Recognizing reflection symmetry

General

Students learn to recognize symmetry and reflection symmetry.

Standards

CCSS.Math.Content.4.G.A.3

Learning objective

Students will be able to recognize symmetry and reflection symmetry.

Introduction

Ask the class if they remember what symmetry is. Then they must drag the shapes to the correct box.

Instruction

Explain to students that a shape has symmetry if the image remains the same if you place a mirror in the middle of the object. If you don't have a mirror you could also fold it in half to determine if a shape has symmetry. Hand out a worksheet with a heart and a broken heart as well as a mirror. Both shapes have a dotted line. Ask students to place the mirror on the dotted line and to determine if the shape has symmetry or not. The whole heart is symmetrical, but when students try placing the mirror on the dotted line of the broken heart, they should see that it is asymmetrical- or does not have symmetry. Remind students that you could place the mirror on the line in two ways, to reflect the left or right side of the heart. Show that doing so does not make the shape symmetrical, but shows different results. Then show students more shapes and ask students to determine which shapes are symmetrical. Ask students to stand for symmetrical shapes and sit for asymmetrical shapes.
Then explain mirror writing to the class. Use a mirror to determine what is written. Ask students to practice mirror writing their name and have them check their writing with a mirror. Remind students that they have to write from right to left (rather than left to right as we usually write). Ask if students can determine what is written.

Check that students are able to recognize symmetry and reflection symmetry by asking the following questions:
- When is a shape symmetrical?
- What is mirror writing?

Quiz

Students are given shapes and must indicate which are symmetrical and which are asymmetrical. Students are also given mirror writing and are asked to determine what the written word is. They are also asked to sort shapes into symmetrical and asymmetrical piles.

Closing

Discuss with students that it is useful to be able to recognize symmetry and reflection symmetry. Ask students to determine which of the given images are symmetrical and which are asymmetrical.

Teaching tips

Students who have difficulty with symmetry and reflection symmetry can be supported by making use of a mirror. Give them symmetrical shapes with dotted lines so that they can practice recognizing that the shape remains the same when a mirror is placed on the dotted line. Then repeat with asymmetrical shapes.