• Soda consists primarily of water, dissolved carbon dioxide, sweetener and flavoring.glass of soda image by Kalani from Fotolia.com
  
  Soda, with its fizzy quality and sugary good taste, makes for fun science project material. On one hand, kids can relate to it and it's generally something they enjoy. On the other hand, it provides a handy vessel to explain various phenomena in chemistry and physics.
  
  

Soda Cannon

• As you may know, if you drop Mentos candy into a two-liter plastic bottle of Diet Coke, an immediate, vigorous reaction ensues: A foam of soda shoots out of the bottle with impressive force, with the geyser sometimes gushing over 9,000 millimeters (i.e., 30 feet).
  
  The science behind this reaction is a good opportunity to teach children about chemical polarity. What causes the reaction is that the candy has a very rough surface at the molecular level. You can see that for yourself with the naked eye: Mentos look fairly smooth, but they're not shiny and they feel slightly abrasive. These tiny bumps on the candy's surface disrupt the polar bonds between water and carbon dioxide in soda, pulling carbon dioxide molecules away and creating extremely effective bubble formation spots. Essentially, the candy causes all the carbon dioxide in the soda to separate out from the water in only a few seconds. This leads to the violent spraying reaction.
  
  Diet Coke and Mentos are not the only compounds that will work, but this is the classic and most effective combination. Additionally, sugar-free sodas leave less mess to clean up, and are less of an attractant to pests.
  
  

Soda Balloon Pump

• The carbon dioxide dissolved in soda is unstable: If you leave the soda bottle open, the gas will slowly escape and the soda will turn flat. You can make use of this property to conduct a science demonstration illustrating what happens.
  
  To perform this demonstration, open a fresh two-liter bottle of soda and immediately secure a balloon around the top. Make sure the balloon is on very tightly; you might even use a clamp. Over the next five minutes to half hour, the balloon will slowly expand with carbon dioxide gas escaping from the soda. Eventually, either the balloon will pop under the pressure of the accumulating gas, or the gas will reach an equilibrium point, at which the compressed gas in the balloon "pushes back" against any more gas escaping from the soda.
  
  

The Burp Trap

• Kids often like experiments in which they can actively participate, and this one is very well-suited to that, as it amounts mostly to an excuse to drink soda and burp. The experiment goes like this: You drink a large amount of soda very quickly, without burping, and then you immediately lie down on your back. You can then stay there for as long as you like. What you will find is that it's very difficult to burp. Then, as soon as you sit upright, you will almost immediately be able to let out a big belch.
  
  This works because the liquid contents of your stomach are much more dense and heavy than the carbon dioxide gas, the liquids sink and the gas rises to the highest point in your stomach. When you're sitting or standing upright, the highest point is where your esophagus is, and the gas can escape out your mouth as a burp. However, when you're lying down on your back, the highest point in your stomach is toward your belly button. The gas has nowhere to go. So, for the most part, it will stay there until you sit up again.