If you have read many of these experiments, you know that I like experiments that deal with food. Part of this is because I really like to eat. I also like to cook, finding it very relaxing. I also seem to get lots of good feedback from the food related experiments, telling me that many of you like to eat too. This experiment comes from the wonderful dinner we had tonight. Our good friends Bob and James came by today and we went out to eat. I ordered a bucket of steamed oysters (I LOVE oysters!) and I was enjoying dipping them in the various combinations of horseradish, cocktail sauce, and butter. I especially like the clarified butter you get with seafood and that got me thinking about the chemistry butter. To investigate this, you will need:

• at least a couple of tablespoons of butter (not margarine)
• a skillet or sauce pan

Lets start with the history of butter. Butter has been used for a long time. There are references to butter as far back as 2000 BC, although at that time it was used mostly as a medicinal ointment and as oil for lamps. Today, most butter is made from cow's milk, but it has also been made from the milk of goats, sheep, horses and other mammals. There are different ways to make butter, but basically you let whole milk separate so that the cream comes to the top. This cream is then churned or shaken, causing the bits of butterfat in the milk to stick together, forming lumps of butter.

If you want to try that yourself, check out the Making Butter video.

Butter is actually several different substances mixed together. We are going to separate these substances. Cut a couple of tablespoons of butter into small pieces and put them in the pan. Turn the heat on low and watch as the butter melts. You will quickly notice that there are different parts to the butter.

Clear butter fat and white milk proteins

You will see a clear, yellow liquid with lots of white bits floating in it. Continue heating and you will notice that the butter begins to sizzle. At this point, remove it from the heat.

There will be a white foam floating on top of the butter and bits of white, solid stuff will settle to the bottom. In the middle is the yellow liquid. Use a spoon to remove the white foam. You can then carefully pour the yellow liquid into a small container.

boiling the water

Another way to make clarified butter is to place the butter in a small container and place it in a very warm place. The butter will melt and separate into layers. You can then spoon off the foam from the top and carefully pour off the clear, yellow liquid. You don't get the sizzle, so you miss seeing evidence of one of the substances present in the butter, but you also don't need to use the stove.

OK, now what is all this stuff? Well, butter is made up of fat, protein, and water. They form an emulsion, which means that you have a mixture of substances that usually don't mix (oil and water).

Some of the proteins brown,
giving the butter fat a wonderful flavor.

Often, butter has salt and air added to it as well. As you melted the butter, the emulsion separates. The yellow liquid is the fat. The solid, white stuff is the milk proteins. The sizzle of the heated butter was the water boiling away. The foam which forms on top of the butter is mostly due to air that is trapped in the butter during processing.

You can use either salted or unsalted butter in this experiment. If you use salted butter, you need to watch it more closely to keep it from scorching. The salt raises the boiling point of the water in the butter, which means less time between when the water starts to boil and when the proteins begin to burn.

Why do people make clarified butter, which is also known as drawn butter? There are several reasons. First, by removing the solid milk proteins, you can use the butter to cook at much higher temperatures. Regular butter begins to smoke when you heat it to about 248 degrees Fahrenheit. At that point, the proteins begin to scorch, producing a bitter flavor. By removing these proteins, you can heat the clarified butter up to 375 degrees before it starts to smoke. This makes it very useful for cooking food which you want to cook at a high temperature.

The second reason for removing the milk proteins is that it helps keep the butter from spoiling. These proteins are largely responsible for the butter going rancid as it gets old, and properly clarified butter can be kept for a long time without going bad. The better job you do of removing these proteins, the longer the butter will keep.

Now, I can hear some of you asking why isn't all butter clarified. Removing the milk proteins also removes a lot of the flavor. Once it cools, compare the taste of the clarified butter with regular butter and you should taste a big difference. While it tastes marvelous with oysters, lobster and other seafood, it would not have the butter flavor that we like in other foods. Don't waste that clarified butter! If you don't have any oysters or lobster laying around, it is also very good on popcorn. Or heat it again with some garlic, and use it for dipping crispy strips of toasted bread. YUM!

A classic investigation into the chemistry of bones.

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This activity is from my Experiment of the Week Newsletter. It is free, and will let you know about new resources on this site.

This time, we are going to take a look at a classic science experiment that has been used for a LONG time. In fact, it was already an old classic when I was a kid, and that was quite a while ago.

The experiment involves the link between our senses of taste and smell. Often it is done with apples and potatoes, but there is enough textural difference that you can often tell which is which. I have found that the results are much stronger with flavored candy. To try this, you will need:

• candy that has the same shape and texture, but comes in different flavors.

OK, lets begin with the standard experiment. Be sure that your pieces of candy will all feel the same in your mouth, and that they have distinctive flavors. If you don't see the candy, the taste should be your only clue to what flavor it is.

If you have a friend to help, then close your eyes, hold your nose, and have her give you one of the pieces of candy. Keeping eyes and nose tightly closed, put the candy in your mouth. You will taste a sweet taste, and probably some sour too, but you may be surprised that you can't tell if the candy is cherry, lime, orange, or some other flavor.

Then move your hand away from your nose, so you can breath normally. Yum! You get a sudden burst of flavor, telling you exactly what kind of candy it is. The reason for this is that your tongue has flavor receptors for basic flavors, such as sweet, salty, sour, bitter, and umami (the savory taste of meat.) Most of the other flavors that you taste are tied in with your sense of smell. If you can't smell them, then you don't taste them. That is why food tastes so bland when you have a cold.

But wait a minute! Your parents probably taught you to chew with your mouth closed. How can the smell get out of your mouth to go up your nose, so you can smell it? And your mouth stayed closed when you released your nose, but you still got that sudden burst of flavor. What is really happening?

Well, the smell of the food does have to reach your nose for you to taste all of those subtle flavors, but there is another path that those smells can take. Instead of inhaling those smells through your nose, you are exhaling them. As you breath out through your nose, your breath carries the smells from your mouth into your nose. You were not holding your nose to prevent you from inhaling the smells. Instead, you were blocking the way, so you could not exhale the smells through your nose.

Now that you are tasting the flavor, hold your nose again. After a second or two, the flavor disappears again.

So what if you just held your breath instead of holding your nose? Try that.

No, really. Try it and see for your self.

What did you find? Even holding your breath, you probably still tasted some of the flavor. Why? Think about what happens when you chew or swallow. Your mouth changes shape, your throat moves, your tongue moves around. All of that movement causes the air in your throat to move, forcing some of it up into your nose. It carries some of the smell to your nose even if you don't exhale. By blocking your nose, you pressurize it, preventing the air from your mouth from moving up.

OK, take it one more step. Hold your nose until the flavor goes away. Then release your nose, and inhale. While you are inhaling, keep your mouth closed. You probably won't taste the flavor. Then exhale. Ahh, there is the flavor again. The main path that the smells take to let you taste your food is up through the back of your throat. It is not inhaling that brings you the flavor. Exhaling is what gives you those wonderful flavors.

Way back in the 70's, when I was working at the Memphis Pink Palace Museum, part of our Kitchen Chemistry program involved using packets of ketchup to remove the tarnish from pennies. You take a dull, brown, tarnished penny and rub it with some ketchup. In seconds, the penny is bright and shiny. Usually, the experiment stops there, but I thought we might take a look to see why it works. To try this, you will need:

• ketchup
• water
• vinegar
• salt
• potassium chloride (salt substitute)
• 5 small cups or bowls
• 6 or more tarnished pennies
• labels and a marker

Safety Warning

Before you go wild with pouring different chemicals together, remember to keep safety in mind. For the stuff in your refrigerator and spice cabinet, you can pretty much mix whatever you want. Tuna fish and grape jelly may not be tasty, but it will not explode or burn off your fingers. Outside your refrigerator, you need to be much more careful. Cleaning supplies and other household chemicals can be harmful by themselves, and if the wrong ones are mixed they can be deadly. Only use them for experiments that specifically call for them.

Experiment

A good place to start is with the original experiment. Put a little ketchup onto one of the tarnished pennies. Let is sit there for about 30 seconds, and then rinse it. What you should find is that the tarnish has been removed from the part of the penny that was in the ketchup. OK, so that works just as well as it did back in the 70's.

Next, take a look at the ingredients for the ketchup. Besides tomatoes, you will notice that two prominent chemicals are vinegar and salt. A little internet research will show you many other science experiments that use vinegar and salt for doing the same thing as the ketchup. If you want to be sure that the tomatoes are not responsible for cleaning the pennies, try using some tomato sauce that does not contain vinegar or salt.

After some experimentation, you will probably find that the vinegar and salt are the important ingredients but are they both necessary? Lets find out. Start with four small cups. Put about an inch of water in one. That will be our control. The control does not contain any of the chemicals that we are testing. If it cleans the pennies too that would tell us that the reaction happens, even without the vinegar or salt. Label this cup "Control."

In the second cup, put about an inch of vinegar. Label this one "Vinegar."

In the third cup, put about an inch of water, and then add a teaspoon of salt. Give it a quick stir to dissolve the salt. Label this one "Salt Water."

In the fourth cup, put about an inch of vinegar, and add a teaspoon of salt. Give it a quick stir to dissolve the salt. Label this cup "Vinegar and Salt."

Now, you are ready to do some testing. Lets start with the Control. Dip one of the tarnished pennies halfway into the water, and hold it there for 30 seconds. Remove it from the water, rinse it, and put it beside the Control cup.

Do the same for each of the other cups. Be sure to give each 30 seconds, and be sure to rinse the penny to remove any vinegar or salt. Place each penny beside the solution you used to test it.

Results

OK, now what did you find? If your results were like mine, you found that neither the water, the vinegar, or the salt water did much, if anything to the pennies. The mixture of salt and vinegar was very effective at removing the tarnish.

So what is happening? The tarnish on the penny is copper oxide, and a chemical reaction with the vinegar will actually dissolve it. Then why did the pure vinegar not work? With the penny and the vinegar, you get a series of chemical reactions that form a circle. One reaction removes the copper, but just as quickly, another reaction puts it back. In chemistry, this is known as an equilibrium reaction.

The trick is to add something that will interrupt that equilibrium. You want a chemical that will grab the copper before it can be put back, and the table salt does a very good job of that.

What is it about the table salt that grabs the copper? Table salt is sodium chloride. When you put it in water, it separates into sodium ions (charged atoms) and chlorine ions, but is it the sodium or the chlorine that grabs the copper. An easy way to test that is with a different kind of salt. One of the common salt substitutes is potassium chloride. You can find it beside the regular (sodium chloride) salt at the grocery. In a fifth cup, put about an inch of vinegar and stir in a teaspoon of potassium chloride. Does it work the same as the table salt? If so, then it is the chlorine that grabs the copper. If not, then it is either the sodium, or the combination of sodium and chlorine.

You can look deeper into the vinegar as well. Will it work with other acids? Try using lemon juice (citric acid and ascorbic acid) or carbonated drinks (carbonic acid). Carbonated colas also contain phosphoric acid. Again, remember safety. Look for acids from your refrigerator and spice cabinet, not from other household chemicals.

Link to Penny Chemistry, part 2

Dissect a bird to compare its skeleton with ours.

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Two weeks ago, I mentioned that I had a lot of fun experimenting with carbonated soda (and drinking it) and that I should do an experiment with chocolate. I got quite a few e-mails suggesting experiments with chocolate, but this one was the most common. It has to do with the white discoloration that you sometimes find on old chocolate. For this week's experiment, you will need:

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It is hurricane season here in Florida, but luckily this has been a very calm season so far. We still have to be sure to be prepared, just in case. I came across the idea for this experiment while reviewing some of the emergency information. Often during hurricanes, the water supply is contaminated and it is necessary to boil your water before drinking it. All of the information sheets say that this makes the water taste flat and they give several different ways to "fix" the taste. To see how boiling changes the taste, 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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This week's experiment comes from a question that was sent to me by Hashi, one of the members of the Experiment of the Week list. She noticed that smells were stronger while taking a shower and asked why. To investigate, you will need:

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For this week's experiment, we are going to investigate a very important substance which most of us take for granted. Salt. While we hardly think about it as we sprinkle it on our food, in the past, salt was a very important and valuable substance. In addition to enhancing flavor, it is a vital substance in our diet. Before refrigeration, it was a very important way of preserving food.

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I really like plums. Several days ago I picked up several from the grocery, but when I tasted one, it was hard and too sour. Like most fruit, plums are picked before they are ripe, so they will make it to the grocery without getting mashed. What I needed was a way to get the plums to ripen quickly. Luckily, with a little science, it is easy. You can try this too. You will need:

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This week's experiment should be familiar to any of you that have ever cooked pancakes. As my mother taught me, and as you will find in most cookbooks, in order to tell if the skillet is hot enough for pancakes, you dip your fingers into some water and then shake a few drops onto the skillet. If the drops just sit there or if they hit the skillet and boil, then it is not hot enough. As the temperature of the skillet increases, you reach a point where the drop of water seems to bounce and glide around the skillet. Then you know that the skillet is hot enough for pancakes. This is called the Leidenfrost Effect, and that is what we want to observe now.

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For this week's experiment, we are going to make a ball of oil. Don't worry, this is not nearly as messy as it sounds. You will need:

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This week's experiment is a fun one and a yummy one too. (I was hungry while I was choosing it.) We are going to experiment with the impact that vitamin C has on the browning of fruit.

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This experiment comes from a series of news spots that I saw regarding the spring equinox. The equinox occurs on the day when winter changes to spring and when summer changes to fall. There is a persistent story that during the equinox is the only time that you can stand an egg on its end. I did a news search and found hundreds of articles from newspapers and television with stories about this. In reality, the equinox has nothing to do with it and your chances of standing an egg on its end are the same all year round.

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