Weird Science: Rising Water - Hawaii News Now - KGMB and KHNL

Weird Science: Rising Water

HONOLULU (HawaiiNewsNow) - Dr. V joins us this morning with an experiment that involves rising water and candles...

 

Dr. V Show: Rising Water

May 4, 2010

 

Things you need:

  • Pie pan or dish
  • Candle and matches
  • Small neck jar or juice bottle
  • Food coloring
  • Water

 

The experiment

Please perform this and all experiments under the supervision and with the assistance of an adult. Secure the candle to the center of the dish. Then fill the dish will a few drops of food coloring and water, almost to the edge. Then light the candle and carefully cover the candle with your bottle. What happens to the candle? What do you see in the bottle? What happens to the water level in the bottle? Try it again. Does the same thing happen?

How does it work?

Why does the candle go out when you cover it with the bottle? What does the candle need to burn? It needs a fuel source, wax, heat, the flame, and oxygen. When you cover the candle with your bottle, you are cutting off the candle's source of oxygen. The candle uses up all the oxygen available in the bottle and then can no longer burn. Because there is no oxygen in the bottle, the other gases (nitrogen, carbon dioxide) left in the bottle exert less pressure than the atmosphere pushing down on the water outside the bottle, causing the water to rise up into the bottle. There is also another factor at work. When the candle is lit, it heats up the air in the bottle, causing it to expand. You may even see some bubbles escaping from under the bottle while the candle is lit. After the candle goes out, the air in the bottle cools off and contracts, pulling more water into the bottle as well. 

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