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Activity

Modeling Clay

Summary: 
Baking soda and cornstarch make a smooth, pliable white clay when cooked together.
Science content (2016 curriculum): 
Chemistry: States of Matter, Properties of Materials (K-7)
Chemistry: Physical Changes, Solutions, Mixtures and Separating (2, 4, 5, 6)
Materials: 

2 cups baking soda
1 cup cornstarch
1.5 cups cold water - I would try reducing to 1.25 cups to make a less
sticky clay

For a class of 22 students, with half pound each of clay, and 5 portions left over, I used 2 boxes of cornstarch (each 454g) and nearly 4 boxes of baking soda (each 1kg). There was about 3.5 cups in each box, so the total was about 7 times the recipe, cooked in two batches in a large pasta pan.

Procedure: 

Put all ingredients in a cookpot and stir until smooth.
Cook over a medium heat and stir until boiling.
Keep stiring and heating gently until it is the consistency of mashed potatoes.
Turn out onto a plate and cover with a damp, well-wrung kitchen towel to let cool.
Once cool knead until pliable.

The clay can be coloured with food colouring, or left white and
painted once it hardens.

When you have made your model, leave it to air dry - turning over every 12 hours or so.
It might take a few days to fully dry.

Grades taught: 
Gr 1
Gr 2
Teaching site: 
General Gordon Elementary