Getting Started

For these activities concerning symmetric shapes and lines of symmetry, you and each child will need a photocopy of the reproducibles included with this lesson.

What Is Symmetry?

Distribute a photocopy of the dot paper reproducible to each child and show the class how to fold the paper in half lengthwise along the center line. Indicate where the fold is and ask children to run their fingers along the fold on their dot paper. Keep the paper folded in half and demonstrate how to cut out a triangle, leaving the uncut fold as one side. Ask students to do the same. (You may wish to display the cut paper on an overhead projector if you are working with a large group of children.) Before children unfold their papers, challenge a volunteer to draw a picture on the chalkboard of how he or she thinks the figure will look once the paper is unfolded. Then have children unfold their papers to see what figure was created. Ask students to tell how the halves on both sides of the fold are alike. (Possible response: Both halves show triangles that have exactly the same shape and the same size.) Explain that when the halves on both sides of a line match in shape and size, we can say that figure is symmetric and we can call that line a line of symmetry.

Drawing Lines of Symmetry

Cut out the heart outlines on the hearts reproducible. Choose one of the larger hearts and challenge a volunteer to draw on it a line of symmetry.
Point out that the halves on both sides of this line of symmetry match. Ask children if they remember the word that describes a figure whose halves match when it is folded in half (symmetric). Cut out one of the leaf outlines from the leaves reproducible and draw a line across its center widthwise.
Ask children to explain whether this is a line of symmetry and if the figure is symmetric. (It is not a line of symmetry because the halves on either side of the line are not the same. Therefore, the figure is not symmetric.)
Distribute to each child a copy of the hearts reproducible and the leaves reproducible. Ask children to use a ruler to draw a line of symmetry on each heart and leaf outline. Then have children compare lines and either agree or disagree with each other's choices. Discuss any discrepancies.