Overview and Learning Objectives
Using a computer model of a bouncing ball, students are introduced to the idea of computer modeling, its limitations, and its advantages.
They can experiment with the elasticity of the ball to model balls with different "bounciness," ultimately ending with the understanding that there could be a super-superball, which never loses any of its "bounce" (or kinetic energy). This kind of behavior is very similar to that of atoms, so the model of a superball can be set in such a way as to model the behavior of a single atom.
Students will be able to:
- using a computer model, demonstrate the necessary conditions for having an atom/ball not convert any kinetic energy to other forms;
- predict the behavior of an atom with 100% elasticity that is set in motion;
- investigate two characteristics that affect the kinetic energy of an object;
- describe how the motion and mass of an atom correlates with a graph of its kinetic energy;
- describe two different kinds of modeling, one which is an idea or theory, and one which is something that acts out the idea or theory.
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This is the first in a series of computer-based activities that explore the molecular nature of biology. Because it is the first model students will use, there are meta-goals for this activity beyond the simple content of modeling a superball/atom.
This model was chosen to highlight several things:
- That computers can model reality (e.g., the behavior of a superball).
- That computers can model things we can't see because they're too fast, too slow, too big, or too small (e.g., the behavior of atoms and molecules).
- That models have limitations, but can still make useful predictions.
- That atoms conserve all of their kinetic energy (energy of motion) during collisions.
- If an atom is given an initial velocity, it will continue to move forever.
We start with a simple model of a single atom bouncing around because students need to have the core understanding that all atoms and molecules are in continual motion, and that they don't just "slow down" as is our everyday experience with moving objects. The only reason a real rubber ball stops bouncing is because some of its kinetic energy (energy of motion) is being converted into other forms of energy, like heat or sound. You can, therefore, make connections to energy conservation in this activity as well. Later this may be useful when discussing the conversion of chemical energy (as in ATP) or light energy (as in photosynthesis) into other forms of energy for proper cell function.
The computer model can be used alone, but it is best utilized in the context of other activities to reinforce the ideas mentioned above. One suggested sequence for integrating the computer lab in a wider modeling context would be the following:
Part A: Observing Real Bouncing Balls
- Explain to students that everything is made of atoms and that they need to know how those atoms behave in order to understand the world around them. Because atoms are too small to handle individually, they will use bouncy balls to explore some simple behaviors of atoms. Balls behave very much like atoms.
- Ask students to brainstorm different kinds of energy that they know about and list these on the board.
- Explain that the energy of motion is called kinetic energy and that one kind of energy can be converted to another (such as heat or light), but that it is never created or destroyed.
- Drop a ball in front of the class and let it bounce for a while.
- Ask the students why the ball stops bouncing. Ask for ideas and get into a discussion of where the energy goes if total energy must be conserved.
- Collect enough rubber balls of varying size, mass, and bounciness for the class to experiment with. Hand out the Kinetic Energy Lab (http://www.concord.org/~barbara/workbench_web/unit1/AdditionalMaterials/pdf/SuperballLab.pdf) and have them answer the questions.
Part B: Using the Computer Model
- Have students run the computer model Superballs are Like Atoms.
- They should see a table of contents appear. Have them click on each of these links.
- When they get to the "Summary" link, all of their questions and answers will be summarized. This may be a good point to review the activity with the class. By pressing on the printer button on the lower right corner of the summary page, they can save and print these questions and answers.
Part C: Kinesthetic Modeling
- Explain that students are going to do "kinesthetic modeling," which will involve them acting like superballs or modeling superballs with their bodies. Ask them to describe how a person would move if they were pretending to be a superball rolling around in a box lying on a table. List the rules the class comes up with. (They should have things such as: the person should move in a straight line until they hit a wall; the person should bounce off the walls; the person should slow down a little bit each time they bounce off; the person should convert some of their kinetic energy into other forms of energy; etc.)
- Set up the class such that most of the students form a square.
- Have one student be the super ball, and tell him or her to follow the rules the class listed for how a superball should behave.
- Discuss with the students the various models they have seen today, both the computer model and the kinesthetic model. Some suggested questions would be:
- How were they different or the same?
- What limitations do they both have for "really" modeling atoms and/or superballs?
- And finally, ask them what would happen if you had a bucket full of superballs that behaved like single atoms (never losing any kinetic energy), and you threw that bucket of balls out into the classroom. What would they see?
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