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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For this week's experiment, we will examine something that has caused problems for Moms throughout the ages. While washing up, someone leaves a towel hanging over the side of a sink full of water and mysteriously, the water all winds up on the floor.

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This week's experiment came to me from my good friend Bob Cox. He told me about the trick and wanted to know why it worked. It took some thought and testing to come up with a theory of what is happening and then several e-mails to experts to confirm that I was on the right track. For this week's experiment, you will need:

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Can you lift an ice cube out of a glass of water with a string? Try it and see.

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Science can be as simple as blowing bubbles in your milk.

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Make a tasty snack while learning about the science of butter.

This week's experiment is simple, and delightful. We will grow some beautiful crystals. Often, growing crystals can be a fairly long, involved process, but this method is incredibly easy. To try this, you will need:

- a disposable plastic or paper cup
- epsom salts
- water
- a refrigerator
- paper towels

Place 1/2 cup of epsom salts into the cup. Then add 1/2 cup of HOT water. You don't want the water to be boiling, but you want it to be hot enough that it is uncomfortable to put your finger in. Our hot water heater is set pretty high, and that worked well, straight from the faucet. If your hot water is set lower, heat it in the microwave for about 30 seconds or so. Don't heat the water in the plastic cup, as the cup will melt and make a mess. (That is the voice of experience talking!)

Stir the hot water and epsom salts well, to allow most of the salt to dissolve. It should not all dissolve. If it does, add a little more. When it is well stirred, place it in the refrigerator, with a small sign saying "Danger! Science experiment!" or something similar, to be sure that no one drinks it.

After three or four hours, examine the cup. You should find that the bottom of the cup has a beautiful cluster of needle-shaped crystals. At that point, carefully pour the water into the sink. Then cut the side of the cup, to allow you to lift the crystals out of the cup. Place them on a couple of folded paper towels to let them dry. If they fall apart, or if you are not pleased with the result, put them into another cup of hot water, and try again. You can regrow the crystals over and over.

OK, so what is happening? Solubility (the amount of something that will dissolve) is tied to temperature. The hotter the water is; the better it is at dissolving the epsom salts. If you had a way to see the atoms along the edge of the crystals, you would notice that some of magnesium sulfate (epsom salts) was constantly leaving the crystal to dissolve in the water, while other bits of magnesium sulfate constantly leaving the water to join the crystal. If everything balances, then the crystals stay the same size.

On the other hand, if the water is hot, the extra energy lets more of the salt leave, throwing off the balance. That means that the solid epsom salts will dissolve, until it reaches a new balance. At that point, the salts stop dissolving.

When you put the cup in the refrigerator, heat energy from the cup moves to the surrounding area. With less heat energy in the water, the balance shifts again. Now you have more epsom salts joining the crystals, so the crystals grow. This will continue until things reach a new balance. At that point, the crystals stop growing.

If you want to experiment further, you can continue to play with that balance point. Once your crystals have grown, pour off the water. In another cup, mix another batch of hot water and epsom salts. This time, wait until the water cools almost to room temperature, and then carefully pour it into the cup with the crystals from your first experiment. This time, do not stir! Put it in the refrigerator.

If you get the balance right, then your original crystals will not redissolve completely. As the solution cools, more magnesium sulfate will be added to the original crystals, causing them to grow larger. You can try repeating this several times. If your balance is off, and the crystals dissolve, then just heat the water again, and start over. When you are done, you can let the crystals dry and put them on your shelf. If they get broken or dusty, just dissolve them, and grow them again.

Have a wonder-filled week.

This week's experiment idea came to me while I was waiting for our lunch. The proper drink to go with your Memphis Bar-BQ is sweet tea. Now, you may not think that is unusual, but true, Southern sweet tea is a very different drink. The difference is based in the science of chemistry. To experience this, you will need:

2 pans
water
tea bags
sugar

WARNING: For this experiment, you will have to boil water. Be sure to get permission and be safe.

Put two cups of water into each pan. Heat the water until it boils. Add a couple of tea bags to each pan. To one pan, add 2 tablespoons of sugar. After boiling for a few seconds, turn off the heat and let them cool. Once they are both cooled, add two tablespoons of sugar to the unsweetened tea. Be sure to mark the pans, so you can tell which is which. Once the sugar is dissolved, taste each one. You will find that the tea that was sweetened while it was hot is sweeter. Why?

Your first thought might be that more of the sugar dissolves in hot water than in cold. That is why we only used 2 tablespoons of sugar. We want all of it to dissolve, even in the cold tea. With the same amount of sugar in each, they should both taste the same, right? Then, why is one sweeter?

The tea that was sweetened when it was hot now has a different kind of sugar in it. Yes, there are different kinds of sugar. The sugar that we normally use is called sucrose. Sucrose is a sugar that plants make and use to store energy. When you add the sucrose to the hot tea, a process called inversion takes place. The sucrose breaks down into two other sugars, glucose and fructose. This combination, called invert sugar, is about 10% sweeter than the sucrose it was made from. This process of inversion is very useful. Bakers use invert sugar to make confections sweeter. Bees use enzymes to do the same thing when they are making honey.

Now, true Southern sweet tea is SWEET! In addition to inverting the sugar, the hot tea allows you to dissolve more sugar in the tea. This combination is one that may be too sweet if you are not used to it. If you want to try the real thing, use about a cup of sugar for a quart of tea. Chill it until it is very cold and serve it over ice. Then all you need is some Memphis bar-BQ, some cole slaw, baked beans and some banana pudding and you are all set for a feast.

This week's experiment is a favorite of mine, which won't be a surprise to anyone that has been on my experiment list for long.  To try this tasty experiment, you will need:

• 2 glasses
• carbonated soda
• ice cream

For this experiment, we will make two ice cream sodas.  Although both will contain exactly the same ingredients, they will be very different.

Start by filling one glass half-full of soda.  Then add a scoop of ice cream.  In the other glass, start by adding a scoop of ice cream, and then pour the soda into the glass.

You should notice a big difference between the two mixtures.  The glass where you added the ice cream first will have lots of thick, long lasting foam, while the glass where the ice cream was added after the soda has very little foam.  Why is there such a big difference?

There are two things that contribute to the difference in the foam.  First, the carbonated soda contains quite a bit of carbon dioxide gas dissolved in it.  It may seem strange to think of a gas dissolving in a liquid, but it is quite common.  If you watched the Watched Pot video, you may remember the bubbles of gas that appeared before the water started to boil.  Those bubbles formed from gases that were dissolved in the water.

The soda is supersaturated with carbon dioxide, which means that it contains more of the gas than would normally dissolve in it.  As long as the soda is undisturbed, the carbon dioxide escapes very slowly, but you can speed up the process by adding bubbles.  The bubbles provide more surface area for the gas to escape from.  As the gas escapes, the bubbles grow larger, providing even more surface area.  

You can see a very good example of this with an unopened bottle of soda.  If you give it a hard shake, and then open it, you are in for a mess.  Shaking the soda introduces lots of tiny bubbles into the soda, providing plenty of places for the carbon dioxide to come out of solution.  On the other hand, if you shake the soda, and then let it sit for a while before opening it, the bubbles will have time to float to the surface and pop.  In that case, when you open the soda, it stays in the bottle.

Another example of bubbles causing foam is the classic Mentos and Coke experiment.  The candy has a porous surface, which produces many tiny bubbles.  You can get similar results by dropping pieces of chalk into your soda, as it also has a very porous surface, but I don't recommend drinking the soda afterwards.

Now back to our ice cream.  Ice cream contains a LOT of bubbles.  In fact, a carton of ice cream may be as much as half air.  Those bubbles are important, as they keep the ice cream soft and smooth, instead of hard and crunchy like an ice cube.  

When you pour the soda into the glass first, microscopic bubbles from irregularities in the sides of the glass serve as a starting place for the foam.  Most of the carbon dioxide bubbles form and pop before the ice cream is added.

OK, so why is it any different when you add the ice cream first?  The ice cream has lots of tiny bubbles of air, so much more of the carbon dioxide comes out of solution.  If you taste the soda afterwards, you will find that it is quite flat, with no fizz left.  But, ice cream also contains chemical thickeners, to make it smoother and creamier.  As you pour the soda over the ice cream, some of the ice cream melts, letting the thickeners mix with the soda.  Just as they thicken the ice cream they thicken the foam, making it much firmer, and much longer lasting.  Instead of quickly popping, this time the foam stays long enough for you to enjoy eating your tasty treat.
   
So although both recipes use exactly the same ingredients, the order you add them makes a big difference, although both turn out quite tasty.  And keep in mind that an important part of science is that experiments should be repeatable, so you might want to repeat the test several times, just to be sure of your results.

Have a wonder-filled week.

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Clear Ice

What causes the cloudy look in ice cubes, and how can you get rid of it?

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Soda Water Fountain

My version of the Mentos and Coke experiment, from years before it was popular.

This week's experiment is a combination of two past experiments. We are going to combine the idea of the Dancing Raisins with the Cartesian Diver. You will need:

- a bottle of clear, carbonated soda. It needs to have a screw on cap.
- raisins

First, if the bottle of soda has a label, remove it so you can see inside. Carefully remove the cap. Drop in 5 or 6 raisins and quickly put the cap on tightly. Watch the raisins. They should sink to the bottom, with lots of tiny bubbles rising from them. After a few seconds, one or more of them will probably begin to rise. As soon as a raisin begins to rise, give the bottle a good, hard squeeze. As you do that, you should see the raisin begin to sink again. Release the pressure and the raisin begins to rise again.

Why does it do that? Lets take it one part at a time, starting with the bubbles. Where are the bubbles coming from? From the soda, right? The soda has carbon dioxide gas dissolved in it. This gas escapes, forming bubbles.

OK, so why do more bubbles form on the raisins? When you drop the raisin into the soda, its wrinkled skin traps lots of tiny air bubbles. These bubbles act as a starting point for more bubbles. As carbon dioxide gas moves from the soda to the bubbles, they get larger and larger. When they get large enough, the raisin begins to float.

Why does the raisin float? For that matter, why does anything float? If something weighs less than the same volume of water, it will float. For example, a cubic foot of Styrofoam weighs less than a cubic foot of water, so it floats. A cubic foot of steel weighs more than a cubic foot of water, so it sinks. The raisin is denser than the water, so it sinks. When the bubbles form, the combination of raisin and air weigh less than the same volume of water, so they begin to float.

OK, so far, so good. If you don't disturb things, the raisin will rise to the surface, where some of the bubbles will probably pop, letting the raisin sink again. But what happened when you squeezed the bottle? Why did the raisins sink? At first, you might think that you shook enough bubbles loose to let it sink again, but as soon as you stopped squeezing, it began to rise again.

So what would squeezing do? Squeezing the bottle makes it smaller, which means that the stuff inside has to get smaller. You can't make water smaller by squeezing it, so that means the air inside the bottle gets smaller. If you watch the top of the bottle, you can see the air space at the top getting smaller. The bubbles also get smaller. The smaller bubbles still weigh the same, since they contain the same amount of air, just squeezed into a smaller space. That makes them denser, letting the raisin sink. That is the idea behind the classic science experiment called the Cartesian Diver, which is the reason I called this experiment the Cartesian Raisins.

After a short time, you will notice that the raisins stop rising. Now what is wrong? Nothing. As the pressure builds up inside the bottle, the bubbles stop forming. All you need to do to get things going again is loosen the top. As soon as you hear the hiss of escaping air, you will see a burst of bubbles and some of the raisins will almost shoot to the surface. Tighten the cap and you will have another minute or two to play with the Cartesian Raisins.

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Lifting an Ice Cube

Lifting an ice cube out of a glass of water with a string is easy, if you know the science.

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Viscosity

A simple, scientific test to see how "thick" a liquid is.

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Is it Safe to Heat Water in a Microwave Oven?

You have probably heard about this, but is it true?