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AS ACID, ALKALI, OR NEUTRAL
How many kinds of liquids are there? How many ways can they be sorted? With our eyesight we can list the colors of different liquids. With our sense of touch, we can tell the consistency (pronounced "con-SISS-ten-see") of a liquid. With our sense of smell, we can test them for their odors. Unless liquids are moving (like a river or a faucet), we can't tell much about them with our sense of hearing. Much can be learned about liquids by tasting, but only if it is food. WE DO NOT TASTE WITHOUT PERMISSION.
After we have used our senses as much as we can, we have to use other ways to test and classify liquids.
All liquids fall into one of three categories having to do with what is called pH. That is to say that liquids are either neutral, like water, acid like citrus fruits and vinegar, or alkali (sometimes called "basic") like ammonia, lye (which is in soaps), or soda.
One way to test for pH is by using litmus (pronounced "LITT- muss") paper. It can be purchased at the drug store, at places where they sell swimming pool supplies, or at pet stores where they have aquarium supplies.
Blue litmus paper tests for acids, and it turns various shades of red when dipped into acidic liquid.
Red litmus paper tests for alkalis (bases). It turns various shades of blue when dipped into alkaline liquid.
Remember, we asked each of you to bring four liquids from home so that we can test them. You have lots of good stuff in little bottles and jars.
Make a heading on your paper by putting the word "ACID" on the top at the left, and the word "ALKALI" on the top to the right of the middle, so you can make two lists.
the lids, and do your testing, by dipping a small piece of blue litmus
paper into a jar, then writing the name of the liquid under the category
into which it belongs. If the blue litmus paper turns red, that means
your liquid is acid. If nothing happens, test it with the red litmus paper.
If it turns blue, write the name of your liquid in the
Surely you've noticed that some acids made the paper redder than others. The dark red means the acid in that liquid is stronger than that in the liquids that turned the blue paper a light color of red. Same with the paper used for testing alkalis--the dark blue is more alkali than the light blue. You can group your liquids again, in the same columns, but this time, putting the stronger ones first on the lists.
Now we'll have a little cooking lesson. Cream of tomato soup is fun to make, and a little science is necessary to make it properly.
Cook one can of whole or diced tomatoes in a large pot until it has boiled a few minutes. Add a little salt, and if you want, a small amount of minced onion.
Of course, to have "cream" of tomato soup, you need to put in some milk.
WAIT! STOP! If you put milk into the tomatoes, the milk will curdle, and be awful. Why do you think that is?
Tomato is acid. Milk is not. They can't be mixed just like that. What do we do, then, to make "cream" of tomato soup? Science has provided us with an answer to this problem.
Baking soda is alkali. Add one teaspoon of baking soda to the tomatoes. Watch it foam! Zowie! Something is happening here! After it cooks awhile, the foam will go away, and now, you can add the milk.
It will not curdle because you neutralized the acid in the tomatoes by adding baking soda. And the soup is lovely, besides!
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