# Lesson 3

Shapes That Are Flat

## Warm-up: Which One Doesn’t Belong: All the Shapes (10 minutes)

### Narrative

This warm-up 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 characteristics of two- and three-dimensional shapes.

### Launch

• Groups of 2
• Display the image.
• “Pick one that doesn’t belong. Be ready to share why it doesn’t belong.”
• 1 minute: quiet think time

### Activity

• 2–3 minutes: partner discussion
• Share and record responses.

### Student Facing

Which one doesn’t belong?

### Activity Synthesis

• “Let’s find at least one reason why each one doesn’t belong.”
• “What solid shapes do the images for A, B, and C show?” (cube, cone, and cylinder)
• “Does D show a solid shape? Why or why not?” (Maybe it is supposed to be a sphere. It looks like it is just a circle.)
• “A circle is not one of our solid shapes. We call it a flat shape.”

## Activity 1: Card Sort: Flat Shapes (15 minutes)

### Narrative

The purpose of this activity is for students to sort two-dimensional shapes into categories that make sense to them. As students sort, they may sort by defining attributes such as number of sides or corners. Some students may sort by the name of the shape. Somes students may sort by non-defining attributes such as color or size. Students may have leftover shapes depending on how they sort. As students work, encourage them to refine their descriptions of the shapes using more precise language and mathematical terms (MP6). Students' sorts are displayed for the gallery walk in the next activity.
MLR7 Compare and Connect. Synthesis: Lead a discussion comparing, contrasting, and connecting the different ways pairs sorted their cards. Ask, “What was the first way you sorted your cards?” “What was the second way you sorted the cards?” and “How were the two ways you sorted similar and different?” Advances: Representing, Conversing
Engagement: Develop Effort and Persistence. Chunk this task into more manageable parts. Give students a subset of the cards to start with and introduce the remaining cards once students have completed their initial sort.
Supports accessibility for: Conceptual Understanding, Attention

### Required Materials

Materials to Copy

• Flat Shape Cards Grade 1

### Required Preparation

• Create a set of Flat Shape Cards from the blackline master for each group of 2.

### Launch

• Groups of 2
• Give each group a set of shape cards.

### Activity

• “With your partner, sort your shape cards into groups. Give each group a category. Remember, a category is a label that tells how objects in a group are alike. Explain each category you made. Then sort the cards in a different way.”
• 10 minutes: partner work time
• “How might you describe this shape?”
• “Why did you place this shape in this group?”
• “Why didn’t you place _____ with this group?”

### Activity Synthesis

• “What words did you use to explain how you sorted the shapes?” (Number of points, sides, corners, name of shapes)
• Highlight the use of terms like triangle, circle, rectangle, square, hexagon, corners, and sides.

## Activity 2: Shape Sort Gallery Walk (20 minutes)

### Narrative

The purpose of this activity is for students to participate in a gallery walk in which they see a variety of ways the flat shapes have been sorted. Student discuss with their partner what they notice about how their classmates sorted the shapes (MP3).

### Required Preparation

• Display each group's work from the previous activity.

### Launch

• Groups of 2
• “We are going to do a gallery walk to look at different ways we have sorted the flat shapes. Talk with your partner about what you notice about the work. See if you can tell how they sorted the shapes. Record how they sorted in your book.”

### Activity

• 3 minutes: partner work time
• “Now we will all move so we can see how a different group sorted the shapes.”
• 3 minutes: partner work time
• Repeat as time permits.

### Student Facing

Group 1: They sorted

Group 2: They sorted

Group 3: They sorted

### Activity Synthesis

• “In what different ways did we sort the shapes?”
• As each different way is mentioned, ask the group that sorted in that way to explain how they decided which shapes belonged in each category.

## Lesson Synthesis

### Lesson Synthesis

Display Card A.

“Today we looked at flat shapes and described them in different ways in order to sort shapes. How might you describe this shape?” (There are three sides that are the same. There are three corners. It is a triangle.)

Display Card Q.

“How might you describe this shape?” (There are four sides. Three of the sides are the same length and the bottom side is long.)

Continue with shape cards U and C as time allows.