Basic Chemistry

This year, Casia is studying Biology for science. We started with the scientific process, then she learned about evolution, followed by taxonomy. But before we could dive into cells and cell structure, Casia needed to learn some chemistry. 

Casia was familiar with the terms atom and molecule, but she really didn't have a good understanding of them. So we started there. She learned about the components of an atom, what elements are, what the periodic table is, and how molecules are formed. She learned about the three dimensional nature of molecules and how they interact with each other in chemical reactions. 

We followed this week long lesson up with a really fun lab I found on the website for The National Science Center. They entitled it "Mystery Powder". It's essentially a qualitative analysis (always one of my favorite types of chemistry labs!) with baking ingredients. It was really easy to set up and clean up and Casia had a blast!

To start, we gathered all necessary ingredients:

• baking powder 
• baking soda
• cornstarch
• cream of tartar
• tincture of iodine
• vinegar
• red cabbage juice
• two copies of the chart (off the National Science Center website)
• pencil
• permanent marker
• measuring spoons
• wax paper
• medicine droppers
• nine cups.

After gathering all the supplies, Casia was able to follow the step-by-step instructions with little help from me, which was good, because I was trying to take pictures of the process.

To set up the experiment, Casia labeled the disposable cups with each of the following: baking soda, baking powder, cornstarch, cream of tartar and mystery powder. She filled all but the the mystery powder with a teaspoon of the appropriate substance. She then left the room and I selected one of the substances and placed a teaspoon of it in the mystery powder cup.

Before we started with the actual experiment, I saw Casia examining the the mystery powder, trying to see if she could identify it right away. Part of me wanted to discourage this because it would make the lab less fun and interesting. The other part of me wanted to encourage her to explore. The latter part won and she began to eliminate 'suspects' right away. She said that the mystery powder had a very different texture than the baking soda. She described the baking soda as looking like salt, while all the others all looked like flour. She also said that the cream of tartar rolled into clumps unlike the baking powder, cornstarch and mystery powder, but the cornstarch clumped differently. So based on a visual inspection, she made her guess that the mystery powder was baking powder. I refused to validate (I wanted to keep the suspense going!)

She then went on to smell and taste each sample. For smell, the mystery powder was most like baking powder, and a little like cream of tartar, even less like baking soda and nothing like cornstarch. She stated that the baking powder and mystery powder tasted exactly the same. She mentioned also that it tasted slightly like baking soda and then a bit less like cream of tartar, but nothing like cornstarch (and then she asked if she could eat more of the cornstarch!) I still refused to confirm or deny her suspicions that the mystery powder was baking powder, so we moved on with the experiment.

She then taped her testing chart on a plastic place-mat and taped a piece of wax paper over the top of it. 

Next, she scooped 1/8 teaspoon of each substance, for each of their four boxes in their own column. She ended up with four little piles of each substance.

Casia then started with the water, dropping a few drops onto each pile of each substance in the water row. Then she watched what happened. I had her record her observations on her observation chart.

The mystery powder started to bubble (just like the baking powder) when she dropped water onto it.

Next, she dropped a few drops of vinegar on each substance. On the baking powder and mystery powder she noticed a small amount of fizzing, but with the baking soda, she got a BIG fizz. Casia said she had expected that because she has seen many 'volcanoes' at science fairs with baking soda and vinegar.

The third row was for Iodine. The baking soda and cream of tartar turned an orange color. The cornstarch, baking powder and mystery powder turned a purple-black color (indicating the presence of a starch).

Casia was very interested in the changed consistency of the substances, so I gave her some Q-tips to play with them.

I had prepared the red cabbage juice earlier that morning, but in retrospect, should have left it for her to make. It was very easy: I filled a large measuring cup with one red cabbage leaf, torn into little bits, then added two cups of boiling water. It was ready after about 10 minutes, maybe less (I wasn't really paying that much attention to it since I was also making breakfast.)

In the last row, she added a few drops of red cabbage juice to each substance. The baking soda turned blue (base), cornstarch turned purple (neutral), cream of tartar turned pink (acid) and the baking soda and mystery powder fizzed and turned a very pale blue. 

In the end, Casia correctly identified the mystery powder as baking powder. 

Although we talked to some extent about the chemistry going on in this experiment, I delayed explaining to Casia that baking powder is actually a mixture of baking soda, cream of tartar and some cornstarch, because the very next day we conducted another experiment.... "Find the Fizz" by The National Science Center (determine the mystery ingredient in baking powder).