Icebreaker: ask the students if they ever noticed how their actions are reversed in the mirror. Maybe have you tried to braid your hair using two mirrors and looking backward? It is difficult because what you are seeing what is called the "mirror image" of your self. Which is the opposite image (right is left / left is right).
Make sure that the class is divided evenly into pairs. Tell the students to face eachother and be eachother's "mirror image." Ask for a volunteer to come and demonstrate with the teacher (mirroring eachother's movement). Now ask the pairs to practice, and walk around monitorng the students to make sure they are doing the exercise correctly. Ask them, "when your partner moves his/her right arm...which arm are you using? The same or opposite? Yes that's right your left arm."
Now ask students to take their seats again. Write the word "congruent" on the board. Ask students if they know the meaning. Define congruent for the class.
con·gru·ent : /ˈkɒŋgruənt, kənˈgru-, kəŋ-/ Show Spelled[kong-groo-uhnt, kuhn-groo-, kuhng-] Show IPAadjective
agreeing; accordant; congruous. 2.
Mathematics . of or pertaining to two numbers related by a congruence. 3.
Geometry . coinciding at all points when superimposed: congruent triangles. Ask the students what might congruent shapes (like the triangles in the definition) look like? Ask them to think about their mirror image partner. "Yes, that's right congruent shapes or figures will have exactly the same size and shape." Draw two congruent triangles on the board. Now, pass out the five different shape templates you have pre-prepared. (Ex: a star, triangle, hexagon, rectangle and pentagon). Ask students to look at the figures and to draw them as exactly (same size) as possible on theur sheets of paper using a pencil. Ask the students to then cut out with scissors their shapes from the paper. Students will then get back together with their "mirror image" partner to match their congruent figure cut-outs.
Do they match? How close? Are they truly congruent? Ask the students to come back to their seats and discuss their findings and experience. Did the figures stay the same even when their position was changed? Explain that is called "transformation" (the change of position of a figure). Write this word and its definition on the board. Ask the students to copy down both terms and definitions onto their paper.
Then ask the students to trace one of their shape templates onto their paper. Instruct them to trace the same shape again in a different direction. Tell them, "notice that the size and shape did not change. The shape should still the same." "The shapes are congruent to eachother."
Now ask the students to choose a shape and trace it once. Then slide it over, up, or down at least two spaces on the graph paper and trace it again.
"Did the shape change?" Ask students to share their experiences.
Now ask the students to flip and turn their shape and see what happens. Discuss what happens for the students.
pass out a worksheet for class and/or homeowrk. Suggested format: worksheet can be four rows wide, by eight rows long. Each cell /row should represent a certain kind of shape (star, arrow, rectangle, square, etc.) in the same color but where the first column's figure will match to one other column, the other two look similar (all the same color) but slightly different shaped. The instructions should tell the students to look at the first shape in each row and find it's congruent pair in the same row. Tell the students they can use a ruler to measure if they like for shapes that look very close to identical. Use the completed worksheet to assess the students' overall understanding of the lesson.