Author: Carin Helfer
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Participants must design special shoes using old shoes, plastics, rubbers, and duct tape. The shoes will be used for walking on an imaginary planet that has a very brittle, thin crust. In this activity, eggs will be used to model the surface of this planet, since the thin crust is not available for evaluation. Therefore, the success of the designed shoes for walking on the planet will be tested by walking on eggs.
The Best Teaching Practice, "Use of Models", will be followed.
The Physical Sciences Content Standard of Motions and Forces will be included with a discussion of the difference between force and pressure.
The participants will work in groups of 4 or 5. Before obtaining materials, the facilitator needs to determine the number of participants and thus, the number of groups.
The following items can be obtained from a craft store:
The following are packing materials that can be purchased at office supply stores, do-it-yourself moving companies, or shipping outlets. If you know anyone that has moved or receives many shipped items, they may be willing to donate some of these items.
The next item can be found at a home improvement store or craft stores.
Any other plastics and rubbers that the facilitator has available that appear manageable for cutting and building shoes.
All of these items are not necessary. The facilitator can also collect packaging items, such as food packaging, which would reduce the overall cost of the module. Purchasing items may allow a different range of materials to be used. Select a variety of items that includes different types of polymers, for example, polystyrene and polyester. Leftover materials can be divided up among participants that would like to complete this activity in class.
Overall total cost of this module will depend on the materials that are purchased for designing the shoes. At the minimum, $2 per group will be necessary for the eggs. $35 is sufficient to purchase items for 3 groups. If cost is a factor, larger groups could be used. Costs could be reduced by having participants bring some/all of the materials ahead of time.
Plastic eggs could be used, if desired.
The facilitator places an open egg carton on the ground and asks, "If I step on these eggs, what will happen? Why would we want to try this activity? What could we learn from doing this activity?"
Next, pose the problem and the use of eggs to model the surface of an imaginary planet:
The participants are to imagine that they will be traveling to an imaginary planet that has a very brittle, thin crust. In order to walk on the planet's surface, they need to have special shoes designed. Unfortunately, the brittle, thin crust is not available for evaluating on Earth. However, eggs that have similar properties to the planet's surface can be a model, or representation, of this planet's surface.
The participants can be divided into groups of 4 or 5, with each participant given a job in the group. For example, participants can obtain the materials, draw the design, or cut the materials. All of the participants can help with the assembly of the shoes.
Next, present the various materials that can be used for the shoes. Let the participants handle the various polymers and discuss the physical appearance. They should observe that although the materials are all various polymers, they have different properties. A variety of responses are possible based on the participants' observations. See the Explanation of Science section for more details on polymer properties. The facilitator can suggest that the groups think about which materials would be best suited for the shoe design that they will use? Why?
Some other possible topics that can be discussed within the groups are:
Is the size of the shoe important? Why?
What are other factors that might be considered to be successful? For example, graceful gate, smooth surface, non-sticky bottom.
Remind the groups that the desired result is to walk on the planet's surface. This goal will be evaluated using the eggs as a model and attempting to break the least amount of eggs.
Assessment: Informally monitor the participants' responses to the initial questions to see if they are logical.
After discussing these questions, the groups should design and build the shoes. The groups should determine which group member will wear the shoes and walk on the eggs.
Finally, test the shoe designs of each group. Each group has a member of their group walk on the eggs. For the actual test, two open cartons of eggs should be positioned on the ground to allow the group member wearing the designed shoes to step on the eggs when taking a few steps. The facilitator should record the number of broken eggs for each group.
The following information should not be disclosed ahead of time, only if and when necessary:
Since the pressure on the eggs should decrease with the size of the bottom of the shoes, a group may create a shoe that has a very large contact area. If this area is larger than the size of the eggs in the carton, this decrease in pressure will not be effective. Therefore, 2 or more egg cartons may need to be placed together for 'one' step.
Assessment: Monitor the discussion of the different polymer properties. Observe and note if all of the participants are involved in designing/building the shoes.
Each group explains to the other groups how they decided on the design of their shoes. What influenced their choice of materials? Did the group obtain the desired results?
The facilitator should briefly discuss polymers and some property differences.
Now, the facilitator can clarify the difference between force and pressure. This information answers the question above "Is the size of the shoe important?" See the Explanation of the Science Section for details.
To aid in understanding the concept of force and pressure, the facilitator should provide instruction for the calculation of pressure when force and area are known.
Pressure (as pounds per square inch) = Force / Area
Assessment: Check calculations of pressure. Are the new terms (polymers, force, and pressure) being used appropriately?
The participants should review the new information that was obtained from the actual testing of the designed shoes. If you did this activity again, what might you do differently? Were the groups pleased with their shoes?
Discuss the use of the eggs as the model for the planet's surface. Can the groups think of other possible use of models?
Have the participants develop a lesson plan for incorporating models into their teaching.
Assessment: Have the participants calculate the pressure for their shoe using the weight of another group member. Note: the area will remain the same so this number does not need to be recalculated.
Use of this module will enhance the facilitator's ability to help the participants to understand the Best Teaching Practice, "Use of Models". In this teaching practice, a material that is not available for evaluation purposes is modeled by using another material that has similar properties. This module uses eggs to model the surface of an imaginary planet that has a very brittle, thin crust.
Participants are given the challenge to design special shoes that can be used for walking on an imaginary planet that has a very brittle, thin crust. Since the planet's surface is not available to test the shoes, eggs, which have similar properties to the imaginary planet's surface, are used to test how well the designed shoes will work on the planet.
The difference between force, defined as pounds, and pressure, defined as pounds per square inch, will be presented. This module will enhance participants' understanding of the Physical Sciences Content Standard of Motions & Forces.
The materials available for building the shoes are plastics and rubbers, which are different types of polymers that have different characteristics. Participants will have the opportunity to see these different polymers and discuss the observed variations.
As a result of their activities in grades 5-8, all students should develop an understanding of
Professional Development Standard B:
Professional development for teachers of science requires integrating knowledge of science, learning, pedagogy, and students; it also requires applying that knowledge to science teaching. Learning experiences for teachers of science must
Lesson time: 60 - 90 minutes, depending on how lengthy the discussion times become. Longer discussions would be encouraged. In addition, facilitator may want to set the time allowed for building the shoes. 30 minutes is a reasonable amount of time. If too much time is allowed or no ending time is given, some groups may finish and need to wait for other groups that will be continuing to perfect their design.
Set-up the following stations with the appropriate materials in the classroom:
Care needs to be taken cutting with the scissors. Raw eggs occasionally may contain the Salmonella bacteria. Therefore, use the following safe handling practices for eggs: Wash hands and surfaces that have contacted the broken eggs with hot, soapy water or a commercial antibacterial cleaner.
Ask the participants to share (orally or in writing) ideas for other models that they could use with their classes. The participants should discuss the implementation of this activity in their classrooms. The facilitator should monitor the discussions of implementation.
Polymers, which are long chain molecules that are made of building blocks known as repeating units, are encountered by us everyday. The materials that are commonly referred to as plastics and rubbers are polymers. Since the repeating units can be composed of various elements that can be combined in a variety of ways, a number of differences can be observed between different types of polymers. Also, the method of processing can vary the physical properties. The following terms may be used by the participants to describe the different polymers available:
elastic, stiff, opaque, transparent, rubbery, soft, hard, flexible, fibers, foam
Pressure is the force (defined as weight) divided by the area (defined as square inches). In other words, pressure is the amount of force exerted over a given area. Therefore, if you have two shoe designs with one design twice as large as the other design, the larger shoe will exert less pressure on the eggs than the smaller shoe. An example to help understand the difference of force (pounds) and pressure (pounds per square inch) is a woman walking on soft ground in a high, narrow heel. As she crosses the ground, her heels sink into the ground. Frustrated, she changes her shoes and puts on tennis shoes that have flat-bottoms. Now she can easily walk across the ground without sinking. Her weight (force) is the same regardless of the shoe. But, with the high-heeled shoe, the area of the shoe bottom is smaller than the area of the bottom of the tennis shoe. When calculating the pressure as weight/area, this smaller area will result in a larger pressure. The pressure is much greater than the pressure with the tennis shoe because the force is exerted over a smaller area with the narrow, high heel.
None available for this module.
Some possible topics that can be discussed using the knowledge of force and pressure:
Some individuals may not want to destroy eggs. Plastic eggs could be used.
None available for this module
Physical science activities created for OSCI, summer 2005, in cooperation with Miami University, Center for Chemical Education
OSCI Materials are still available at Egg Walk Challenge Lesson Plan