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Students identify and describe two-dimensional shapes like circles, squares, and triangles.
Look around your room right now. Did you know that everything you see—from your favorite book to the clock on the wall—is made of secret hidden shapes?
Every flat shape has special features that help us name it. We look at sides and corners. A side is a straight line that makes the edge of the shape. A corner (also called a vertex) is the pointy spot where two sides meet. Some shapes, like a circle, are special because they are perfectly round and have sides and corners. Other shapes use straight lines to close a space. When we count these parts, we can solve the mystery of what the shape is called!
Let's look at a triangle. 1. Count the straight lines on the outside: . It has sides. 2. Count the pointy spots where lines meet: . It has corners. 3. Any flat shape with sides and corners is a triangle!
Quick Check
How many corners does a circle have?
Answer
A circle has 0 corners because it is round.
What makes a square a square? It is the number of sides and corners! These are called defining attributes. A square must have sides that are all the same length and corners. Some things do not change the shape's name. These are non-defining attributes. For example, a square can be big or small. It can be red, green, or polka-dotted. Even if you turn it sideways, if it still has equal sides and corners, it is still a square!
Imagine you have two shapes: 1. A tiny blue shape with equal sides and corners. 2. A giant red shape with equal sides and corners. Even though they look different, both are squares because their sides and corners are the same!
Quick Check
If you paint a triangle bright purple, is it still a triangle?
Answer
Yes, because color does not change the number of sides or corners.
Squares and rectangles are like cousins. They both have sides and corners. However, a rectangle is special because it can have two long sides and two short sides. Think of a door or a piece of paper. If you take a square and stretch it out, it becomes a rectangle! To tell them apart, look closely at the side lengths. If all sides are exactly the same, it's a square. If only the opposite sides match, it's a rectangle.
Look at a standard envelope. 1. Count the sides: . 2. Count the corners: . 3. Look at the lengths: The top and bottom are long, but the left and right are short. 4. Because the sides are not all the same length, this is a rectangle!
Which shape has exactly sides and corners?
What happens to a square if you make it much larger?
A rectangle has sides and corners.
Review Tomorrow
In 24 hours, look at your dinner plate and your window. Can you tell someone how many sides and corners each one has?
Practice Activity
Go on a 'Shape Hunt' in your kitchen! Find two things that are circles and two things that are rectangles.