By: Clare Eidson and Johnie Manuszak
Rise water Rise
It's a very popular experiment, put a burning candle on a dish filled with water, cover the candle with an inverted glass: after a little while, the candle flame goes out and the water level inside the glass rises.
About
The Process
The candle flame heats the air in the vase or glass, and this hot air expands. Some of the expanding air escapes out from under the vase, you might see some bubbles. When the flame goes out, the air in the vase cools down and the cooler air contracts. The cooling air inside of the vase creates a vacuum. This imperfect vacuum is created due to the low pressure inside the vase and the high pressure outside of the vase. We know what you're thinking, the vacuum is sucking the water into the vase right? You have the right idea, but scientists try to avoid using the term "suck" when describing a vacuum. Instead, they explain it as gases exerting pressure from an area of high pressure to an area of low pressure.
Steps
Fill a plastic cup up with water. About 9 oz. should do the trick.
Add 2 or 3 drops of food coloring to the water. This will make the movement of the water easier to see later on in the experiment.
Pour the water into the plate or pan and place the candle in the middle of the water.
Light the candle.
Cover the candle with the vase and think about what is taking place both inside and outside of the vase. What invisible thing is inside the vase? Carefully observe what happens to the water around the vase. It's bubbling! What happens to the candle flame?
Repeat the experiment several times until you can write down or draw a picture that explains why the water level rises.
Variables
Independent Variable:
The amount of matches used to make the water level rise.
Dependent Variable:
The level of the water when it rises.
