Sunday, January 17, 2010

Tip of the Iceberg - Experiment #326

"If all the icebergs in the seas were to melt, would the sea level rise? This very simple experiment will give us the answer, and it's based on a very important compound chemists study - water!

You will need:
glass
warm water
6-8 ice cubes

What to do: Place as many ice cubes as you can into a glass; then fill the glass to the brim with warm water. Wait.


What happens: When the ice cubes melt, the water does not overflow.


Why: The ice cubes simply displace the water in the glass, or the amount of ice that melted was exactly equal to the mass of the ice cubes below the water. Like the ice cubes in the glass, the main part of an iceberg is under water. If all the icebergs were to melt, as did the ice cubes in our experiment, the sea level would remain the same. (It's a different story if ice stored on land [like glaciers] were to melt).

What happened when CKS tried it?: It took almost 3 hours for the ice cubes to melt. There is about half a dollar-size puddle of water in the plate under the glass. The glass is so cold that it's misting up and gets foggy and water starts to form. CMS calls it 'condensation' on the outside of the glass. The water in the plate is coming from the air! Water is condensing from the air and forms drops on the glass. No water spilled over the top of the glass so icebergs melting in the sea would not raise sea level!

CKS rating: 2 stars - I'd rather eat my broccoli.

2 comments:

  1. Only two stars? what you need is a Mad Dad Scientist to ratchet up the excitement!

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  2. To improve this experiment, students could compare with a second glass of water containing a large rock, with a large ice cube on top of the rock. Wait for the ice in both glasses to melt, and compare the results. Which one overflowed?

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