Thursday, January 19, 2012

Acid or Base


We finally got our hands on some Borax, so we were able to use the testing strips we bought a little while ago.  Noor measured out a bunch of different household substances:

Coffee
Tea leaves
Salt
Baking powder
Baking Soda
Citric Acid (instant lemonade)
Glucose
Borax
Flour
Rice
Sugar

First, she used her senses to make notes about the different substances: how did each one smell, feel, taste (not the borax), look?

Did any look like crystals with the naked eye?

Which ones had crystalline structures under the microscope?


Next, she mixed solutions with each substance to see which ones were water soluble.



And then, she tested each one to see where it fell on the scale of acids and bases:

Citric acid was the most acidic (red strip); our tap water was more acidic than neutral (yellow strip):

Borax was the most alkali:

Next, she explored which substances were reactive.  Citric acid, baking soda and baking powder (which is a combination of baking powder and baking soda) caused fizzing while the other substances did not:


And finally, Noor experimented with how heat changes a substance.  Glucose, when heated, becomes liquid and then caramelizes into a hard solid:


Flour burns but remains solid while salt doesn't burn at the temperatures we were working with.







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