In this unit, students will learn that geometric shapes have properties that allow them to be put into categories and subcategories. This unit extends students’ prior knowledge of using spatial reasoning skills to discuss and categorize twodimensional shapes. Students are likely to struggle with understanding that twodimensional shapes can be classified in more than one category and have more than one name.
Key Concepts:
 Figures have geometric properties that allow us to create categories of figures.
 Attributes belonging to a category of twodimensional shapes also belong to all subcategories of that category.
 Because figures may belong to categories and subcategories, we can classify figures in a hierarchy based on properties.
Prior Knowledge Needed:
 Shapes in different categories (rhombuses, rectangles, etc.) may share attributes; (Grade 3, Unit 13; 3.G.A.1)
 All rhombi, rectangles, and squares are examples of quadrilaterals, but not all quadrilaterals fit in those subcategories; (Grade 3, Unit 13; 3.G.A.1)
 Points, lines, line segments, and rays have specific properties; (Grade 4, Unit 10; 4.G.A.1)
 Two lines are parallel if they are on the same plane and will never intersect, and perpendicular if they are on the same plane and intersect at a 90degree angle; (Grade 4, Unit 13; 4.G.A.2)
 Triangles can be categorized based on their angle types; (Grade 4, Unit 13; 4.G.A.2)
Units on the Horizon:
 Problem solving with twodimensional figures (Grade 6, Unit 10)
 Problem solving with volume and surface area (Grade 6, Unit 11)
Lessons

Lesson objective: Understand that categories of figures are based on their geometric properties. Students bring prior knowledge from 3.G.A.1 that different categories of figures (rhombuses, rectangles, etc.) may share attributes, and that triangles can ...

Lesson objective: Create categories for sets of twodimensional figures. This lesson helps to build fluency with classifying twodimensional figures. Quadrilaterals are used here because they support student awareness of shared attributes. This work dev...

Lesson objective: Classify triangles by the lengths of their sides. This lesson provides practice with classifying twodimensional figures. Triangles are used here because they support students' understanding that twodimensional figures can be classifi...

Lesson objective: Extend understanding that in addition to categories of twodimensional figures, we can also have subcategories as well. Students bring prior knowledge of shapes in different categories (rhombuses, rectangles, etc.) sometimes sharing at...

Lesson objective: Practice creating and organizing categories and subcategories of twodimensional figures. This lesson helps students organize categories of twodimensional figures using a variety of attributes. Flowcharts and Venn diagrams used here b...

Lesson objective: Organize figures into categories and subcategories to understand the relationship between attributes. This lesson provides an opportunity for students to apply their knowledge and understanding of subcategories of twodimensional figur...

Lesson objective: Understand how categories and subcategories of twodimensional figures are connected. Students bring prior knowledge that figures in different categories (rhombuses, rectangles, etc.) may share attributes from 3.G.A.1. This prior knowl...

Lesson objective: Create and read charts that illustrate hierarchical relationships. This lesson helps to build fluency with the categorization of twodimensional figures. A flowchart is used here because it highlights the connected relationships of dif...

Lesson objective: Investigate categories and subcategories of quadrilaterals. This lesson provides an opportunity for students to apply their knowledge and understanding of shared attributes in a game situation. Students are asked to consider two catego...

Lesson objective: Draw figures with given attributes, including number of sides, measures of angles, and parallel or congruent sides. This lesson provides an opportunity to play a mathematical game where they attempt to draw figures with given attribute...