Secret Ingredient Revealed

As a follow-up to Casia's previous experiment in Basic Chemistry, we did another activity from the National Science Center, Find the Fizz. This time, I let Casia make the red cabbage juice (pH indicator).

Casia tore one red cabbage leaf into small pieces and
placed them into a large measuring cup.

She added a cup of boiling water.

Then she tasted it. Unsurprisingly, it tasted like cabbage.

After a couple of minutes it changed to a blueish-purplish color.

The purpose of this lab is for the student to identify the ingredient, in addition to baking soda, that makes up baking powder. This lab builds on the previous one where various common baking ingredients were combined with water, vinegar, red cabbage juice and iodine and reactions were observed and recorded.

To begin, Casia placed 1/8 tsp. of flour, cornstarch and cream of tartar into their own labeled cups. She added 2 tsp. of water in each cup and stirred. Then she labeled 4 cups with the following: vinegar, flour, cornstarch and cream of tartar. She then poured 1 tsp. of the previously prepared red cabbage juice into each cup. Next, she used an eye dropper to place a few drops of the vinegar into the cup labeled vinegar; a few drops of the flour solution into the flour cup; and so on for the cornstarch and cream of tartar. 

The vinegar turned pink indicating an acid.

Cream of tartar was the only other ingredient that turned pink. 

Casia learned from the previous lab that when she added water to baking soda, no reaction was observed. But when she added vinegar to baking soda, it fizzed, releasing carbon dioxide. When she added water to baking powder, however, she also observed fizzing. Since cream of tartar was the only solution to turn pink like the vinegar, she concluded that the other ingredient in baking powder is cream of tartar. When the baking soda (the base) and cream of tartar (the acid) are added to water, a reaction occurs releasing carbon dioxide. 

I also explained to her that there is sometimes cornstarch added in as well, as a filler, which is why in the previous lab she found the baking powder reacted with the iodine- because there was some cornstarch in it as well. 

As a finish up to the lab, Casia took a sip of the vinegar. She been at this since she was about four years old, sneaking sips of the Easter egg dye because she loves the taste of vinegar!