Circle Circus

Designed By:  Andress Carter-Sims, Virginia Pack Elementary
& Colette Dryden, Satchel Ford Elementary

1) Core Curriculum Objective:  Identify the center, radius, and diameter of a circle.  (3GS1-8)

Grade Level:  Three Subject:  Math

2) Overview:  Students will use a bubble solution and straws to create circles on their desks in order to find the center, and identify the diameter and radius of the circle (bubble).

3)  Focus Question:  How can we find the center of a circle?  What is the radius of a circle?  What is the diameter of a circle?

4) Time Frame:  Three 50 minute class periods

5) Resources/Materials:

Dishwashing liquid

Water

2-liter soda bottle for each group

straws

white paper

paper towels

transparency of a circle

overhead

laminated paper dots (punch holes in colorful laminated paper)

rulers

tag board circles of varying sizes

Bubble Solution Directions:  Place 3 teaspoons of dishwashing liquid (Dawn works well) into a two-liter soda bottle and fill the rest of the bottle with water.  Shake the bottle well to disperse the detergent throughout the solution.  Make a bottle of bubble solution for each group prior to lesson.  Solution works better if allowed to sit overnight.

6) Culminating Assessment:  Students will choose five circles of varying size.  They will trace each circle on white paper and label the center, radius and diameter.  The students will measure the radius and diameter and record each measurement next to the appropriate label.  They will then explain the relationship they see between the radii, and diameters.  The teacher will score the students’ work with the following rubric.

Rubric for Circle Circus  

7) Instructional Activities:

Activity One:  Students will choose partner.  The teacher will ask them to write their own definition of a circle on a plain piece of white paper.  Ask students to illustrate what they think a circle looks like.  Do not allow students to use a dictionary or any circular objects to complete this. 

Each group will be asked to share their definition and illustration of a circle.  The teacher will encourage the groups to explain how they felt drawing a circle freehand.  During this guided instruction the teacher will explain that every point on the circle must be the same distance from the center of the circle in order for it to be a circle.  Discuss what is meant by “center” of the circle.  Have the groups find the center of their illustrations.  The students will then use a ruler to measure several points on the circle to the center to see if their illustration is actually a circle by definition.  (Most of the students’ illustrations will NOT be circles by definition because they were drawn freehand.) 

Each small group will be given a bottle of bubble solution, paper towels, a laminated dot, and a straw.  The teacher will instruct them to use the bottle cap to measure the bubble solution.  Each student in the group will pour a capful of bubble solution into the cap and then pour that capful onto the center of their desk.

The students will then use the palm of their hand to produce a small amount of lather on the desk by moving their hand in a circular motion.  The student should then place one end of the straw in their mouth and the other end should touch the table where the bubble solution is located.  Students should blow very gently until a bubble begins to form on their desk.  Some practice may be needed.

Students will blow the bubble to an appropriate size.  Once the bubble pops, students will be able to see the size of the bubble from the lather print left around the popped bubble.

The teacher will place a transparency of a circle on the overhead and find the circle of it to model for students how to measure from the circle to the estimated center to find the center. The teacher should then label “center” on the transparency.

Students should then locate the center of their circle by placing the laminated dot in the middle and measuring in several spots to self-check.  The teacher will remind students of the definition of the circle and encourage them to use it to find the center.  Partners may help each other locate the center of their circles.

Next, the students will measure from the dot to any point on the circle in several different places like they did in order to find center.  The teacher will guide the discussion so students will know that what they have measured is called the radius.  Write the word on the overhead and measure.  Write the measurement next to the word “radius”.  Have the students do the same for their bubble circle.

If time allows, have students blow several more bubbles and find center and radius measurements for each.  They may work together to assist each other as the teacher monitors and assesses understanding by questioning.  What is the radius of that bubble?  How do you know?  Where is the center?  How do you know?

Activity Two:  The teacher will give the small groups a bottle of bubble solution and paper towels.  Each student will be given a laminated dot, ruler, and a new straw.  Ask the students to blow a bubble on their desk and find center and measure the radius of their circle again and record their information on a piece of paper. 

Using the same circle, they will be asked to measure from one point on the circle to the opposite point on the circle and again record the information.  The ruler helps the students keep the lines straight.

Once the students have recorded the data, the teacher should put a circle on the overhead, label the radius, measure the radius, and record the measurement.  The teacher should then measure from one side of the circle to the other side and record that information.  The teacher will lead a discussion so students will know that the measurement from one side of the circle to the other side is called the diameter.  The teacher will explain that the diameter is always a straight line from one side of the circle, through the center to the other side of the circle. 

Give students a copy of the chart below to guide their exploration.  Have them record the radius and diameter of several bubbles.  Have the students blow several bubbles.  Use paper towels to dry the desk in between bubbles.  Once all students have completed several bubbles and recorded the data, lead a discussion so the groups can share with the class what they have noticed about radius and diameter.

The teacher should then explain the relationship between radius and diameter.  FACTS TO INCLUDE:  If given the radius you can multiply by 2 to get the diameter.  If given the diameter you can divide by 2 to get the radius.  (Remember: Diameter = Division)

Ask the class to look at the chart on which they recorded their bubble circle data.  Compare radius and diameter.  Discuss the pattern and how they can use this in order to find radius when given diameter or diameter when given radius.

Activity Three:  Have each student choose 5 tag board circles of varying sizes, white paper, and a ruler.  Instruct students to remember what they have learned in the past few days in order to complete the task.  Tell them to first trace each circle.  They are to find and label the center, radius, and diameter of each circle.  Tell them to measure to find the radius and diameter of each circle.  After they have completed this, they are to write about what they learned about the relationship between the radius and diameter of a circle.  The teacher will use the rubric to score.  The students should choose whether to post the assessment on the school’s web page or on a bulletin board.