Lesson Video: 2D and 3D Shapes Mathematics • First Year of Primary School

Video Transcript

2D and 3D Shapes

In this video, we’re going to learn how to describe shapes as two-dimensional or flat shapes or as three-dimensional or solid shapes. We can sort shapes into two types, those that are flat and those that are not flat. The better way of saying not flat is “solid”. This orange square is a flat shape. We could measure this side here, and we could measure this side here. But we can’t measure how high it comes off the page because it’s flat. It only has two dimensions. And so we can say a square is a 2D shape. Let’s put it in our flat shapes group.

Now, what are some other 2D shapes? A circle is a 2D shape. We know this because it’s flat. We could also include shapes like triangles and also rectangles. Squares, circles, triangles, and rectangles are all examples of 2D or flat shapes. But what if a shape is more like an object? It’s solid. We call these type of shapes 3D shapes; they have three dimensions. This cube has three dimensions. We could measure its length, its width, but also its height. And because it has height, it’s not flat. This is a solid shape.

You know, it’s hard to show solid shapes on a video like this. So a good thing to look for is if part of the shape has been shaded in, as if it’s in shadow. This means that the person who’s drawn it wants to show this is a solid shape. So a cube is a solid or 3D shape. What other shapes are 3D? A sphere is a solid shape. We can pick up a ball, and we can roll it. This cone is a solid shape. And we know cuboids like this brick are solid shapes. Bricks need to be 3D objects. Imagine trying to build a house out of a 2D shape. It would be flat. If you look around you as you’re watching this video, sure you’ll see lots and lots of solid 3D shapes. But if you look carefully, you’ll see some shapes that are flat, too.

How well do you think you can spot a 2D or a 3D shape? Let’s try some questions.

Which shape is flat?

In this question, we can see a picture of two shapes. And there’s a keyword in our question that we need to understand. We’re asked, which of the two shapes is flat? The blue shape has three sides. That’s how we know it’s a triangle. If we look carefully at our second shape, we can see that it has a curved surface that goes all the way around, a flat surface at one end, and a point at the other. That’s how we know the name of the shape is a cone. So our question’s asking us, which shape out of a triangle and a cone is flat? Well, we know that a cone is a solid shape. We know that ice cream cones and traffic cones are objects, whereas a triangle is a flat shape. It’s not a solid shape. Out of our two shapes, the shape that’s flat is the triangle.

Which of these shapes is 3D?

In this question, we’re shown pictures of two shapes. And they look very similar at first glance. But if we look more carefully, we can see that they’re actually different shapes. Our first shape is a pyramid. It has a flat base and several surfaces that go up to a point. It’s just like the pyramids that were built in ancient Egypt. And our second shape, we know, is a triangle. Our question asks us, which out of our two shapes, the pyramid or the triangle, is 3D? 3D is a short way of saying the words “three dimensional.” A shape with three dimensions has got length, width, but it’s also got height. A 3D shape is a solid shape, not a flat shape. It’s more of an object.

So out of our pyramid and triangle, which one is a solid shape, not a flat shape? We can see that the pyramid is a solid shape. A triangle is a flat shape. When we think of those huge pyramids in ancient Egypt, these are big objects. They’re not flat on the ground, they’re very, very tall. A pyramid is a 3D shape.

Which box does this cylinder go in?

This is a sorting question. We’re given a shape. It’s this blue cylinder here. And we’re given two possible boxes to sort it into. The first is labeled 2D, and the second is labeled 3D. Let’s remind ourselves what 2D and 3D shapes look like. 2D or two-dimensional shapes are flat shapes. And if we look in the first box, we can see several flat shapes. Rectangles, circles, and hexagons, you may not know the name of that one, are all examples of flat shapes. They’re 2D shapes. 3D or three-dimensional shapes are solid shapes. They’re not flat at all. Cubes, spheres, and cones are all solid shapes. These are actual objects that we could pick up.

So which of our two boxes does the cylinder belong in? Is it a flat shape or a solid shape? Well, a cylinder is a solid shape. There’s lots of ways that we know this. We could tell just by looking at the picture. We can see that this isn’t a flat shape. But also if we think about the types of everyday objects that are cylinders, things like cans of fizzy pop. We know that they’re not flat at all. Imagine trying to drink a flat can of fizzy pop; it’d be impossible. Our cylinder belongs with the other solid shapes. The correct box is the one containing 3D shapes.

So what have we learned in this video? We’ve learned how to describe shapes in two ways, as 2D or flat shapes or as 3D or solid shapes.