Lesson objective: Identify 2D and 3D shapes as flat or solid.

This lesson helps to build fluency with identifying dimensional shapes as flat and solid. 2D and 3D shapes are used here because it supports the idea that 2D and 3D shapes are flat or solid. This work develops students' understanding that 2D and 3D shapes can be identified as flat or solid.

Students engage in Mathematical Practice 7: Look for and make use of structure. Mathematically proficient students are able to look closely and use structure to identify, describe and create shapes as they explore 2D and 3D shapes to determine if they are flat or solid.

**Key vocabulary:**

**Special materials needed:**

- 2D shapes (attribute blocks, pattern blocks, etc.)
- 3D shapes