Warning! This experiment uses fire. Be very careful and be sure an adult is around to help.

This time we are going to explore a gas called carbon dioxide. It plays an important role in the lives of plants and animals, and it has very specific chemical properties. We can use those properties to do some surprising things.

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There are many things that will float on water: pieces of wood, wax, Styrofoam, and many other things. They float because they are less dense than the water. Now for the question. Can water float on water? Is there a way to make water less dense?

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Why is half a water balloon different from a full one?

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Sometimes the right answer is not the only answer.

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Is the cheese on a pizza really hotter than the crust?

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Why do balloons act crazy in your car?

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Which will go out first, the tall candle or the short one?

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The answer to the last video's challenge.

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Make a diver that will rise and fall at your command, if you know the science.

This week's experiment is a simple one. It is one of those things that you have experienced over and over, but might not have thought much about. To try it, you will need:

- a freezer
- some ice cream (Optional for some people. Required for me.)

First, open the freezer, remove the ice cream, and close the door. Now for the difficult part. Immediately, open the door and put the ice cream back.

You will probably notice that it is much harder to open the freezer door the second time. Why? It is not just because you want to keep the ice cream. It is definitely more difficult to pull the door open.

The air inside the freezer is cold, which makes it more dense than room temperature air. When you open the freezer that cold, dense air flows out, and is replaced by lighter, warmer air. When you close the freezer door, the air inside gets colder. As its temperature falls, it contracts, which creates a lower air pressure inside the freezer. When you try to open the door the second time, the higher air pressure outside is not balanced by the pressure inside. Since there is more pressure pushing in, if it much harder to open the door.

If the experiment does not work well for you, try removing some of the frozen foods from your freezer. The more air space that you have, the better the experiment will work. If it still does not work well, examine the seal on the freezer door. If the seal is broken or damaged, it would let air in to equalize the pressure. That also means that it is letting the cold air flow out of your freezer, which is not good.

Now, the second time that you open the freezer door, it is not really necessary to put the ice cream back. It is perfectly OK to keep it out long enough to scoop some into a bowl. That will let you test to see whether the pressure has equalized by the time you finish eating, and go back for seconds.

Have a wonder-filled week.

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Floating M's

Science. Chocolate. What more do you need in an experiment?

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Hot and Cold Water

Why would an ice cube cause the water in a glass to mix faster?

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One Glass Musical

Making music with a glass of water.

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Rolling Bottles

Experiment with force, and motion, and solids, and liquids.

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Soil Types

Exploring the science of dirt.