Thursday, January 15, 2004

What Makes Soda Pop?

Pop, soda or soda-pop bubbles and fizzes because of the gas called carbon dioxide (di-ox-ide). Carbon dioxide is same gas that we breathe out (We breathe oxygen in). When soda-pop is made a whole lot of carbon dioxide is pushed into a pop can. The can is then sealed and pressure inside the can is created. The pressure inside the can is higher than the pressure outside the can. This is why the can will "pop" when you open it. The amount of carbon dioxide that the liquid soda-pop can hold depends on the temperature and pressure of the liquid. The amount of a gas that a liquid can hold is called the solubility (sol-u-bil-ity) of the gas. The "pop" at the opening is caused by carbon dioxide being released from the liquid soda-pop since the amount of gas the liquid soda-pop can hold is changed when the pressure is changed.

If you take a soda-pop right out of the refrigerator and open it up, less carbon dioxide will be given off than if you opened it after it was sitting in the sun for hours. If you lower the temperature of the soda-pop the solubility of the carbon dioxide is increased, so more gas will stay in the liquid soda-pop.

Little Lions Experiment:

  1. See if the laws of solubility hold true. Take a can of soda-pop that has been in the freezer for an hour or two, until it is cold, but not frozen. Wash out a styrofoam cup and lid from a gas-station or a fast food place, take a straw and put it in the cup. Tape around the opening in the lid where the straw goes. Take a second straw and insert in the straw from the cup and tape any joints between the straws. Insert the far end of the straw in a clear glass with water in it. You want to try to prevent any gas from leaving the cup, other than what goes through the straw to the water. Take the styrofam cup and fill it with your soda-pop. Close the lid quickly to prevent any escaping of gas. Place the cup in warm to hot water. Do not boil water with the cup in the pan or the cup will melt. Notice the carbon dioxide bubbling in the water. Does the amount of carbon dioxide given off change when you put the cup in the warm water?
  2. Find hidden gases! Look around the house for other gas hiding in liquids. Some of these imposters are hydrogen peroxide, bleach, ammonia, perfume, and cologne. Notice how some of these hidden gases smell, and some smell bad! This is because gas molecules move around a whole lot more then liquid molecules, so our nose picks them up better.