Grade 2: ConGruent 2-D Shapes

Comparing Spatially and identifying Congruence

Click Here: Printable Lesson Plan

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Content

Expectation:

E1.3 identify congruent lengths and angles in two-dimensional shapes by mentally and physically matching them, and determine if the shapes are congruent

Key Concepts

Two shapes are considered to be congruent if one can be transformed into the other through a series of flips, slides and/or turns. One fits exactly over the other (in the case of 2-D shapes).
The word congruent is used to describe not only the whole shapes, but also specific components of shapes, such as sides and angles.
Congruence can also be found within a single shape. For example, an equilateral triangle has 3 congruent sides and angles.

Learning Goal

We want students to

Understand congruence by comparing 2-D shapes spatially and measuring side lengths

Success Criteria

I know how to superimpose shapes to determine congruence
I can measure side lengths to identify congruence.
I can identifying if angles in two different shapes are the same

materials

Rulers
Explain Everything App

Minds On

Show students the following BLM 1.1 or give them a copy.

Have them “Guess” if the shapes are congruent, without using the word. No measuring, they will be using their eyes. Discuss their “guesses” and introduce the word congruent after they are done.

Action!

Pose Question: How can we prove those shapes are congruent?

Collect student responses and ensure they come to two of these conclusions.

Answer: Superimposing or measuring corresponding sides and angles.

Superimposing

The easiest way to test 2-D shapes for congruence is simple to put one shape on top of the other to see if the outlines can be made to match exactly.

Measuring Corresponding Sides and Angles

A more sophisticated strategy (and one that works for shapes in any orientation) is to measure the sides and angles in both shapes and compare the results. With congruent shapes, all the corresponding side lengths and angle measures will match.

Now students will take those shapes on the BLM and do just that. Cut them out and measure.

Consolidation Ideas

Create this with your students.

(App: Explain Everything)

Together as a class construct a T chart of what defines congruence and what doesn’t when comparing shapes.

Teacher Notes:

You are defining what congruence is and ruling out similar.

You are using specific language and examples in your t-chart

For Distance Learners

Digital Resource on Congruent Shapes

Independent Task / Assessment Opportunities

Independent Task / Assessment Opportunities:

Source: Which One Does Not Belong Website

Students need to complete the exit ticket questions BLM 1.2 and use reasons from the T-Chart compiled in the consolidation, to explain their math thinking.

Game: https://www.sheppardsoftware.com/mathgames/geometry/shapeshoot/SSCongruentSimilar.htm

(Needs adobe flash player)

Student Self Assessment (French and English)

Teacher Rubric: https://docs.google.com/document/d/1C28aCyHpZFAwz6C7AGxu_hAvPTSUKbHtNvH3R-d9yDM/edit?usp=sharing

Technology

Explain Everything App

ADDITIONAL RESOURCES

Source: J.Moss, C.Bruce, B.Caswell, T.Flynn, Z.Hawes (2016) Taking Shape: Activities to Develop Geometric and Spatial Thinking: Grades K-2