Shapes: Faces, Edges, Corners and Building Shapes
What this lesson covers
- 2D shapes are flat. 3D shapes are solid.
- 3D shapes have faces, edges and vertices (corners).
- A shape stays the same shape when you turn it.
- Small shapes can join to make a bigger shape.
Flat shapes
- 2D shapes are flat, like a drawing on paper.
- Count their sides and corners.
| Shape | Sides | Corners |
|---|---|---|
| triangle | 3 | 3 |
| square | 4, all the same length | 4 |
| rectangle | 4 | 4 |
| circle | 1 curved line | 0 |
Words for solid shapes
- 3D shapes are solid. You can pick them up.
- A face is a flat side. An edge is where two faces meet.
- A vertex is a corner. More than one vertex are called vertices.
Look at some solids
- Count the faces, edges and vertices.
- Some shapes also have a curved surface.
| Shape | Like | Flat faces | Edges | Vertices |
|---|---|---|---|---|
| cube | a dice | 6 | 12 | 8 |
| cylinder | a can of food | 2, plus a curved surface | 2 | 0 |
| sphere | a ball | 0, just a curved surface | 0 | 0 |
Turn it, it is still the same
- Turn a triangle upside down. It is still a triangle.
- Stand a square on its corner. It is still a square.
- A can lying on its side is still a cylinder.
Try it: flat or solid?
Sort by one thing
- Pick one thing to look at, then sort.
- Does it have a curved surface? Does it roll?
| Question | Yes | No |
|---|---|---|
| Does it roll? | sphere, cylinder | cube |
| Does it have a curved surface? | sphere, cylinder | cube |
| Does it have vertices? | cube | sphere, cylinder |
Try it: curved surface or only flat faces?
Build and break shapes
- Push small shapes together to make a new shape. Try, turn and try again.
- Cut a shape into smaller ones and put it back.
| Put together | You can make |
|---|---|
| 2 triangles cut from a square | a square |
| 2 same squares side by side | a rectangle |
| 4 same squares in 2 rows | a bigger square |
Common mistakes
- A square standing on its corner is not a square any more.It is still a square. Turning a shape does not change it.
- A cylinder has corners.A cylinder has 2 curved edges and no vertices.
- A cube has 6 corners.A cube has 6 faces and 8 vertices (corners).
- A circle and a sphere are the same.A circle is flat (2D). A sphere is a solid ball (3D).
Your turn
1
How many faces does a cube have?
2
How many vertices does a sphere have?
3
Which one rolls: a cube or a cylinder?
4
A triangle is turned upside down. What shape is it now?
5
Two same squares are put side by side. What shape do they make?
Show answer
1. 6 2. 0 3. The cylinder 4. A triangle 5. A rectangle
What to take away
- 2D shapes are flat; 3D shapes are solid.
- Faces, edges and vertices describe solids.
- Turning a shape does not change it.
- Small shapes join to make bigger ones.
Report a mistake
More in Geometry
Is your child on track?
Take the free placement test