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3D Objects: Prisms, Pyramids & Spheres

Maths · Y3 Shape
Year 3
Lesson Guide
Explanation
A square drawn on paper is flat — 2D. But a dice you can pick up and roll is SOLID — 3D. Three-dimensional objects take up space: they have height, width AND depth. Everything you can hold is 3D: balls, boxes, cans, ice-cream cones. The flat shapes from last lesson become the FACES of these solid objects.
Your Turn
Pick up any box. Can you find the flat 2D shapes hiding on its surfaces? A cereal box hides 6 rectangles!
Watch Out
A picture OF a cube is still a 2D picture — the real 3D cube is the one you can hold.
Explanation
3D objects have their own counting words. A FACE is a flat surface (the part you could paint one colour). An EDGE is the line where two faces meet. A VERTEX is a corner point (plural: vertices). A cube has 6 faces, 12 edges and 8 vertices — grab a dice and count them for yourself!
Your Turn
Hold a box and count: faces (6?), then run your finger along the edges (12?), then touch each corner (8?).
Watch Out
Count carefully — the faces you can't see still count! Turn the object as you go.
Explanation
A PRISM is a 3D object that's the same shape all the way through — like a loaf of bread where every slice matches. The two matching ends name it: triangle ends make a triangular prism (a tent!), rectangle ends make a rectangular prism (a cereal box). A cube is a special rectangular prism with all-square faces.
Your Turn
Is a Toblerone box a prism? What kind? Check: yes — triangle ends, so a triangular prism!
Watch Out
Every slice must MATCH. An egg is not a prism — slices near the middle are bigger than near the ends.
Explanation
A PYRAMID has a flat base and triangle walls that all lean in to meet at ONE point on top (the apex). The base gives it its name: the famous Egyptian pyramids have square bases — square pyramids. A triangle base makes a triangular pyramid. Prisms go straight through; pyramids come to a point — that's the big difference.
Your Turn
Prism or pyramid? A tent with triangle ends; an Egyptian monument; a cereal box. Check: prism, pyramid, prism.
Watch Out
A pyramid's SIDE walls are always triangles — only its base can be a different shape.
Explanation
Some 3D objects trade flat faces for curves. A SPHERE (ball) is round every way — no faces, no edges, rolls anywhere. A CYLINDER (can) has two circle faces and rolls in one direction. A CONE (ice-cream cone, party hat) has one circle and a point, and rolls in circles! Now go hunting: your home is full of prisms, pyramids, spheres, cylinders and cones. Quiz and exercises!
Your Turn
Find one of each at home: a sphere, a cylinder, a rectangular prism. (Ball, can, cereal box…)
Watch Out
Name the OBJECT, not its face: a can is a cylinder, even though its ends are circles.
Step 1: Introduction
Step 1 of 5
2D is flat — 3D is solid square (2D — flat) cube (3D — solid) 2D shapes live on paper. 3D objects take up space — you can HOLD them. A drawing of a square is 2D; a dice you can roll is 3D.
The 3D counting words vertex (corner) edge face FACE = flat surface · EDGE = where 2 faces meet · VERTEX = corner point A cube: 6 faces, 12 edges, 8 vertices. Count them on a dice!
A prism is like sliced bread triangular prism (tent!) rectangular prism (box!) Slice a prism anywhere along its length — every slice is the SAME shape. The end shape names it: triangle ends → triangular prism.
Pyramids come to a point apex — the point on top square pyramid (like Egypt!) A pyramid has a flat BASE and triangle walls meeting at one point. The base names it: square base → square pyramid.
The round family sphere ⚽ no faces, no edges! cylinder 🥫 2 circle faces cone 🍦 1 circle + a point Spheres roll every way; cylinders roll one way; cones roll in circles! Hunt at home: ball, can, party hat, dice, tissue box, Toblerone…
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