Science Projects on Which Sodas Have More Fizz

Sodas are a near ubiquitous soft drink, found in virtually every grocery store, gas station and vending machine in the U.S. Sodas come in a variety of flavors and colors, and generally vary in the level of carbonation. As such, measuring the carbonation of sodas is a popular science project that can be impressive and educational if done correctly.

Understanding Carbonation

Carbonated water consists of water and dissolved carbon dioxide, and carbon dioxide is not very soluble in water. To carbonate water, pressure must be added so the carbon dioxide dissolves into the water. When a bottle of soda is opened, the pressure inside is released and the carbon dioxide escapes. When an investigator measures the fizz in soda, he is actually measuring the amount of carbon dioxide escaping from the soda.

Visualizing Fizz

One way to determine the fizziest soda is to drop several pieces of Mentos mint-flavored candy into newly opened 2-liter bottles of soda and then compare how high the soda shoots upward out of the bottle. The surface of the candy is covered in microscopic holes; carbon dioxide bubbles collect around the holes and then quickly rise to the surface, creating a geyser of soda. This method doesn't allow for the collection of a lot of scientific data, but it does make an excellent starting point for discussing the science behind soda fizz.

Balloon Measurement

Place an empty balloon over a few different types of soda in 2-liter bottles; secure the balloon around the mouths of each bottle using a rubber band. As carbon dioxide escapes from the bottles the balloons will begin to fill up. Wait for a day and then have the students measure the balloons with a tape measure to see which balloon is larger. The soda that produces the larger balloon will generate the most fizz.

Water Displacement

Gather a graduated cylinder, a plastic tub, water, and some plastic tubing. Drill a hole in a spare plastic soda bottle cap. The hole should be slightly smaller than the plastic tubing so that when you force the tubing in the hole it seals tightly. Force the tube 1 inch into the hole. Fill the graduated cylinder with water and then fill the plastic tub halfway full of water. Place your hand over the top of the graduated cylinder, flip it over and then quickly place it upside down in the tub of water. Place the end of the tube not connected to the bottle cap inside the water filled cylinder. Unscrew the cap on a new bottle of soda and replace it with the cap with the tube in it. Shake the bottle. Carbon dioxide bubbles will rise to the top and escape through the plastic tubing into the graduated cylinder. This will displace the water inside the cylinder, allowing you to measure the amount of carbon dioxide in each soda.