Space and Geometry: Two-DimensionalSpace

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Outcome
SGS2.2a Manipulates, compares, sketches and names two-dimensional shapes and describes their features.

SGS2.2b Identifies, compares and describes angles in practical situations.

Indicators:
  • Identifies and names pentagons, octagons, trapeziums and parallelograms.
  • Finds lines of symmetry for a given shape.
  • Identifies and names perpendicular lines
  • Identifies angles with two arms in practical situations e.g. corners
  • Identifies angles in two-dimensional shapes.
  • Describes the features of quadrilaterals.
  • Compares angles using an angle tester.

Lesson 1
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Two- Dimensional Objects
Introductory Activity

Pull out plastic 2D shapes out of a bag. Students need to write down the name of the shape they believe it is. When all the shapes have been pulled out, go through each shape calling out the name. Students need to check whether they wrote down the right name for the shape.
Revise the 2D shapes and Identify the properties of each shape, edges, corner etc (revise properties of shapes if needed). Complete one shape and identify its properties as a class.
Short Activity
Students complete worksheet of 2D shapes (this can be done in pairs).
(Worksheet 1)
Show students a picture of a quadrilateral shape. Pose questions such as:
  • What is a quadrilateral?
  • What do you know about quadrilaterals?
  • When is a shape not a quadrilateral?
  • Describe the sides of a quadrilateral.
  • Describe the angles of a quadrilateral.
  • Can a quadrilateral be an open shape?
  • Why do you think that?
  • If the orientation of a quadrilateral changes, can it become a non-quadrilateral? Why?
Organise the students into groups and provide each group with, scissors, rulers and pencils.
Have the groups cut out and sort examples of quadrilaterals and non quadrilaterals. (Worksheet 3) Ask each group to select from its collection some examples and non examples of quadrilaterals.
Have them paste them onto the concept chart. (worksheet 2)
As a class, discuss the placement of the shapes. Relocate any shapes that the class decides have been placed incorrectly.

Resources: Worksheet 1, Worksheet 2, Worksheet 3, 2D Shapes



Lesson 2
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Angles
Revise angles- What is an angle? Angles are formed when two lines meet. (A line connects two points and can go on forever in two directions)
Explain that we measure the size of an angle in degrees.
Revise right, acute and obtuse angles.


__Acute Angle__ (sharp)
an angle that is less than 90°
__Right Angle__
an angle that is 90° exactly
__Obtuse Angle__ (blunt)
an angle that is greater than 90° but less than 180°


On the board draw different acute, obtuse and right angles. Ask students if they can name these angles. (students record in their book)

Revise parts of an angle:
The corner point of an angle is called the vertex.
The two straight sides are called arms.
The angle is the amount of turn between each arm.

Activity
Angle tester:
Students work in pairs and make angle testers using geostrips. Ask students to use their testers to measure angles in the room. Students can then trace the angles into their books. Label the angles as either acute, right or obtuse angles.

Worksheet: find the angles in shapes
Resources: Geostrips, worksheet 4



Lesson 3
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Line of Symmetry

Introduction

Have the students sit with a partner and discuss the meaning of the word symmetry.
Ask several students to share their discussion with the whole class until a definition is agreed upon.
  • What is a line of symmetry?
  • How can you determine if a line is a line of symmetry?
  • Can a shape have more than one line of symmetry?
  • What examples can you give?
Teacher explains that an object has symmetry when it can be folded so that the two halves match or are identical. The fold line is called the line of symmetry (the shape needs to match when it is folded vertically, horizontally or diagonally). Shapes can have multiple lines of symmetry.

Teacher demonstrates by folding a 2d shape, i.e. a triangle. Teacher poses questions; does this triangle have a line of symmetry? etc.


Main Activity
Students are given large pictures of 2D shapes to cut out. In groups of three, students are to fold the shapes and find whether the shape has a line of symmetry and how many. Students will record their findings on a table they will draw up in their books (worksheet 5). Students can check with other groups to see if they received the same answer. If they have received a different answer students will re-check by folding the shape to see whether both halves are identical.

QUESTIONS:
Which shapes had the greatest number of lines of symmetry?
Which shape does not have a line of symmetry, why?
How many lines of symmetry does a square have? (Question other shapes).
What things around the classroom do you think are symmetrical?

Worksheet: If finished before time student’s complete worksheet on lines of symmetry (Worksheet 6 )

Resources: Large images of 2D shapes, Worksheet 5, Worksheet 6, Worksheet 7, 2D game, scissors.

Extra Activities/lessons
Parallel and Perpendicular Lines worksheet: worksheet 7
PARALLEL LINES
PARALLEL LINES IN THE ENVIRONMENT
Students seek examples of parallel lines from their environment, e.g. road markings, lines in exercise books, railway tracks. The exercise is repeated this time looking for parallel patterns, e.g. lattice work, brick work, patterns of windows in buildings. The different arrangements of the parallel patterns can be highlighted.
GAME:
What two-dimensional shape am I?
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