2020 Physics: Energy and Thermodynamics

PH.PS1.8 Develop models to illustrate the changes in the composition of the nucleus of the atom and the energy released during the processes of fission, fusion, and radioactive decay.

PH.PS3.1 Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known.

PH.PS3.2 Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as either motions of particles or energy stored in fields.

PH.PS3.3 Design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy.*

PH.PS3.4 Plan and conduct an investigation to provide evidence that the transfer of thermal energy between components in a closed system results in a more uniform energy distribution among the components in the system (second law of thermodynamics).

In a Nutshell

Students use pictures or diagrams to illustrate changes in the numbers of protons and neutrons of an atom and the scale of energy released during the processes of fission, fusion, and radioactive decay. Radioactive decay alters the nucleus of an atom, creating a different atom by releasing particles, energy, and radiation from the nucleus. Fission and fusion also alter the nucleus of unstable atoms by either combining smaller atoms to create a larger, more stable atom, or breaking down larger atoms into smaller atoms. Both processes involve either the release or absorption of energy. Energy cannot be created or destroyed. It can be transferred within and/or into and out of a system. Energy is understood as a quantitative property of a system that depends on the motion and interaction of matter. The total change of energy in any system is equal to the total energy transferred into and out of the system. As energy is conserved, students can develop computational models to calculate changes in energy for components of a system if they know how much energy is going into or out of the system. A system with components of differing energy levels will transfer energy between components until there is a more uniform energy distribution among the components of the system. On a macroscopic scale, energy is exhibited  as motion, sound, light, and thermal energy. Using student-developed models, these different forms of energy can be represented at the microscopic scale as a combination of energy associated with the motion of the particles and the relative position of the particles (energy stored in fields). By knowing how energy flows in, out, and through systems, students can design, build, evaluate, and refine devices that use and/or transform energy to perform specific functions.

Student Actions

Teacher Actions 

• Develop a qualitative model to explain how radioactive decay alters the nucleus of the atom while conserving the total number of protons and neutrons.

• Use a qualitative model to illustrate the scale of energy that is released or absorbed during fission, fusion, and radioactive decay.

• Analyze and interpret qualitative and quantitative data to identify systems in which different forms of energy are transferred and their total is conserved. 

• Develop and use a mathematical model to identify the energy inputs and/or outputs in a system and calculate unknown values from known values. 

• Use mathematical and computational thinking to accurately explain and describe that energy is a property of a system that depends on the motion and interaction of the parts of a system.

• Use mathematical models to describe an interaction and how energy is transferred within the described system. 

• Use a model to construct an explanation that the total amount of energy contained within a system will limit what can occur within that system.

• Develop and use models to show that the energy is conserved in a closed system on both the macroscopic scale (such as motion, sound, light, thermal energy, potential energy or energy) and the microscopic scale (such as motions/kinetic energy of particles, the relative positions of particles in fields/potential energy, and energy in fields).

•  Develop and use models to illustrate that energy at the macroscopic scale is a combination of energy associated with the motions of particles/objects and energy associated with the relative positions of particles/objects (stored in fields).

• Design, build, evaluate, and refine a device that works within given quantitative and qualitative constraints to convert one form of energy into another form of energy. 

• Analyze data from investigations to provide evidence that, in a closed system, the transfer of thermal energy from a hot object is equal to the thermal energy gained by the cold object.

• Plan and conduct an investigation to provide evidence that the transfer of thermal energy from a hot object to a cold in a closed system, results in a more uniform energy distribution among the components in the system. 

• Support students in developing qualitative models that illustrate the changes in the nucleus of an atom and the scale of energy released during fission, fusion, and radioactive decay.

• Guide students in developing a computational model by identifying and describing the components of the model, including system boundaries, initial and final energies, and energy flows in or out of the system.

• Provide tasks that require students to develop and use mathematical models for calculating the change in energy of one component in a system when the change of energy of the other components are known.

• Assist students in using computational thinking to accurately explain conservation of energy and energy transformation within the described system. 

• Provide tasks that require students to use data as evidence to support the claim that the total amount of energy contained within a system will limit what can occur within that system.

• Provide tasks for students to develop and use models to illustrate how energy at the macroscopic scale (i.e., motion, sound, light, thermal) is a combination of energy associated with the motion of particles and the relative position of the particles.

• Pose purposeful questions that assist students in designing, building, evaluating and refining a device that works within given quantitative and qualitative constraints to convert one form of energy into another form of energy. 

• Provide materials students can use to plan and conduct investigations that result in data that supports the claim that the transfer of thermal energy between objects in a closed system results in a more uniform energy distribution among the components in the system.  

Key Concepts 

Misconceptions 

Nuclear Processes

• Nuclear processes, including fusion, fission, and radioactive decays of unstable nuclei, involve release or absorption of energy. 

• The total number of neutrons plus protons does not change in any nuclear process.

Definitions of Energy

• Energy is a quantitative property of a system that depends on the motion and interactions of matter and radiation within that system. 

• That there is a single quantity called energy is due to the fact that a system’s total energy is conserved, even as, within the system, energy is continually transferred from one object to another and between its various possible forms.

• At the macroscopic scale, energy manifests itself in multiple ways, such as in motion, sound, light, and thermal energy.

• These relationships are better understood at the microscopic scale, at which all of the different manifestations of energy can be modeled as a combination of energy associated with the motion of particles and energy associated with the configuration (relative position of the particles). In some cases the relative position energy can be thought of as stored in fields (which mediate interactions between particles). This last concept includes radiation, a phenomenon in which energy stored in fields moves across space.

Conservation of Energy and Energy Transfer

• Conservation of energy means that the total change of energy in any system is always equal to the total energy transferred into or out of the system.

• Energy cannot be created or destroyed, but it can be transported from one place to another and transferred between systems.

• Mathematical expressions, which quantify how the stored energy in a system depends on its configuration (e.g. relative positions of charged particles, compression of a spring) and how kinetic energy depends on mass and speed, allow the concept of conservation of energy to be used to predict and describe system behavior.

• The availability of energy limits what can occur in any system.

• Uncontrolled systems always evolve toward more stable states—that is, toward more uniform energy distribution (e.g., water flows downhill, objects hotter than their surrounding environment cool down).

Defining and Delimiting an Engineering Problem

• Criteria and constraints also include satisfying any requirements set by society, such as taking issues of risk mitigation into account, and they should be quantified to the extent possible and stated in such a way that one can tell if a given design meets them.

Interdependence of Science, Engineering and Technology

• Modern civilization depends on major technological systems.  Engineers continuously modify these technological systems by applying scientific knowledge and engineering design practices to increase benefits while decreasing costs and risks. 

• When an atom undergoes radioactive decay, the identity of the atom remains the same.

• The conservation of atoms and mass is not the same as the conservation of nucleons.

• There is no relationship between matter and energy.

• An object at rest has no energy.

• Gravitational potential energy depends only on the height of an object.

• Doubling the speed of a moving object doubles the kinetic energy.

• ­Motion energy is not transformed into thermal energy, especially when there is no noticeable temperature increase.

• Mathematical models are only used to calculate values, not to describe relationships. 

• Energy is a thing, an object or something that is tangible.

• The only type of potential energy is gravitational.

• The gravitational potential energy of an object depends upon the path the object takes to get to the distance above the reference points.

• Thermal energy is not related to the kinetic energy of the molecules that make up an object.

• ­Energy can be lost, created, or destroyed.

• Energy is truly lost in many energy transformations.

• One form of energy cannot be transformed into another form of energy (e.g. chemical energy cannot be converted to kinetic energy).

• Motion energy is not transformed into thermal energy, especially when there is no noticeable temperature increase.

• When two objects at different temperatures are in contact with each other, thermal energy is transferred from the warmer object to the cooler object and “coldness” or ”cold energy” is transferred from the cooler object to the warmer object.

• Energy is lost during thermal energy transfer.

• Thermal energy cannot be measured.

• If energy is conserved, why are we running out of it?

Instructional Resources 

Unit 2: Energy and Thermodynamics