Chalk It Up

Challenge
A fun summer activity for all ages is using sidewalk chalk! Chalk and chalkboards have also taken off in forms of decoration in homes and in businesses.  Have you ever wondered how to make chalk? What ingredients do you think make chalk? Which kind of chalk is the best? Do different brands have different recipes? All these questions can be answered with this month's challenge. Your challenge is to follow different recipes to make chalk and determine which chalk is it best. You can also compare the different chalks made to existing chalk brands.

Your chalk making does have some criteria and constraints. You should follow the recipes given without altering them. The chalk should all be made the same size and same amounts. For tests of chalks, the same routine and test should be done as accurately and fairly as possible.

Materials

• plaster of paris
• tempera paint
• wax paper
• toilet paper tubes
• masking tape
• eggshells
• flour
• food coloring
• cornstarch
• water
• different brands of sidewalk chalk

Hints and Tips for Success

1. Allow students time to view the recipes at https://www.wikihow.com/Make-Homemade-Chalk and discuss which ones they believe will work the best.
2. Have students decide what molds they will be using and what fair tests will be done when the chalk is made (ability to write, ease of making, durability, etc.).
3. After discussing and figuring out fair tests, allow student groups to decide what chalk they will be making and how.
4. For differentiation, have the chalk already made, assign groups to make one kind of chalk for the entire class, have the fair tests provided or thought of for the students, only use different brands of store bought chalk. 
5. Allow students time to make their chalk and conduct the fair tests with it and the store bought chalk. Analyze results and discuss which chalk is the best and why.
6. Read the ingredients of the store bought chalk and see how it compares to the homemade pieces.