Wednesday February 8 2012
density

Panning for Iron

Anonymous: 

Yesterday's walk on the beaches of New Zealand gave me a great experiment. I was playing with the ironsand, a very heavy, black sand made of titanomagnetite. There is a large deposit of ironsand on the beach at the farm. In trying to sort the different minerals, I was reminded of my gold panning trip to the Carolinas back when I worked at the Memphis Pink Palace Museum, in Memphis, Tennessee. To try your hand at "gold panning," you will need:

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This project has science fair potential.

Floating Bubbles

Anonymous: 

This week, we are going to produce some floating bubbles. Our bubbles will be filled with ordinary air, and will be floating on a layer of a heavier gas. To try this, you will need:

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Invisible Candle Snuffer

Anonymous: 

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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Can Water Float?

Anonymous: 

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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Half a Water Balloon

Anonymous: 

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


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The Right Answer

Anonymous: 

Sometimes the right answer is not the only answer.


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The Science of Pizza

Anonymous: 

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


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Wrong Way Balloon

Anonymous: 

Why do balloons act crazy in your car?


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Candles in a Jar

Anonymous: 

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


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Candles in a Jar, Part 2

Anonymous: 

The answer to the last video's challenge.


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Cartesian Diver

Anonymous: 

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


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Light as Air

Anonymous: 


Select the player that works best for you.

Slow Connection High Speed Flash High Speed Quicktime

When we say that something is as light as air, what does that really mean?

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Freezer Fun

Anonymous: 

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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