Next Generation Science Standards

Performance Expectation

Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative positions of particles (objects).

• Clarification Statement: Examples of phenomena at the macroscopic scale could include the conversion of kinetic energy to thermal energy, the energy stored due to position of an object above the earth, and the energy stored between two electrically-charged plates. Examples of models could include diagrams, drawings, descriptions, and computer simulations.

If you've ever tried to build a fire by rubbing two sticks together, you know that converting kinetic energy into thermal energy isn't easy. Don't worry, students won't need to use their Survivor skills for this performance expectation.

They will need to use their modeling skills, however. Their job is to develop and use a model that shows how the energy we see at a macroscopic level is a result of a bunch of particle interactions and motion we can't see at a microscopic level. They won't have to worry about being voted off the island, because they'll be energy experts by the time they're done.

Here are some activity ideas that'll get the job done:

• Have the students melt some ice and then boil off the resulting water. Sounds pedestrian, but measuring temperature changes and phase changes, and then relating those changes to what's happening at a "wiggly" molecular level, is a perfect way to hit this performance expectation. Afterward, just make sure to have the students graph their data and relate it back to what's happening to the particles.
• Divide students into small groups to create a skit that illustrates how kinetic energy is converted to thermal energy on a particle level. They can select whatever scenario they like, but should explain any changes in particle motion or movement in relationship to one another that occur during their scenario. Costumes are encouraged.
• Provide students with small manipulatives, such as differently colored beans or beads (use candy at your own risk). Then go through several different energy scenarios. Have them use their manipulatives to show the energy in the particles of each object you discuss and how that energy changes as the objects interact.

Disciplinary Core Ideas

PS3.A – 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.

Energy isn't some imaginary happy glow that happens when a Care Bear saves the day. Students should know that energy is a property that we can account for quantitatively.

The reason we can use actual numbers to account for energy is because we know that the energy in a system is conserved. That energy can be moved or transferred to different parts of the system, but it's not going anywhere. It's sort of like putting your entire paycheck into different savings accounts. You still have the same amount of money, it's just in different places (and not at Starbucks).

This concept should give students the general gist of how energy conservation works, but they may have trouble with the actual numbers part of it. Take your time and provide them with several different ways to deepen their understanding, including manipulatives, peer teaching, and simulations.

PS3.A – Definitions of Energy: At the macroscopic scale, energy manifests itself in multiple ways, such as in motion, sound, light, and thermal energy.

What is energy? Can we see it? How do we know it's there? We're not trying to get all philosophical on you, but these are valid questions (and ones that your sassier students might ask you to try and squiggle out of the lesson you had planned).

Students should know that we can examine energy on a microscopic scale by thinking about the movement of particles. Unfortunately, we can't really observe those particles, unless Santa brought you something really special this year (we know you're good, but were you that good?).

If we zoom out and take a look at energy on a macroscopic scale, we can observe the effects of these particles fox-trotting around in the form of motion, sound, light, or heat. This way is much easier on the eyes and the brain.

Students really shouldn't take an issue with this information since they experience it all the time. Again, they're probably not used to thinking of things in terms of energy, but some group brainstorming is a great way to get their energy juices flowing.

PS3.A – Definitions of 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.

When we decide to take a look at energy on a microscopic scale, we're going to be thinking about it in terms of lots of particles dancing a jig around each other. Students should know that the motion of these particles and where they're hanging out in relationship to other particles determines whether the energy will show up as light, heat, motion, or sound on a macroscopic scale.

Students should also know that force fields act as sort of a go-between for particles. It's a way for energy to be moved from one place to another without actually needing particles to bang into each other.

This includes the electromagnetic spectrum, which is made up of different wavelengths of energy that are capable of moving energy, even without a medium made up of other particles. For example, we can see stars because wavelengths of light traveled through the vacuum of space all the way to our eyes here on Earth.

When you start talking about particles you can't see, students are likely to get a little cross-eyed. Don't panic. Try to put them in expert-novice groupings so they can take advantage of each other's knowledge and encourage them to use their models to deepen their understanding.

Science and Engineering Practices

Developing and Using Models: Develop and use a model based on evidence to illustrate the relationships between systems or between components of a system.

When we start talking about energy on a particle level, we stop being able to see what's going on. We could just use our imaginations, but somehow we don't think there are a bunch of particles riding unicorns and jousting with laser swords. Better stick to the scientist route and make a model.

Students will turn up their inner scientist to develop a model that helps them understand how the energy they observe on a macroscopic scale is a result of particle interactions on a microscopic scale. Drawing, diagrams, animations, and computer simulations are all great ways to go here, since we want them to be able to see particles getting jiggy.

Crosscutting Concepts

Energy and Matter: Energy cannot be created or destroyed—only moves between one place and another place, between objects and/or fields, or between systems.

This is a popular concept around these parts. Students need to understand that energy doesn't get created or destroyed. There's no randomly appearing or disappearing of energy, no poofs of smoke, or invisibility cloaks involved.

Energy gets around by moving from one place to another, transferring between different objects, or dodging in and out of systems. Electric potential energy gets turned into current by moving electrons around. Heat gets transferred by particles bashing into one another. And so on.

So remind students that the next time they plug in their phone, it's not magically being juiced up; there's a transfer of energy happening right before their very eyes.