We’re going to do an experiment where it will look like we can boil soda on command… but the truth is, it’s not really boiling in the first place! If you drink soda, save one for doing this experiment. Otherwise, get one that’s “diet” (without the sugar, it’s a lot easier to clean up).
[am4show have=’p9;p52;p91;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials:
- two beakers or two saucepans
- test tube
- test tube clamp
- stove or alcohol burner with stand
- ice
- soda (cold!)
- gloves
- goggles
Advanced Students: Download your Worksheet Lab here!
Experiment:
- Use the saucepan to heat a jar full of water until boiling (be sure to put an inch of water in the pan also or you’ll crack the jar).
- Fill one of the beakers with mostly ice and a little water. This is your ice bath.
- Fill your test tube half full with soda, and set it in the beaker with the hot water. What happens?
- Use the test tube clamp to remove the test tube from the hot water and place it in the ice bath. What happens now after you wait a few minutes?
- After a bit, place the test tube back into the hot water. What happens after a few minutes?
- Repeat this process and notice how and when the soda bubbles, and when it doesn’t. What do you think is happening?
What’s going on? The boiling point of the soda is much higher than the boiling point of water (due to the sugar added to the solution), however it sure looks like it is boiling, doesn’t it? Soda (a liquid solvent) has carbon dioxide gas (a gaseous solute) dissolved in it. When you heat it up, the increase in temperature makes the carbon dioxide comes out of the solution. Lowering the temperature makes the gas dissolve into the liquid, because the solubility of the soda is increased (how much gas you can dissolve into the solution). Gases are less soluble in hot solvents than cold, which is the opposite for solid solutes. Said another way, you can dissolve more salt in hot water than cold, and dissolve more gas bubbles in cold water than hot.
[/am4show]