The other kind of change that can take place when something is done to something is a chemical change. This involves actually changing the very material that the thing is made of, way down in the atoms of the thing where you can’t look, even with Dad’s binoculars. When two chemicals are mixed together in a laboratory beaker and everything explodes, the kind of change that has occurred is a chemical change. Unlike physical changes, chemical changes actually change stuff forever, or until Dad gets home and you have to throw it all away.
You will want to perform this experiment in your own kitchen to illustrate chemical changes. Fill a large bowl with baking soda. Then slowly pour white vinegar onto the baking soda. You will see the mixture froth and bubble up quite rapidly, accompanied by a hissing noise. This is because a chemical change is taking place: the baking soda is a “base’ and the vinegar is an “acid.” When an acid and a base are mixed up, they cause a chemical change in each other and a funny smell and, usually, a mess.
Even better than vinegar and baking soda is Drano and bleach. But do not mix them together – even in the toilet – because, oh my, do they ever go up. However, you might want to keep a supply of Drano and bleach and also vinegar and baking soda in the basement for whenever you feel scientific and wish to demonstrate the interesting properties of chemical changes.
Now try pouring a variety of different substances into the bowl and performing the same experiment. Notice how with many powders (such as cake mix, flour, sugar, salt, spices, cereals, talcum powder, foot powder, makeup, etc.) the result of mixing with vinegar is only a physical change: the stuff just sort of lies there in the bowl and gets wet. This shows you that certain things must have certain properties or be made of certain kinds of stuff in order to take part in chemical changes. You can even try putting the whole mess in the oven, the way Mother does with bread and dinner and such. Do not worry about being thought a “sissy” by your friends: there is nothing sissy about cooking, especially in science, where at any moment something may catch fire and fill the kitchen with smoke.
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