# Why Does the Water Rise?

## You’ll have to watch closely...

You’ll have to watch closely and use everything that you know about air in order to explain the mystery of the rising water. You heard right! Air is the key to why the water rises in this experiment... but you'll have to do the experiment yourself to find out just how air affects the water.

### Materials

• Candle and matches
• Pie pan or dish
• Juice bottle, jar, or clear vase
• Water
• Food coloring
• Matches

This experiment requires the use of matches... and that means adult supervision.

1. Fill a plastic cup up with water.  About 9 oz. should do the trick.
2. 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.
3. Pour the water into the plate or pan and place the candle in the middle of the water.
4. Light the candle.
5. 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?
6. Repeat the experiment several times until you can write down or draw a picture that explains why the water level rises.

### How does it work?

The candle flame heats the air in the vase, 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.

A common misconception regarding this experiment is that the consumption of the oxygen inside of the bottle is also a factor in the water rising.  Truth is, there is a possibility that there would be a small rise in the water from the flame burning up oxygen, but it is extremely minor compared to the expansion and contraction of the gases within the bottle.  Simply put, the water would rise at a steady rate if the oxygen being consumed were the main contributing factor (rather than experiencing the rapid rise when the flame is extinguished).