Lesson plan

Shape Detectives: What's in the Bag?

What's in the bag? This fun math lesson involves using defining attributes as clues to draw conclusions. Young learners will have a great time making guesses about different objects and creating their own shape riddles.
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Students will be able to identify and describe various shapes using defining attributes.

(10 minutes)
  • Gather students in a circle and hold up the shape bag.
  • Explain that this is a mystery shape bag that will be passed around. Students have to try to figure out what’s inside without peeking.
  • Demonstrate the procedure by closing your eyes, manipulating the bag with your fingers, thinking aloud about what you feel inside.
  • Pass the bag around the circle and ask each student to share one observation about what is felt.
  • Explain that our observations about what we feel in the bag are our first clues regarding what is inside. Add that more clues will follow as we open the bag and experiment with the shapes.
(10 minutes)
  • Take out one of the objects from the shape bag.
  • If this is a shape that was guessed, ask what made it easy to describe. If this was not guessed during the introduction, ask what made it hard to describe.
  • Ask if the color and size help to describe its shape.
  • Point out that any object can be red, blue, large, or small. The best clues use specific attribute descriptions.
  • Model a defining attribute description for one of the objects in the bag. For example: The triangle is closed, not open. It has three sides.
(10 minutes)
  • Explain that the class will now find more ways to describe the objects by seeing which ones roll.
  • Hold up the first item and ask students to predict whether or not it will roll. Tally the responses on the board under YES or NO.
  • Ask for volunteers from each response column to explain their predictions. Make sure they refer to defining attributes.
  • Model a response if needed, such as: The marble will roll because it has no corners to slow it down.
  • Release each item and ask students to check their predictions against the outcomes.
  • Ask: Any surprises? Why or why not? Emphasize using attributes to define results.
(15 minutes)
  • Give directions for the Name That Shape worksheet.
  • Circulate the room to monitor understanding as students work on the worksheet.
  • Enrichment: Challenge advanced students to create additional experiments to test for attributes.
  • Support: Allow struggling students to use manipulative shapes to help during Independent Working Time.
(10 minutes)
  • Distribute dry erase boards and markers.
  • Review shape recognition by giving clues and asking students to draw the corresponding shape on their boards and hold it up for a quick assessment.
  • For further assessment, collect the Name That Shape worksheet from students at the end of the lesson. Review the worksheets later.
(10 minutes)
  • Ask students to pair with a partner to share shape riddles. One partner gives clues about a shape, while the other tries to guess what the shape is.
  • Allot enough time for both partners to play each role.

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