Overview

In Lesson 5, students compare two different kinds of materials for making mechanisms: pegboard and cardstock. Then they create cardstock models of their pegboard mechanisms. Finally, they look at other examples of modeling, and explore how a model is both similar to, and also different from the real thing. 

Materials

• Children’s Mech-a-Blocks constructions from previous lessons
• Classroom set of cardstock Mech-a-Blocks

Procedure

1.      Comparing materials: Distribute the mechanisms from previous lessons. Provide each group with some of the cardstock Mech-a-Blocks shapes.

• How are these cardboard pieces similar to the pieces you have been working with? How are they different?
• What would happen if I made a mechanism out of these cardboard materials?
• What would be better about mechanisms made from cardboard?
• What would be better if I made them from pegboard?

2.      Cardstock models of pegboard mechanisms. Review the diagramming activities from the previous lesson. Then present another idea for keeping a record of their work: “What if we had thin cardboard pieces in the same shapes and colors as the pegboard?”

Show them the shapes, strips and bases cut from cardstock.

• How could you use these pieces to make a model of your mechanism?

They could attach these pieces with fasteners, and make them both look and work like what they made in pegboard. These cardstock shapes are plentiful, so they could take these models home, and even take extra cardstock home to make new mechanisms.

Provide cardstock shapes and fasteners, and allow students to construct models of their original constructions:

Use this cardstock to make a mechanism that moves the same way as the one you made before, although it is made of a different material.

3.      Improving the accuracy of the models. The models students make at first will probably not be very precise. Use some of the students’ examples to highlight this problem. If necessary, take them apart, and hold similar pieces one on top of the other to demonstrate the differences in hole locations.

• Why doesn’t this model work the same way as  the original?
• Why is it important for the holes to be in the same places in the model as in the original?”
• How could we make sure to put the holes in the same places in the model as in the original?

4.      Science Notebook.  Use words and pictures to show how you made your model

5.      Discussion of models. In a brief whole-class wrap-up discussion, ask students for examples of models. They might suggest model cars, planes or boats; doll houses, clothing or furniture; stuffed animals; etc. If they don't include the mechanism models they have just made, ask if those should be added to the list. Then construct a class chart showing how each type of model is similar and different from the original.

Finally, conduct a brief discussion about these topics:

• Were the new models better than the first models? How could you tell?
• What made the new models better?
• What is similar between the model and the original mechanism? Why are these similarities important?
• What is different between the model and the original? How important are these differences?
• What is a model good for? 

6.      Outcomes

Students should be able to construct a cardstock model of a pegboard mechanism, and be able to compare the operation of the model with that of the original, listing pros and cons of each.

7.      Assessment

Show students a pegboard mechanism, accompanied by an accurate cardstock model.

• How are these similar? How are they different?
• What is better about each one? What is worse about each one?

Show students a pegboard mechanism, accompanied by a cardstock model that has some incorrect hole locations.

• How are these similar? How are they different?
• If I wanted my model to work more like the original, what would I need to do?