Identify and Describe Two-Dimensional Shapes Unit of Study 10: Plane Shapes Global Concept Guide: 1 of 4

Content Development Students need opportunities to complete open sorts and define the categories in which they sorted prior to teachers having students sort based on specific attributes. Analyze classes of figures to determine new properties. Then name figures based on attributes. Vocabulary should be heavily emphasized throughout this Unit of Study. It is important to focus on the properties of the figures rather than on simple identification. As new geometric concepts are learned, the number of properties that figures have can be expanded.

Day 1  On Day 1, students begin to explore attributes of plane figures.  Have students explore a variety of plane shapes and discuss the attributes within each shape. For example, in the figure below students can identify line segments, angles, etc. Students need a conceptual understanding of these vocabulary words and a variety of experiences to discover them.  Excursions; The Shape of Things to Come p. 91 is good to use with this concept. Use precise vocabulary within this unit.

Day 2  How can you determine whether a plane shape is a polygon?  Provide students with a chart that is similar to the one below.  Have students determine what attributes make a plane figure a polygon.  Students should generate their own definition of a polygon using the examples and non-examples.  Ensure that students include vocabulary such as: Closed figure, line segments, vertices etc.  Have students use their definition of polygons to create and justify polygons either using Geoboards or Anglegs

Day 3  How can you describe a two-dimensional shape?  Go Math! Lesson 9.2 is an excellent resource to use on Day 3.  Students apply their understanding of the attributes of Polygons from Day 2 all two-dimensional shapes plane shapes.  Provide students various shape cards  Have students use their knowledge of various attributes of polygons to describe attributes.

Day 3 continued…  How can you describe a two-dimensional shape?  Shape Sort: Have students work in groups. Use two-dimensional shapes similar to the ones referenced below  Each student randomly selects a shape and tells two attributes of the shape.  Then students randomly select two shapes.  Their task to is find two attributes that the shapes has in common and two attributes that are different.

Enrich/Reteach  For students who are struggling with this concept, have them utilize the Reteach Activity on p. 381B. Students can physically build the polygon using the number of line segments indicated by the number cube to help make connections between attributes of polygons and names of polygons.  For students who need extensions, give them a variety of riddles. The Enrich activity on p. 381B is a great example of this. Students use their understanding of the attributes of polygons to decipher whether the statements classify a shape as a polygon.

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