Mini-Lab 2: White Powders

Today we performed our second mini-lab that consisted of testing three white powders: cornstarch, baking soda, and baking powder; mixed together each one with iodine, vinegar and water. These white powders can not be determined when being compared with each other by just looking at them. They can only be determined through physical and chemical reactions when combined with other substances. We began by adding a few drops of water to these three powders and the only one with a noticeable reaction was the baking powder as it started to fizz but did not dissolve well.The baking soda did not fizz like the baking powder and turned clear to where you could see the particles on the bottom. The cornstarch became milky and had a cloudy quality but separated to where the milky water sat on top and the cornstarch sunk to the bottom. When iodine was added to the powders, the baking soda again began to fizz and turned a dark brown/black color; the cornstarch also turned a black color but did not fizz. When the iodine was added to the baking soda there was a dramatic change in appearance because it was not the black color the cornstarch and baking soda had been but was a yellow color! Finally, drops of vinegar were added to the cornstarch, baking soda and baking powder. The baking powder fizzed when the vinegar was added yet it did not dissolve. The corn starch had no chemical change such as fizzing but the solution was a milky color and it did not mix well. The baking soda and the vinegar got very fizzy when mixed and was also a milky white but had a easily distinguishable chemical change. Now when given unidentifiable powders you can distinguish which powder is which due to their physical and chemical reactions to iodine, vinegar and water. Chemical reactions is the change that produces something new (composition changed), it can be identified by having gas produced, color changed, or producing a precipitate from solution only. Physical reactions are changes in appearance but not a change in composition; this can be identified by its change of state, change of shape and change of size. Each powder is unique in its specific reactions to specific chemicals and other substances, which you can determine through a series of tests and experiments.



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