Symmetrical Designs with Pretzels and Marshmallows

Designed by: Ashley Norton, Rosewood Elementary

Grade Level: 4    Subject:  Geometry

1) Objective: Create designs which have one or more lines of symmetry.  (4GS3-2 )

2) Overview:  The teacher will use inch graph paper and the overhead projector to demonstrate how to draw a symmetrical design. Toothpicks will be used to represent lines of symmetry in the design.  The students will work in groups of four using graph paper, rulers, and toothpicks to each plan their own design and lines of symmetry.  Using straight pretzels and mini marshmallows, the teacher will demonstrate how to turn the drawing into a two-dimensional design.  Students will then  take their plans and will create a two-dimensional design using straight pretzels and mini marshmallows. Toothpicks will be used to represent lines of symmetry.  Students will be assessed according to a rubric provided at the beginning of the lesson. 

NOTE: This lesson is designed to follow curriculum strand 4-GS3-1, identify and/or draw lines of symmetry in a given object or representation.

3) Focus Question:  How can you plan and create a design that has one or more lines of symmetry?

4) Resources:

At least 5 sheets of  inch graph paper per student (Template provided at the end of the lesson)

Overhead projector

Overhead pen

Overhead inch graph paper (Copy the paper at the end of the lesson onto a transparency.)

Pencils

Clear tape

Ruler for each student

Bag of straight pretzels for each group of four

Bag of mini marshmallows for each group of four

Box of toothpicks divided between the groups

Napkins for each group to catch the crumbs

Copies of culminating assessment for each student

5) Culminating Assessment:

The students will work in groups to each create a design with one or more lines of symmetry.  Students are encouraged to assist each other in planning and constructing their design.  Students will be assessed according to the following rubric.

Comments:

6) Instructional Activities:

Time Frame:  This lesson should take two 45 minute class periods.

Lesson One:

The teacher will hand out the culminating assessment, a ruler, and several sheets of graph paper  to each student.  The teacher should explain the culminating assessment to the students.  Students will be divided into groups of four according to ability levels.  The teacher will use the overhead projector, overhead transparency of the inch graph paper, and an overhead pen to demonstrate the assignment.

The teacher should go over the definition of symmetry and may need to provide an example of symmetry to remind students what symmetry is.  For example, the butterfly drawing that accompanies curriculum strand 4-GS3-1 would be a good illustration of symmetry.  The teacher should explain that they are to create a design using these materials that has at least one line of symmetry.  Tell them that whatever they draw must be made using straight pretzels and marshmallows later on in the lesson.  Circles are outlawed in this lesson because only straight lines must be used.  The teacher should start by drawing a square in the center of the overhead  graph paper using the overhead pen.  Then, the teacher should ask students if they can  think of a way to add to this drawing so the shape will be symmetrical. Tell students that one way to be sure that the figure is symmetrical is if you draw something on one side of the design, be sure to draw an identical pattern on the other side.  For example, if a student says to draw a triangle on the right side of the square, the student should understand that they should draw a triangle on the left side of the square.  The line of symmetry would be a line drawn vertically through the center of the square.  Represent this line by placing a toothpick vertically in the center of the square and fold the graph paper to demonstrate how the design is identical on both sides. Fold the paper horizontally to demonstrate that the object is also symmetrical horizontally as well.  Place a toothpick horizontally through the center of the square to show the second line of symmetry. Make sure that the students understand how to find the line of symmetry in their design.  Have the students practice creating a design  on their graph paper,  placing a toothpick in the correct place to show the line of symmetry.  The teacher should walk around to check the students designs and lines of symmetry.  The teacher may need to reteach with a small group if needed. 

The students are now ready to draw their design. Students should be encouraged to be creative but to remember that they have to be able to create their designs using pretzels and marshmallows.  Extra sheets of graph paper should be available if needed by the students.  They are sitting in groups of four to brainstorm ideas, check each others work, and provide suggestions if needed.  Each student is responsible for planning their own design and, in lesson two, making their design using pretzels and marshmallows.  The teacher should be walking around the room to assist students with this assignment.  Once the design has been planned, students should use toothpicks to show the line of symmetry.  They may tape them into place, if desired.  Students should complete their design and work with group members to be sure it meets the grading criteria before building it.

Lesson Two:

The teacher should review from Lesson One using the example design created as a class (the square with two triangles as the example in this lesson).  The teacher should place toothpicks, napkins and the bags of marshmallows and pretzels on each groups table.  The teacher should demonstrate how to take the plan created on the graph paper and make it using these materials.  The students should be using their materials on their table to create the example design along with the teacher. The teacher is going to explain that the straight lines are represented by the pretzel sticks and the marshmallows are like the glue to hold the pieces together.  The teacher will take a pretzel stick and stick a marshmallow onto the tip of the pretzel. (Remember that the students are creating this along with you on their napkin!)   The teacher will take a second pretzel and stick it into the marshmallow to create the letter "L."  Then, the teacher will stick a marshmallow into the tip of the pretzel and continue adding pretzels and marshmallows until a square is formed.  Then, the teacher will add marshmallows and pretzels to each side in a "V" shape, connecting the square and the triangle together.  The students and the teacher should have identical designs and should understand that the design was completed according to the plan.  Group members and the teacher should assist any students having trouble completing this task.  Next, the students should use the toothpicks to show the lines of symmetry as discussed in Lesson One.  One toothpick should be placed horizontally and one vertically through the center of the square.  (Toothpicks may need to be taped together if a longer line of symmetry is needed.)

Once the students have completed this step, they should begin constructing their own designs on a napkin. Using the marshmallows and pretzels on their tables, the students should construct their design according to their plan.  The teacher and the other group members should assist with this process as needed.  Toothpicks should be placed on the design to show lines of symmetry and taped into place.  Once the design has been constructed, the group members should check each others work to make sure it meets the grading criteria.  Any extra pretzels and marshmallows may be eaten at the end of the lesson or if the teacher chooses, some may be taken out and given to the students to eat during the construction of their design.  The plan, culminating assessment, and the constructed design with lines of symmetry  should be placed on a table in the classroom  to be assessed or the teacher may choose to assess it at the students table.