The Science Of Chalk!

What is chalk? Where does it come from? How does it work? Can we make our own? Ms. Carleen explains it all in The Science of Chalk on FB Live or you could watch on IGTV!

 

Calcium Carbonate vs. Calcium Sulfate

Supplies:

• Chalk – various varieties
• Bowls – enough for each variety of chalk
• White vinegar

Experiment:

1. Place each piece of your varieties of chalk into individual bowls
2. Cover each piece of chalk with the vinegar
3. Observe!
4. What happened to each piece of chalk?

But Why!?

Chalk is made from coccolithophores (dead sea creatures) and is very alkaline (that means on a pH scale they show up very high), but vinegar is an acid and has a very low number on a pH scale, making them science opposites. Because of this, they cause a chemical reaction that releases carbon dioxide gas, causing it to bubble and fizz. However, if the chalk is made from gypsum (a mineral), it will not do anything as it has a neutral pH, which is not high or low, so it doesn’t react to the acidic vinegar.

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Let’s Make Our Own Chalk!

Supplies:

• Plaster of Paris
• Water
• Paper cup
• Spoon
• Coloring for chalk
  • Try different types of color additives
    • Tempera paint
    • Food coloring
    • Powder colors
    • Use your imagination!

Experiment:

1. Add ¼ cup of plaster of paris to a paper cup (or more if you want a larger piece of chalk in the end). 
2. Add about ¾ of the amount of water, a little bit less if you are using a liquid coloring a little bit more if you are using a powdered color.
3. Mix in your coloring until you get your desired color. Try swirling different colors to see what you get!
4. Add your color in quickly, as the plaster dries quickly (depending on the amount of water added. Don’t worry if yours is a little watery at first, it will dry out and still work fine.)
5. Make more if you’d like and try different color additives and colors.
6. Let the chalk sit and dry overnight.
7. Tear off your cup to reveal your chalk.
8. Commence drawing on any surface you are allowed to draw on with chalk. Try the driveway!

But Why!?

Plaster of Paris is powdered gypsum, a mineral, therefore it is exactly what a lot of chalk is made of and is definitely more available to use than finding a few million dead coccolithophores at the bottom of the ocean! Another option would be to find and crush limestone to use as the base. Then you will have both kinds of chalk.