This simple at home science experiment for kids will fascinate and intrigue your children as they watch water seemingly defy gravity.  The question you’ll have for them will be, “How is the water rising?”

What you’ll need:

• A pie plate
• A match
• A candle
• A lump of clay or chewing gum to hold the candle in place
• Water
• A glass (don’t use plastic)

Let’s get started!

Step 1.  Add about one inch of water to your pie plate.

Step 2.  Place a short candle in the middle of the tray.  If it doesn’t stand up by itself, use the clay or chewing gum to secure it to the bottom.

Step 3.  Light the candle.

Step 4.  Carefully place the inverted glass over the candle, setting the rim into the water.

Step 5.  Watch as the water rises and the candle goes out.  How did this happen?  Ask your children to give you their ideas and theories.   Reveal the real reason below and repeat the experiment a second time so that they can follow along.

What happened?

Notice carefully as the water rises in the glass.  While the candle goes out because it consumes oxygen, that’s not why the water rises. The water rises after the candle goes out.

• As you lower the glass over the candle, the flame heats the air inside the glass.
• The glass contacts the surface of the water, trapping a volume of warm air.
• The candle goes out and this warm air cools rapidly.
• Air that cools rapidly under a constant pressure does so according to Charles’s law, a specific version of the ideal gas law that holds the quantity of gas and the pressure constant. Charles’s law holds that the ratio of Volume to Temperature is constant.
• Since the temperature decreases, the volume must also decrease.
• Additionally, some water vapor may condense on the sides of the glass and back into the liquid water. This also reduces the total volume of gas inside the glass.

The simple answer is that fire heats the air in the glass, so the air volume increases causing positive pressure inside. As fire goes out, and the air cools inside the glass, the volume decreases lowering the pressure (forming a vacuum). Then the outside air pressure the with pushes the water into the glass until the pressure inside and outside the glass are equal.

Did you enjoy this fun science experiment for kids?  If so, check out some of the great science kits and other at home science experiments at jmcremps.com.

The instructional portion of this article was provided by wikiHow, a wiki building the world’s largest, highest quality how-to manual. Please edit this article and find author credits at the original wikiHow article on How to Make Water Rise. Content on wikiHow can be shared under a Creative Commons License.