Download Classifying Figures

Lesson Seed: 5.G.B.4 Classifying Two-dimensional Figures by Attributes
(Lesson seeds are ideas for the domain/cluster/standard that can be used to build a lesson.
An effective lesson plan requires more components than presented in a lesson seed.)
Domain: Geometry
Cluster: Classify two-dimensional figures into categories based on their properties.
Standard(s): 5.G.B.4 Understand that attributes belonging to a category of two-dimensional figures also belong to all subcategories
of that category.
Purpose/Big Idea:
 Students apply geometric attributes to describe and categorize two-dimensional figures.
Materials:
 Sentence Strips, Cards with various two-dimensional figures, including various quadrilaterals
Activity:
 This is a concept attainment activity that will expose students to the hierarchical nature of how polygons are classified.
Display a large Venn Diagram. Select two attributes that are commonly used to distinguish polygons. Some examples could
be: all right angles, all sides are congruent, only opposite sides are congruent, or opposite sides are parallel.
 Write the two attributes selected on two sentence strips and attach to the Venn Diagram so that the writing cannot be seen.
 Provide each pair of students with a polygon represented on a card.
 For this example, the teacher has selected the attributes “all sides congruent” on the left, and “all right angles” on the right.
 The teacher begins the activity by placing a polygon on the Venn Diagram as shown below.
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All Sides Congruent
All Right Angles
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Student pairs will place their shape where they believe it belongs based on the shapes already placed. The teacher will
confirm that the shape is correctly placed, or if it should be moved.
If the next shape to be placed is a square, it would be placed in the center because both attribute descriptors are true (a square
has all right angles and all sides congruent).
As shapes are placed, students will begin to deduce the attribute descriptors and become more confident in where their shape
would fit into the diagram. Encourage students to discuss the placement of shapes with each other, or engage students by
having them create the diagram at their desks as the shapes are placed.
The picture below shows the Venn Diagram after several shapes have been placed.
All Sides Congruent
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All Right Angles
At this point students should be encouraged to state the attributes on the sentence strips and to support their thinking. The
teacher will flip the sentence strips so that the diagram is now labeled.
Note that many shapes are placed outside the diagram. Ask, “What other shapes would go outside of the Venn Diagram?”
Only the square is in the middle. Ask, “What other shapes could go in the middle of the Venn Diagram?”
Discuss why all rhombuses ended up in the left circle.
Note that all rectangles are in the right section. Discuss.
Discuss how shapes can be defined based on the classification information provided by the Venn Diagram.
Guiding Questions:
 Is a square a rhombus? Explain your reasoning.
 Is a square a rectangle? Explain why you think that.
 Are all rectangles parallelograms? Give examples to prove your reasoning.