Solids Around Us (3-D Shapes) • Topic 1 of 4

Identification of Solids

Solids are the shapes that take up space. Where a square or a circle is flat and can be drawn on paper, a solid has three dimensions at once - length, breadth and height - so you can hold it in your hand. The chapter introduces five everyday solids, and the trick to identifying each is to picture a familiar object. A cube is a perfect box with six equal square faces, twelve equal edges and eight corners - think of a dice or a Rubik's Cube where every side is the same. A cuboid is the same family but stretched: six faces that are rectangles (with opposite faces matching), still twelve edges and eight corners - think of a brick, a matchbox or a textbook. A cylinder has two identical circular faces at top and bottom joined by one curved surface; it can stand and stack on its flat ends or roll on its side, like a cold-drink can or a candle. A cone has a single circular base and a curved surface that narrows to a sharp tip called the apex - an ice-cream cone or a birthday cap. A sphere is perfectly round all over, with one continuous curved surface and no flat parts at all, like a football or a marble. The fastest way to tell solids apart is to ask three quick questions: does it have flat faces, can it roll, and does it come to a point?

✅ Solved examples

1. Which solid has 6 equal square faces, 12 equal edges and 8 vertices, like a dice?
A cube. All six faces are identical squares, which is what makes a dice or a Rubik's Cube a cube rather than a cuboid.
2. A child holds an object that has two flat circular ends and one curved surface, and notices it can both stand upright and roll on its side. Name the solid.
A cylinder. The two flat circles let it stand and stack; the single curved surface lets it roll. A cold-drink can is the classic example.
3. Which solid is perfectly round, has only one curved surface, and has no edges or vertices at all?
A sphere. With no flat faces and no corners, a sphere (like a football or marble) can roll in every direction.
4. How is a cuboid different from a cube even though both have 6 faces, 12 edges and 8 vertices?
A cube has six equal square faces, while a cuboid has rectangular faces and its length, breadth and height are usually different. A brick is a cuboid; a sugar cube is a cube.

✏️ Practice — try these, take hints as needed

1. Which solid tapers from a flat circular base to a single sharp point called the apex?
Think of an ice-cream holder or a birthday cap.
It has one flat face and one curved face.
It has exactly one vertex.
Cone
2. A matchbox and a textbook are everyday examples of which solid?
Six faces, but they are rectangles, not squares.
Length, breadth and height are different.
Cuboid
3. Name the solid that has two identical flat circular faces joined by a curved surface.
It can stand on its end and roll on its side.
A gas cylinder or a candle is an example.
Cylinder
4. What single feature most clearly separates a sphere from a cylinder and a cone?
Look for flat faces.
A sphere has none of one particular feature that the other two have.
A sphere has no flat face at all (only one curved surface), whereas a cylinder and a cone each have at least one flat circular face

📝 Topic test — 8 questions

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