendous amounts of energy and are commonly referred to as
thermonuclear reactions. Although many people think of the Sun as a large fireball, the Sun (and
in fact all stars) are actually enormous fusion reactors. Stars are primarily gigantic balls of
hydrogen gas under tremendous pressure due to gravitational forces. Hydrogen molecules are
fused into helium and heavier elements inside of stars, releasing energy that is transferred as
light. The tremendous mass of stars provides a large amount of gravitational potential energy
which is needed to achieve nuclear fusion. The positively charged nuclei repel each other, and
therefore, the nuclei strongly resist being forced together. When the interior of the star achieves
tremendous temperatures (greater than 1 million Kelvin), they hydrogen nuclei can overcome
this repulsion and get close enough for the attractive nuclear force to take over.
To learn more about nuclear changes, go to
http://www.visionlearning.com/library/module_viewer.php?mid=59
Content Benchmark P.8.C.3
Students know physical, chemical, and nuclear changes involve a transfer of energy. E/S
Common misconceptions associated with this benchmark
1. Students incorrectly believe that energy is truly lost in many energy transformations.
The Law of Conservation of Energy states that energy can be neither created nor destroyed. It
can only be transferred (transformed). The total amount of energy in the universe remains
constant. Students may believe that energy is used up the way that a battery is used up. Students
cannot see the energy; therefore, they cannot see where it is being transferred to or how it is
being transformed. The battery’s energy is transformed into other forms such as sound, heat and
light, which do not disappear, but may not be noticeable to the student, especially if the battery is
disconnected from a circuit. Ask students where the energy is going or how it is transformed.
Also, having a diagram of energy flow might be useful in identifying student misconceptions.
The following website provides information about conservation of energy. In addition to
explanations and mathematical formulas, it has simulations that demonstrate what happens to the
energy as it is transformed.
http://www.fi.edu/guide/hughes/energyconservation.html.
2. Students incorrectly believe that energy is a “thing”, an object or something that is
tangible.
Students view energy as a fuel or something that is stored, ready to use, and gets used up. The
intent at this level is for students to improve their understanding of energy by experiencing many
kinds of energy transfer. In such experiences, students may begin to understand that energy is not
a substance to be used up. Fuel (such as oil or food) is a resouce that allows energy to be
transformed when its chemical make up is changed. The chemical bonds contain potential energy
that may be transferred to kinetic energy during combustion, which in turn, can be transferred
(via work) to kinetic energy that allows pistons to move in an engine. The students only see the
resource and the end result of work being done. Students must walk through the process of
transformation to understand that the resource is not energy.
This following article offers a good insight into the student misconception that energy is a thing.
It also offers a true/false quiz to help identify student misconceptions about energy.
http://www.powernaturally.org/programs/pdfs_docs/1_energy_misconceptions.doc.
3. Students are confused about the difference between conservation of energy and energy
conservation.
Students often ask, “If energy is conserved, why are we running out of it?” Students have
difficulty separating the idea that energy is transformed or transferred into a form that is no
longer directly useful to power devices. Students also have difficulty with the concept that even
though energy is conserved, it is no longer in a useful form. Increasingly, as we transform the
energy from one type to another it becomes less and less useful. This concept is directly related
to the Second Law of Thermodynamics.
For more information the Second Law of Thermodynamics go to
http://www.entropylaw.com/entropy2ndlaw.html
4. Students often think that nuclear reactions are the only way to get energy from particles.
A study was conducted at Kansas State University to find out what students’ misconceptions are
about the atom. The majority of students correctly identified nuclear reactions, but most did not
mention any other relationship between atoms and energy such as electromagnetic radiation,
electricity, or chemical reactions.
This following document addresses student misconceptions about nuclear energy. It is a lesson
plan that asks the student to describe their ideas about nuclear energy, gives the teacher internet
resources for addressing those concepts, and offers a test for pre and post content ideas.
To download the misconception information and lesson, go to
http://www.paec.org/progressenergygrant/nuclear_energy_transformed.pdf.
Content Benchmark P.8.C.3
Students know physical, chemical, and nuclear changes involve a transfer of energy. E/S
Sample Test Questions
Questions and answers will be sent in a separate document
Content Benchmark P.8.C.3
Students know physical, chemical, and nuclear changes involve a transfer of energy. E/S
Answers to Sample Test Questions
Questions and answers will be sent in a separate document
Content Benchmark P.8.C.3
Students know physical, chemical, and nuclear changes involve a transfer of energy. E/S
Intervention Strategies and Resources
The following is a list of intervention strategies and resources that will facilitate student
understanding of this benchmark.
1. School Power….Naturally
Developed by the New York State Energy Research and Development authority, this website
offers a variety of energy lesson plans. The lesson plans are complete with labs and activities and
further resources. Lesson plans include: energy misconceptions quiz, fossil fuel dependence, the
future of solar power, energy conversion games, energy resources, energy solutions, mechanical
advantage, the absorption of solar energy, how photo cells work, electrical power, the refining of
crude oil, nuclear fusion from the sun, the sun and the water cycle, pH, effect of acid rain, the
carbon cycle and the greenhouse effect.
To access these activities, go to
http://www.powernaturally.org/Programs/SchoolPowerNaturally/InTheClassroom/level2.asp?i=9
2. Heat Transfer Lab: Ice Cream!
Developed by the University of Virginia Physics Department, this lab is an interesting way for
students to look at energy transfers and its effect on matter. The website gives you a list of
ingredients and procedures, typical questions relative to energy transfer, suggestions for
inclusion, and an assessment.
This lab can be viewed at
http://galileo.phys.virginia.edu/education/outreach/8thgradesol/TastyPhaseChangeFrm.htm.
3. Solar Cookout
Developed by the NEED Project, this is an excellent design for an inexpensive solar oven that
can be used to teach students about solar energy transfer from the sun to the food. This design
works well for cooking hot dogs or marshmallows. It incorporates the foil lined ‘Pringles’ cans.
Time to cook is around 45 minutes on a sunny afternoon without additional insulation.
This activity can be downloaded at
http://www.eia.doe.gov/kids/classactivities/SolarCookingIntermediateActivity.pdf.
4. Energy Quest Room
Developed by the California Energy Commission, this website includes projects, experiments,
and descriptions of many types of energy. This website is highly interactive! It has short movies
on energy as well as games and other interactive media. “The Story of Energy” includes
information on the generation and transmission of electricity as well as biomass, geothermal,
hydro, nuclear, ocean, solar and hydrogen energy sources. The website encourages conservation
and gives students information on energy conservation in their home and community.
Go to this website by clicking on http://www.energyquest.ca.gov/.