Unit Plan 28 (Grade 4 Math): Classifying 2D Figures—Properties First
Classify 2D shapes by parallel/perpendicular lines and angle types; identify right triangles and describe quadrilateral properties using precise vocabulary, evidence, and models.
Focus: Classify two-dimensional figures by the presence/absence of parallel/perpendicular lines and angle types; identify right triangles and describe quadrilateral properties.
Grade Level: 4
Subject Area: Mathematics (Geometry—Properties of 2D Figures)
Total Unit Duration: 5 sessions (one week), 45–60 minutes per session
I. Introduction
Students use attributes of lines and angles to classify and justify categories of 2D figures. They practice seeing parallel and perpendicular relationships, recognizing acute, right, and obtuse angles, and identifying right triangles. Work centers on clear definitions, visible evidence, and precise vocabulary.
Essential Questions
- Which properties matter when classifying 2D figures?
- How do parallel and perpendicular lines help define quadrilaterals?
- How can angle types help me recognize a right triangle and sort triangles/other shapes?
II. Objectives and Standards
Learning Objectives — Students will be able to:
- Use parallel/perpendicular line tests and angle identification to classify 2D figures.
- Identify right triangles and describe how they form a category of triangles.
- Sort quadrilaterals (e.g., rectangles, squares, parallelograms, rhombi, trapezoids) by line/angle properties.
- Support classifications with evidence (marked diagrams, right-angle checkers, grid/dot paper).
- Communicate reasoning using precise vocabulary and address misconceptions.
Standards Alignment — CCSS Grade 4
- 4.G.2: Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or on the presence or absence of angles of a specified size; recognize right triangles as a category, and identify right triangles. (Connections: 4.G.1 for line/angle vocabulary; 4.MD.5–7 for angle understanding.)
Success Criteria — Student Language
- I can name the properties I used (e.g., parallel, perpendicular, right angle) to classify a shape.
- I can prove a right triangle using a right-angle checker.
- I can explain why a shape belongs/does not belong in a category, using evidence on my diagram.