I have several sets of these 32 MiniRelational GeoSolids.
I mix them all together when we do an activity in which students sort the shapes into groups that illustrate the characteristics of similar and congruent. There are very few concrete materials that help students think about the difference between the properties of these two concepts.
In grades 4-6 you can also introduce the mathematical symbols for congruent and similar:
|Congruent (same shape and size)|
|Similar (same shape, different size)|
How about having that mathematically talented group of students in your class create an anchor chart for the class that compares the properties of congruent and similar.
Here is an interesting anchor chart that I found on Google Images. Let student research the meanings of the markings on the triangles and explain the definitons of the words proportional and adjacent. (Don't worry about the calculations at the bottom, just use the illustrations.)
What do you think about this idea? I had 3 very mathematically talented boys in my 3rd/4th grade class one year that kept me up at night thinking of challenging activities for them to do or investigate. (They loved geometry concepts, and I heard that one of the boys later became an engineer :) )When we would cover our "grade level" material, I would meet with them 8 minutes before class and discuss the lesson. Then using white boards or concrete materials, they would show me that they understood those concepts.
Next, I would give them their assignment, discuss the quality of work that I was looking for, and they would work and write in their math journals at the reading table in the back of the room. I can only tell you that the quality of work that came from those boys was worth the sleepless nights and extra work.