Mathematics · 2nd Class · 3-D Shapes · Summer Term

Properties of 3-D Shapes: Faces, Edges, and Vertices

Discover the parts of 3-D shapes by counting their flat faces, straight edges, and pointy vertices.

TL;DR:Let's become shape detectives and investigate the secret parts of 3-D shapes. We'll look closely at everyday objects to discover their flat faces, straight edges, and pointy vertices.

• NCCA Curriculum Specifications
• PSMC: Shape and space - 3-D shapes - Explore, describe and compare the properties of 3-D shapes

About This Topic

This topic introduces second-class pupils to the fundamental properties of three-dimensional shapes, a key component of the Shape and Space strand in the Irish Primary School Mathematics Curriculum. Building on their prior ability to recognise and name 3-D shapes, pupils will now engage in a more analytical exploration, learning to identify and count the faces, edges, and vertices. The focus is on hands-on, tactile learning, using a variety of concrete manipulatives like geometric solids, building blocks, and everyday objects. This approach helps to move pupils from simple recognition to a deeper understanding of geometric structure.

The curriculum emphasises the development of mathematical language, and this topic is rich with opportunities to introduce and reinforce key vocabulary. By describing, comparing, and sorting shapes based on these new properties, pupils enhance their communication and reasoning skills. This foundational knowledge is crucial for later geometric concepts, including understanding shape nets, surface area, and the relationships between 2-D and 3-D shapes. The activities encourage a playful, investigative mindset, allowing pupils to discover geometric principles for themselves.

Key Questions

1. Identify the number of faces on a cuboid.
2. Explain what a vertex is using a pyramid.
3. Compare the number of edges on a cube and a cuboid.

Learning Objectives

• Identify and count the number of faces on common 3-D shapes.
• Identify and count the number of edges on common 3-D shapes.
• Identify and count the number of vertices on common 3-D shapes.
• Describe a 3-D shape using the vocabulary of faces, edges, and vertices.
• Compare two 3-D shapes based on their properties.

Key Vocabulary

3-D Shape	A solid shape that is not flat. It has length, width, and height.
Face	A flat surface on a 3-D shape.
Edge	The straight line where two faces meet on a 3-D shape.
Vertex	A point or corner where edges meet. The plural is vertices.
Cuboid	A 3-D shape with six rectangular faces, like a lunchbox.
Cube	A special 3-D shape with six identical square faces, like a dice.

Watch Out for These Misconceptions

Common Misconception

Pupils confuse edges and faces, often double-counting the line where two faces meet.

What to Teach Instead

Explain that a face is a flat surface, like the cover of a book, while an edge is the single straight line where two faces join. Use a physical model and trace one edge with a finger to show it is a single line.

Common Misconception

When looking at a 2-D drawing of a 3-D shape, pupils forget to count the 'hidden' faces, edges, and vertices.

What to Teach Instead

Always use physical 3-D models alongside drawings. Encourage pupils to hold and turn the shape in their hands, pointing to each part as they count to ensure none are missed.

Common Misconception

A sphere has one big face.

What to Teach Instead

Clarify that a 'face' in this context must be a flat surface. A sphere has a curved surface, not a flat face, so it has zero faces.

Active Learning Ideas

Stations Rotation

Shape Detectives

Pupils go on a 'shape hunt' around the classroom or school grounds to find real-world examples of cubes, cuboids, cylinders, and spheres. They bring the objects back and work in pairs to count the faces, edges, and vertices, recording their findings on a simple chart.

25 min·Pairs

Stations Rotation

Play-Doh and Stick Skeletons

Provide pupils with Play-Doh and cocktail sticks or straws. They use small balls of Play-Doh for the vertices and the sticks for the edges to construct 'skeletons' of shapes like cubes and pyramids.

20 min·Individual

Stations Rotation

Feely Bag Riddles

Place a 3-D shape inside an opaque 'feely bag'. A pupil reaches in without looking and describes the shape based on its properties, saying, for example, 'My shape has 6 flat faces and 8 pointy vertices'. The rest of the class must guess the shape.

15 min·Whole Class

Real-World Connections

• Looking at buildings and houses to spot cuboid and pyramid shapes in their structure.
• Stacking items in the supermarket, like cereal boxes (cuboids), which fit together perfectly because of their flat faces.
• Playing with toys like building blocks, dice, and footballs, which are all examples of 3-D shapes.
• Understanding food packaging, like a can of beans being a cylinder or a Toblerone box being a triangular prism.

Assessment Ideas

Quick Check

Teacher observation during group activities. Listen for correct use of vocabulary and ask pupils to 'show me a vertex' or 'count the faces on this box' to check for understanding.

Quick Check

Give pupils a simple worksheet with pictures of a cube, cuboid, and pyramid. Ask them to write down the number of faces, edges, and vertices for each shape.

Exit Ticket

Use an exit ticket where pupils draw a shape and label one face, one edge, and one vertex to show what they have learned.

Frequently Asked Questions

What's the difference between a cube and a cuboid?

That's a great question. A cube is a very special type of cuboid. On a cube, all six faces are perfect squares of the exact same size. A cuboid also has six faces, but they are rectangles, and they don't all have to be the same size, like a cereal box.

Do curvy shapes like a ball have any vertices?

No, they don't. A vertex is a sharp point where straight edges meet. A ball, or a sphere, is all curved and has no straight edges, so it can't have any vertices.

Is a corner the same as a vertex?

You are right that the vertex is the pointy corner of a shape. 'Vertex' is just the special maths word we use for it. When we talk about more than one, we say 'vertices'.