Although the principles of similarity and congruency share some elements, they differ slightly. Similar shapes share the same angle measurements and their sides relate proportionately, while congruent shapes share the same angle and side measurements.
You can use several coloring worksheets, based on worksheets found at Super Teacher Worksheets, to determine the difference between similar and congruent shapes. On the first worksheet, list pairs of shapes of different sizes. For some pairs, create the same shape, just in different sizes. For other pairs of shapes, differ the shapes slightly. For an example of dissimilar shapes, you might use a circle and an oval. For the congruent worksheet, create a match game where the students match 20 randomly placed shapes to their congruent counterpart (totaling 40 shapes on the worksheet).
Create a search game for individual students, where they go around their work area and find two similar shapes and two congruent shapes. For similar shapes, your students may choose a beach ball and a baseball or two cubes of different sizes. For congruent shapes, your students might choose two congruent pieces of paper, two cubes of the same size or two baseballs. For a more difficult assignment, encourage your students to list things they see on the way to and from school, and determine congruency and similarity.
Concentration, a popular children's card game, uses the matching of congruent shapes in order to win. To play this game, cut out square pieces of cardboard or card stock. Cut as many as you like, but make sure that you can put the total number of cards together into a square (4, 9, 16, 25). Draw pairs of congruent shapes, using markers, on each piece of cardboard or card stock, with each piece containing one shape. Place the cards in a square, face down, in front of the student and let her choose two cards at a time. Every time she chooses a congruent pair, those two cards are removed from the board. The child wins when she removes all cards from the board.