Sample Lab Writeup
eighth grade

D.S.
8th
11/21/00
assignment #18

During science class, we had 3 mysterious powders that needed identity. We alredy knew that they were cornstarch, iodine, and powdered sugar, but we didn't know which was which. Since I bake sometimes, I had a basic idea of which powder was which; baking powder was clumpy and white, cornstarch is yellower than powdered sugar. To find the real identity, we decided to do an experiment.

We got a tray with 10 little holes in it. In 3 holes, we put cornstarch, in 3 powdered sugar, and in 3 more, baking powder. Since we didn't know the identity, we named the powders A, B, and C. To find the identity, we decided to mix each of the substances individually with iodine, water, and vinegar to see how each powder would react.

I expected the baking powder to react with the vinegar and iodine, but not the water. I thought the sugar and cornstarch would activate a little to iodine, but not vinegar and especially not water. By looking at this, I figured that is how I'd know which substances were which.

After we had mixed A, B, and C with the iodine, vinegar, and water, I could identify the substances. Substance A was baking powder. When mixed with water, it got creamy and turned whiter. The reaction to the vinegar was that it got foamy, it bubbled, and it fizzed. With iodine, it absorbed the iodine completely and got mushy. The cornstarch reacted mostly the same with water and iodine; it turned yellow and got more liquidy. With the vinegar, it turned yellow, foamy, and expanded. When water was added to powdered sugar, it got a frosting-like consistency. After a couple of minutes, it got really hard. When added to vinegar, it got milky and turned light yellow. When iodine was added, it got chunky and turned a creamy color. It looked like spoiled milk.

I conclude that substance A is baking powder, B is powdered sugar, and C is cornstarch. I could tell by A's reaction with vinegar that it was baking soda, and I knew that cornstarch would not be very reactive with vinegar. Powdered sugar isn't very active, so I know that vinegar wouldn't affect it much. With water and iodine, there was not much reaction.

Some things that could have affected this would be the age of the baking powder, age of the vinegar, and the amounts used of each substance. I know from baking experience that baking powder is less reactive when it is older. If it was old, it would've only fizzed a little. It was young, though, because it fizzed a lot. The opposite with vinegar. It it's older, it's stronger, just like wine. With the amounts of each substance used, if you have for example, a cup of vinegar and a tablespoon of baking powder, it's most likely going to be less reactive.

Overall, I think that powdered sugar and the cornstarch have no real "power" that caused them to react to anything. Baking powder has that strength in it that can cause things to bake, sometimes rise, in the oven. The same for yeast and baking soda. I think It'd be neat to do this experiment with yeast and baking soda. I know yeast doesn't chemically change in water, but I know water affects it. That's a completely different experiment, though!