Attributes of 3D Shapes Part 2
Objective
Big Idea
Warm Up
I begin today by reviewing the terms we use to describe attributes of 3D shapes. I hold up a rectangular prism and ask if anyone can remember what the shape is called? Next I ask if anyone can touch a face on the shape? What about an edge? A corner? A vertex?
I hold up a cylinder, a square pyramid, and a cone and repeat the process.
I then ask if anyone would like to describe a 3D shape for the class to guess? I take a volunteer to come up and describe a shape that they secretly show to me before they begin. I remind them that they will need to give at least 3 clues. After the student gives the clues they ask if anyone can come up and find their shape. We do this 3 times.
Next I ask each table to go up and find the shapes that they built the day before. I help with this process by finding the side of the shape with the name on it, and putting that side face up.
Teaching the Lesson
I post a table on the Smart Board, and give each child a copy for their desk. I tell them that today we will compare the 3 shapes they have. (They built a square pyramid this morning as they arrived at school so they now have a cube, a triangular pyramid and a square pyramid.)
I ask students to pick up the cube and count the number of faces they see and record it on the chart. Next we review the term vertex (corner) and I ask them to count those. We count the number of edges and record that. We repeat this with the other 2 shapes.
I ask students to look for patterns. What do they notice about the shapes, the different numbers of edges, vertices and faces. Do they see any patterns in the numbers of edges, faces or vertices from one shape to another? They should see patterns such as the numbers of vertices and faces are the same for the pyramids. I am asking students to construct viable arguments for what they are noticing (MP 3).
Now I give each student a straight edge. I ask them to measure 1 edge of the cube and write down the number in inches. (It is important to remind students to measure precisely so they can see that all the edges of a cube are the same size (MP6). I ask them to do the same with centimeters. Do they think that all edges will be the same for the cube? I ask them to check.
We repeat this for the square and triangular pyramid. What did they find out?
Closing
Once the students have completed the table we post their count of faces, vertices, edges and lengths on the board. I ask students to look for patterns in the results.
See: Identifying Patterns.
The students share their thoughts about the numbers they see on the board. Most of the patterns had to do with the types of numbers such as even numbers for the triangular prism, finding that the numbers changed by 1 (4 to 5), that there were 2 fours and an eight, etc. I hoped that students would notice that the number of faces and vertices were the same, while the number of edges was greater. I asked some questions to bring out this idea such as which are there more of in a shape, faces or edges? Why might that be? Students were able to identify the answer and give a plausible reason, such as you need an edge to connect every two faces and the faces on the ends so there have to be more edges. (MP3).
After the students point out the differences and patterns, I ask, how many sides does a triangle have (3), how many faces does a triangular prism have (4). How many sides does a square have (4), how many faces does a square prism have (5). If that is true can you guess how many faces a pentagon pyramid might have (6). How do you know that? (the pentagon has 5 sides).
We finish by sharing how a cube and a rectangular prism are similar and different.
