Raven reads the side of the baking powder can. "It is not one substance," she says. "It is a mixture of three."
Rocket drips a little plain water into a spoonful of baking powder. It fizzes!
"No vinegar this time," he says. "So what is reacting?"
Nova lists three ingredients in glowing letters: baking soda, cream of tartar and cornstarch. "Would you like a hint?" she asks. "Only two of them react."
Raven smiles. "Then we test them in pairs," she says.
Baking powder is a mixture of three ingredients: baking soda, cream of tartar and cornstarch.
Cream of tartar is a dry acid. Dry, it just sits next to the baking soda.
When water is added, the cream of tartar reacts with the baking soda. The reaction makes carbon dioxide gas.
The cornstarch does not make the gas.
| Pair tested with water | Bubbles? |
|---|---|
| Baking soda and cream of tartar | Yes |
| Baking soda and cornstarch | No |
| Cream of tartar and cornstarch | No |
Raven tested the three ingredients two at a time.
Only the pair with baking soda and cream of tartar bubbled.
Testing in pairs is a smart way to find which parts of a mixture react.
| Statement | True or false? |
|---|---|
| Baking powder is a mixture of three ingredients. | ? |
| Cornstarch makes the gas in baking powder. | ? |
| Cream of tartar is a dry acid. | ? |
| Dry baking powder fizzes in the can. | ? |
You solved a mixture mystery with evidence. Tomorrow we will look for reactions in everyday life.