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As much as I would have liked to do another experiment with chocolate, I don't really have time to go buy a larger belt, so this week's experiment is related to fireworks instead. If you are in the USA, you are probably going to see fireworks for July 4th. Have you ever wondered how they get the different colors into the fireworks? If you want yellow fire, do you add yellow paint to the mixture? No, that would not work. To see how the colors get into fireworks, you will need:

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This week's experiment came from a shopping trip. I recently paid for my groceries with a $50 bill. Most stores test large bills with a special pen, to see if they are counterfeit, but this store had run out of the special pens. Instead, they put a drop of iodine on the bill to be sure that it was good. To see why, you will need:

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Use chemistry to change the colors in a bouquet of flowers.

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This spice makes a marvelous acid/base indicator!

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Why are candle flames yellow?

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What is Smoke?

We frequently see smoke, but what is it made of?

A fun but smelly test to find tannins in your food.

This project has Science Fair potential.

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This week, we are going on a hunt. No, we are not hunting for birds on wires, as I did for this week's video. Instead, we are hunting for acid. The word "acid" usually makes people think of dangerous chemicals, burning and corroding, but it describes an entire range of chemicals.

OK, so where are we going to look for acids? Not in your car, although there is acid in the car battery. Instead, we will look for acids in your refrigerator. The refrigerator! What would acid be doing in there? As we shall see, it is sitting there waiting for you to consume it.

Before we start hunting, we really should know what an acid is. A chemist will tell you that an acid is a chemical that will give up a hydrogen ion to another compound, called a base. That may seem complicated, but there is an easier way to identify acids. All we have to do is look at the word itself. Acid comes from acidus, the Latin word for sour. Acids have a sour taste.

Taste! Wait a minute! Don't try tasting battery acid, or for that matter, any chemical that is just lying around. We will limit our tasting to the things in your refrigerator, but don't worry. We will find plenty of acids there.

Now comes the fun part. Go open the refrigerator door, and we will start our hunt. Lets begin with the easy things. What do you see that has a sour taste?

If your refrigerator is like mine, the first thing you will see is a jar of pickles. Actually, in my refrigerator, you would see five or six jars of pickles, because I really like pickles. What do pickles taste like? Sour, right? Even sweet pickles have a sour taste, mixed with the sweet. Don't take my word for it. Have a pickle. What makes pickles taste sour? Vinegar, and most of the flavor of vinegar comes from acetic acid. As you taste your way though the refrigerator, you should find all sorts of things that contain vinegar, from salad dressings to hot sauces to mustards.

OK, now what else in here tastes sour? What about that lemon hiding down there on the bottom shelf? Lemons are certainly sour, which means they should contain acid, and they do. The acid in a lemon is citric acid, which makes sense since lemons are citrus fruit. Citric acid is found in other citrus fruits, such as limes, and grapefruits, but it is also a common ingredient in jams, jellies, canned fruit, and even soft drinks. While you are in the refrigerator, be sure to taste all those too.

We have found two abundant acids, but don't stop now. Those soft drinks contain another kind of acid called carbonic acid. Carbonic acid is formed when you dissolve carbon dioxide in water, so anything that is carbonated contains this acid.

The citrus fruits also contain ascorbic acid, also known as vitamin C. If you have ever taken vitamin C tables, you will remember the sour taste. Ascorbic acid is present in tomatoes and many other fruits and vegetables.

Looking on down the shelves, you might see a carton of sour cream. A quick taste will tell you that it lives up to its name, so it must contain acid, and it does. In this case, it contains lactic acid, an acid formed when milk spoils, which is why we say that the milk has soured. It is also the acid that gives yogurt it’s pleasantly tart flavor.

If you happen to have any strawberry rhubarb pie, the tartness of the rhubarb comes from oxalic acid, which is also present in spinach, beets, many kinds of berries, and even in chocolate.

If you continue tasting and reading labels you will come across several other acids, but by now you should realize how large a role acids play in the flavors of our food. Even that bowl of cherry ice cream that is waiting for me contains citric acid, ascorbic acid, and oxalic acid.

Do limit your tasting to the yummy stuff in the refrigerator (and the freezer where the ice cream is kept), but since practically everything in your refrigerator contains at least a little acid of some kind, you should have no trouble satisfying any sour cravings. Well, my ice cream is melting and the chocolate sauce is calling, so I will stop for now.

Have a wonder-filled week.

This week's experiment comes from an article I read on technological developments. While reading about ways to make iron, glass, and other historic processes, I became fascinated about the section on soap making. Now, we will not go through the entire process of making soap (at least not this week), but we will experiment with the first steps in classic soap making. To do that, you will need:

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How do they get all the different colors in fireworks?

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Can you mix two clear liquids to produce a black liquid? Of course you can!

Part 2 of this video is at: http://thehappyscientist.com/science-video/changing-colors-part-2

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A continuation of video 120 (http://thehappyscientist.com/science-video/changing-colors-part-1). This time we will mix two clear liquids to form a white liquid. Then we mix that with the black liquid from last time, to wind up with a clear liquid again.

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Make an easy indicator solution for identifying acids and bases.

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