This activity introduces three-dimensional solids with images meant to engage students with objects they may have previously seen. The activity invites students to name and describe similarities and differences between the objects in the images.

Welcome any informal language students begin with to describe their thinking. Encourage students to refine their language (MP6) by using terms such as “base,” ”edge,” “vertex,” “face,” “curved,” and “pointed,” as well as the name of each shape, to describe each object they have seen in previous grades.

The goal of this discussion is for students to compare and contrast three-dimensional shapes and refine their ideas, using mathematical language.

Invite each group to share the set of images they chose as well as their similarities and differences. Record and display the responses for all to see. After each response, ask the class if they agree or disagree. Since there is no single correct answer to the question of what is similar and different, attend to students’ explanations and ensure the reasons given are correct. If the idea of cross-sections does not come up during the conversation, ask students to discuss this idea. Students will focus on cross-sections in future lessons, so there is no need to go into depth at this time.

During the discussion, prompt students to explain the meaning of any geometric terminology they use, such as “face,” “base,” ”edge,” “vertex,“ “pyramid,” “cylinder,” “sphere,” “prism,” and “cone,” and to clarify their reasoning as needed.

To involve more students in the conversation, consider asking:

• “How do you know ?”
• “What do you mean by ?”
• “Can you say that in another way?”

The purpose of this activity is to review the names of two-dimensional and three-dimensional shapes and their features (base, edge, face, vertices). Through this open-ended activity, students will recall language as they communicate similarities and differences with their new classmates.

As students work, encourage them to refine their descriptions of the shapes, using more precise language and mathematical terms (MP6).

This is the first Card Sort activity of the course. An important aspect of this routine is to allow students time at the start to sort the cards into categories of their choosing. This step gives students the opportunity to familiarize themselves with the content of the cards without the additional pressure of organizing them in a specific fashion. It also provides insight into the aspects of each card students attend to and the language they have to describe their observations.