How is energy transferred and conserved?
Physical Science
PSc.3.1.4 Explain the relationship among work,
power and simple machines both qualitatively and
quantitatively.
PSc.3.1.3 Explain work in terms of the
relationship among the applied force to an
object, the resulting displacement of the
object and the energy transferred to the
object.
PSc.3.1.2 Explain the Law of Conservation of
energy and its applications.
PSc.2.3.1 Compare nuclear reactions including; alpha
decay, beta decay and gamma decay; nuclear fusion
and nuclear fission.
PSc.3.1.1 Explain thermal energy and its
transfer.
PSc.2.3.2 Exemplify the radioactive decay of
unstable nuclei using the concept of half-life.
ENERGY: Conservation & Transfer
How do we quantify energy and track its conservation?
All forms of energy can be measured in the same units; historically a variety of different units were
introduced for different forms and scales of energy. For bookkeeping energy conservation, we need
to know how to convert from one unit system to another, and choose a common one for all forms.
Quantitative application of conservation of energy can predict changes in motion in simple isolated
systems (e.g. falling body in a vacuum, colliding pucks on ice). Mathematical expressions for how
different forms of potential energy depend on relative particle positions, and for kinetic energy, are
needed to do this.
How does energy flow in uncontrolled systems?
Energy tends to dissipate. The stable configuration of any isolated system is the one that distributes
the energy in that system as uniformly as possible between all available forms. Uncontrolled
systems always evolve towards more stable states. This principle is useful for understanding
stability of structures at every scale from the nucleus to the galaxy, and for predicting the way
energy will flow within systems. Unstable objects are any that can fall apart with no added energy.
Eventually they will do so; however, if the energy release in the transition is small, the lifetime for
the transition can be very long (e.g. long-lived radioactive isotopes).
Where do we get energy?
Nuclear fusion processes in the center of the sun provide the energy the earth receives as sunlight
Photosynthesis is a complex chemical process that requires both energy input and a catalyst to
occur. It is the major way the sun’s energy is captured and stored on earth. (see LS1.C) Electric
power generation uses fossil fuels (coal, oil and natural gas), nuclear fission, or renewable resources
(solar, wind, tidal, geothermal and hydropower). Transportation today chiefly uses fossil fuels but
electric and alternate fuel (hydrogen, biofuels) vehicles are a growing sector. All forms of electrical
generation and transportation fuels have associated economic, human, and environmental costs and
risks, both short and long term. Technological developments and regulatory decisions can change
the balance of these factors. (link to ESS3.C)
What is energy efficiency?
While energy cannot be destroyed, it can be converted to less useful forms, such as noise and
thermal energy lost to the surrounding environment. In designing any machine or any system for
energy storage and distribution, maximized efficiency means maximized desired impact per input
fuel. Efficiency is a major element to optimize because it reduces costs, waste materials and other
environmental impacts.
What is the relationship between energy interchanges and force fields?
Force fields contain energy and can transmit energy across space from one object to another. When
two objects interacting through a force field change relative position the energy in the force fields
and the motion of the objects can be changed.
Forces between two interacting objects are always in a direction such that motion in that direction
would reduce the energy in the force field between them, however prior motion and other forces
affect the actual direction of motion.
Light and other forms of electromagnetic waves carry energy across space. Light exerts forces on
matter and changes the energy of the matter as it is absorbed, reflected or transmitted.
How is energy transferred and conserved?
6-8
To Physical Science
8.L.3.3 Explain how the flow of energy within
food webs is interconnected with the cycling
of matter (including water, nitrogen, carbon
dioxide and oxygen). 5A/M5; P8.13
8.L.5.1 Summarize how food provides the
energy and the molecules required for
building materials, growth and survival of all
organisms (to include plants). 5E/M1a
8.L.5.2 Explain the relationship among a healthy
diet, exercise, and the general health of the body
(emphasis on the relationship between respiration
and digestion).5E/M3b.
7.P.2.4 Explain how simple machines such as inclined
planes, pulleys, levers and wheel and axels are used
to create mechanical advantage and increase
efficiency. 4E/M1,2,3
7.P.2.2 Explain how energy can be transformed from
one form to another (specifically potential energy and
kinetic energy) using a model or diagram of a moving
object (roller coaster, pendulum, or cars on ramps as
examples). 4E/M4; P8.8; P8.9; P8.12
7.P.2.1 Explain how kinetic and potential energy
contribute to the mechanical energy of an object.
8C/M1
…from Forces &
Motion
ENERGY: Conservation & Transfer
7.P.2.3 Recognize that energy can be transferred from
one system to another when two objects push or pull
on each other over a distance (work) and electrical
circuits require a complete loop through which an
electrical current can pass.. 4E/M2
6.L.2.1 Summarize how energy derived from the
sun is used by plants to produce sugars
(photosynthesis) and is transferred within food
chains and food webs (terrestrial and aquatic)
from producers to consumers to decomposers.
5E/M1; P8.11; P8.13
6.P.3.3 Explain the suitability of materials for use
in technological design based on a response to
heat (to include conduction, expansion, and
contraction) and electrical energy (conductors
and insulators). 4E/M3
6.P.3.1 Illustrate the transfer of heat energy from
warmer objects to cooler ones using examples of
conduction, radiation and convection and the
effects that may result. 4E/M2,M3; P8.10
6.P.3.2 Explain the effects of electromagnetic
waves on various materials to include absorption,
scattering, and change in temperature. 4E/M6
What is energy? (when viewed at the atomic scale)
Grades 6 – 8
Motion energy is properly called kinetic energy; it is proportional to the mass of the moving object and grows with the square of
its speed. Thermal energy (the term heat as it is commonly used) includes two quite separate forms of energy; these are thermal
motion (motion of atoms or molecules within a substance) and radiation (infrared and light). When light and other forms of
radiation (infrared, ultraviolet) are absorbed by matter their energy generally appears as thermal motion in the matter. In
photovoltaic materials it can appear as electrical energy. Hot objects emit radiation. If they get hot enough we see them glow red
and eventually white and then blue. Temperature is a measure of the average thermal motion in a substance but it is not a
measure of quantity of energy. Different amounts of the same substance at the same temperature contain different amounts of
thermal energy. Gravitational potential energy is the energy stored in the interaction of two massive objects, relative to some
reference situation. Energy stored by deformation of an object (e.g. a stretched or compressed spring) is called elastic potential
energy. The terms mechanical energy and chemical energy are not well defined. Mechanical energy generally refers to some
combination of motion and potential energy in an operating machine. The term chemical energy generally is used to mean the
energy that can be produced by burning fuel or food, or more generally energy released in chemical processes. 7.P.2.1,7.P.2.2,
8.L.5.1, 8.L.5.2, 8.L.5.3
P8.8: Objects and substances in motion have kinetic energy. For example, a moving baseball can break a window; water flowing
down a stream moves pebbles and floating objects along with it.
P8.9: Three forms of potential energy are gravitational, elastic, and chemical. Gravitational potential energy changes in a system
as the relative positions of objects are changed. Objects can have elastic potential energy due to their compression, or chemical
potential energy due to the nature and arrangement of the atoms.
What processes produce the energy we use? What process makes things slow down and stop (lose energy)?
Burning fuel and cellular digestion both are chemical transformations. In these processes carbohydrates react with oxygen to
produce thermal energy, carbon dioxide and other waste materials. Energy cannot be made or destroyed. When we talk about
processes that produce it, we mean a process to store it in concentrated form or produce electrical energy, or chemical reactions
such as burning that release energy. Plants use sunlight to drive a chemical reaction that needs energy to occur. In this reaction
carbon dioxide and water combine to form carbohydrates and release oxygen. (no detailed process at this level). Carbohydrates
in food and carbon-based fuels (coal, oil, gas) are all originally produced by this process. Moving objects tend to lose energy due
to friction with air or surfaces. Friction produces thermal motion. This diffuse energy is generally hard to capture for re-use.
Machines are made more efficient by reducing friction on their moving parts. 8.L.5.2
How does energy get from one object to another?
When two objects interact in any way, each applies a force on the other, and these forces can transfer energy between them.
Gravitational interaction between an object and the earth can store energy as the object is raised and release energy as the object
falls. Interactions in matter can store energy in a stretched or compressed spring, which can transfer energy to and from a weight
on the spring as the spring changes length. Magnetic and electric forces between two objects at a distance can transfer energy
between the interacting objects. 7.P.2.3
P8.10: Energy is transferred from place to place. Light energy from the Sun travels through space to Earth (radiation). Thermal
energy travels from a flame through the metal of a cooking pan to the water in the pan (conduction). Air warmed by a fireplace
moves around a room (convection). Waves (including sound and seismic waves, waves on water, and light waves) have energy
and transfer energy when they interact with matter.
P8.11: A tiny fraction of the light energy from the Sun reaches Earth. Light energy from the Sun is Earth’s primary source of
energy, heating Earth surfaces and providing the energy that results in wind, ocean currents, and storms.
P8.12: When energy is transferred from one system to another, the quantity of energy before transfer equals the quantity of
energy after transfer. For example, as an object falls, its potential energy decreases as its speed, and consequently, its kinetic
energy increases. While an object is falling, some of the object’s kinetic energy is transferred to the medium through which it
falls, setting the medium into motion and heating it.
P8.13: Nuclear reactions take place in the Sun. In plants, light from the Sun is transferred to oxygen and carbon compounds,
which, in combination, have chemical potential energy (photosynthesis).
How is energy transferred and conserved?
ENERGY: Conservation & Transfer
Grades 3 – 5
K-5
Crosscutting Ideas
NAEP, 2009
Physical Science
P4.7: Heat (thermal energy), electricity, light, and sound
are forms of energy. (4.P.3.1, 5.P.2.1, 5.P.3.1, 5.P.3.2)
Life Science
Organisms have basic needs. Animals require air, water,
and a source of energy and building material for growth
and repair. Plants also require light. (1.L.1.1, 1.L2.1,
1.L.2.2 4.l.2.1, 4.L.1.2)
Earth and Space Sciences
The Sun warms the land, air, and water and helps plants
grow. (2.E.1.1,)
5.P.2.1 Explain how the sun’s energy impacts the
processes of the water cycle (including, evaporation,
transpiration, condensation, precipitation). (4B/E3)
5.P.3.1 Explain the effects of the transfer of heat
(either by direct contact or at a distance) that occurs
between objects at different temperatures.
(conduction, convection or radiation) 4E/E2b,c
5.P.3.2 Explain how heating and cooling affect some
materials and how this relates to their purpose and
practical applications. 4D/E1
4.P.3.2 Recognize that light travels in a straight line
until it strikes an object or travels from one medium to
another, and that light can be reflected, refracted, and
absorbed. 4F/E3; P4.9;
4.L.2.1 Classify substances as food or nonfood items based on their ability to provide
energy and materials for survival, growth
and repair of the body. 6E/E1a (5E/2)
3.P.3.1 Recognize that energy can be transferred
from one object to another by rubbing them
against each other. (4E/E1)
4.P.3.1 Recognize the basic forms of energy (light,
sound, heat, electrical, and magnetic) as the ability to
cause motion or create change. P4.7; P4.8; P4.10;
P4.11
3.P.3.2 Recognize that energy can be transferred
from a warmer object to a cooler one by contact or
at a distance and the cooler object gets warmer.
(4E/E2)
Why do we call so many different things forms of energy?
Motion is a form of energy. The faster a given object is moving, the more energy it possesses. Energy can
be moved from place to place by moving objects or through sound, light, or electric currents. (Boundary:
At this grade level, no attempt is made to give a precise or complete definition of energy.) Motion of one
object can be transferred to motion of other objects in a collision. When moving objects collide, sound and
heat are produced. Electricity can produce motion, sound, heat or light. Electric current can transport
energy from place to place through wires. Electricity, sound, heat and light are all forms of energy.
For identical objects at rest, the objects at higher heights have more energy than the objects at lower
heights. You can see this because when this energy is converted to motion as the object falls, the higher it
started, the faster it hits the floor. Moving objects, light, and sound carry energy from place to place in an
organized fashion. Energy flows out of hotter regions or objects and into colder ones, cooling the one and
heating up the other. This happens in three quite different ways: by contact of solid to solid, carried by
flow of fluid in liquid and gas, and by radiant heating which you can feel if you put your hand close to a
stove or fire.
NAEP Framework 2009 P4.7: Heat (thermal energy), electricity, light, and sound are forms of energy.§
P4.8: Heat (thermal energy) results when substances burn, when certain kinds of materials rub against each
other, and when electricity flows though wires. Metals are good conductors of heat (thermal energy) and
electricity. Increasing the temperature of any substance requires the addition of energy. P4.9: Light travels
in straight lines. When light strikes substances and objects through which it cannot pass, shadows result.
When light travels obliquely from one substance to another (air and water), it changes direction. P4.10:
Vibrating objects produce sound. The pitch of sound can be varied by changing the rate of vibration.
P4.11: Electricity flowing through an electrical circuit produces magnetic effects in the wires. In an
electrical circuit containing a battery, a bulb, and a bell, energy from the battery is transferred to the bulb
and the bell, which in turn transfer the energy to their surroundings as light, sound, and heat (thermal
energy).
Clarification: Food
Both plants and animals require a source of energy and materials for growth and repair, and both plants
and animals use high-energy compounds as a source of fuel and building material. Plants are distinguished
from animals by the fact that plants have the capability (through photosynthesis) to take energy from light
to form higher energy molecules containing carbon, hydrogen, and oxygen (carbohydrates) from lower
energy molecules. Plants are similar to animals in that, to make other molecules for their growth and
reproduction, they use the energy that is released as carbohydrates react with oxygen. In making these
other molecules, plants use the breakdown products of carbohydrates, along with minerals from the soil
and from fertilizers (known colloquially as “plant foods”), as building blocks. Plants also synthesize
substances (carbohydrates, fats, proteins, vitamins) that are components of foods eaten by animals.
How is energy transferred between objects or systems?(How does energy get from one object to
another?) Energy is present whenever there are moving objects, sound, light, or heat. When objects
collide, energy can be transferred from one object to another, thereby changing their motion. In such
collisions, some energy is typically also transferred to the surrounding air; as a result, the air gets heated
and sound is produced. Light also transfers energy from place to place. For example, energy radiated from
the sun is transferred to Earth by light. When this light is absorbed, it warms Earth’s land, air, and water
and facilitates plant growth. Energy can also be transferred from place to place by electric currents, which
can then be used locally to produce motion, sound, heat, or light. The currents may have been produced to
begin with by transforming the energy of motion into electrical energy (e.g., moving water driving a
spinning turbine which generates electric currents). Magnets are accompanied by magnetic fields that can
exert forces on other magnets and transfer energy from one to the other.
How is energy transferred and conserved?
ENERGY: Conservation & Transfer
K-2
2.E.1.1 Summarize how energy from the sun serves as
a source of light that warms the land, air and water.
4E/P1
`
Grades K – 2
1.L.2.1 Summarize the basic needs of a variety of different
plants (including air, water, nutrients, and light) for energy
and growth. 5C/P2
1.L.2.2 Summarize the basic needs of a variety of different
animals (including air, water, and food) for energy and
growth. 5C/P2
Who needs energy? How do they get it?
Animals need energy to move around
and grow. They get it from food. Plants need energy
to grow. They get it from sunlight.
Machines can convert energy from one form to
another or can help transfer energy to produce
motion, heat, or light.
We need electricity to make heat and light in our
homes, and to run small machines etc. We get it from
power lines or from batteries.
K.E.1.1 Infer that change is something that happens to many things in
the environment based on observations made using one or more of their
senses. 4C/P2
Supporting Objective:
People can keep track of some things, seeing where they come from and
where they go.
Forms of energy
Conservation
Dissipation
(Transfer)
How is energy transferred and conserved?
ENERGY: Conservation & Transfer
References:
National Center for Education Statistics (2009). The Nation's Report Card: Mathematics
2009 (NCES 2010–451). National Center for Education Statistics, Institute of Education
Sciences, U.S. Department of Education, Washington, D.C.
National Research Council. (2012). A Framework for K-12 Science Education: Practices,
Crosscutting Concepts, and Core Ideas. Committee on a Conceptual Framework for New
K-12 Science Education Standards. Board on Science Education, Division of Behavioral
and Social Sciences and Education. Washington, DC: The National Academies Press.