This activity prompts students to compare four shapes. It gives students a reason to use language precisely (MP6). It gives the teacher an opportunity to hear how students use terminology and talk about the characteristics of the items in comparison to one another. During the discussion, ask students to explain the meaning of any terminology they use, such as sides, corners, quadrilateral, and pentagon.

• “¿Por qué las 4 van juntas?” // “Why do all 4 go together? (They are all shapes. They have straight lines. Their sides touch each other to make corners. The number of sides matches the number of sides for each shape.)

The purpose of this activity is to encourage students to observe attributes of shapes and use them to sort shapes into groups. When students sort the cards, they look for common attributes or structures shared by different shapes (MP7). Students notice that there are multiple ways to categorize the shapes and that a shape may belong to more than one category depending on the attributes used to sort.

In grade 2, students refer to right angles as square corners. In this activity, students learn to use the terms angle in a shape and right angle in a shape to describe the corners of shapes. Note that the term “angle” is understood informally and used only in reference to shapes and their geometric attributes (for instance, students distinguish squares from other rhombuses). They will not learn the formal definition of an angle—a figure made up of two rays that share the same starting point—or that it is a measurable attribute until grade 4.

When students consider the language they use and revise it to describe a shape in detail or with more specificity, they attend to precision (MP6).

The cards in this activity will be used again in centers.