Collecting diet coke mentos gas:
Many of you must have done or seen the diet coke and mentos experiment, where you can get a fountain of soda streaming through the air. You probably also know that the fountain is the release of gas trapped inside the drink. But did you know that the gas is different from the air we breath? What kind of gas is it? Let’s find out!
Get your materials together
All you need are two balloons, a 1 liter bottle of diet coke, and some mentos. This should only cost a few dollars and you can buy everything at a grocery or convenience store.
Capture the gas
Now onto the fun part! Find an area outside or in a bathtub to do this. First, remove 1 mentos and push it into the balloon. Make sure you get it past the neck. Next, remove the cap of the diet coke and stretch the neck of the balloon around the opening. Once the balloon is secure, push the mentos through the balloon into the liquid diet coke. Your balloon will begin to quickly fill!
Be sure to hold the balloon over the soda nozzle. Once the reaction has slowed down (your balloon stops filling), allow the soda to return back into the diet coke bottle so you only have gas in the balloon. Then, carefully twist the balloon and detach the rubber from the nozzle. Tie off the balloon.
Test #1: Drop Test
One thing scientists use to tell gases apart is their density. Density is used to measure the amount of matter (stuff) in a given area. You probably have noticed that party balloons float in the air. That’s because they’re filled with helium, which is less dense than air, making the balloon to float. But what about your soda gas?
To compare, get your other balloon and fill it with air (just blow it up to the same size as your soda balloon). Tie it off, and drop both balloons from the same height. Which one falls first?
Test #2: Combustion
Another experiment to try is to see how it affects a candle that is burning. Have an adult help you light a candle. Take your balloon and puncture a very small hole near the rubber opening that you tied off. Get a jar about the size of the volume of your balloon, and carefully fill the soda gas into the jar.
Once the balloon is empty, carefully “pour” your soda gas onto the candle. What happens??
So what gas is in our soda?
If you guessed Carbon Dioxide, you’re right! Carbon Dioxide is put into soda to give it a certain taste and “fizziness”. You may be wondering why it put out the candle flame and sank faster than air.
Flames are the result of a chemical reaction called combustion. Oxygen reacts with the wax in the candle to produce carbon dioxide and water vapor. When we poured the carbon dioxide from the balloon onto the candle, it starved the candle from any oxygen and stopped the reaction.
The sinking of the balloon can be explained with chemistry. Carbon dioxide is made of one carbon atom and two oxygen atoms. If you look at the periodic table, you can see that the molecular weight is (12+16+16) 44. Air (in the other balloon) is about 80% nitrogen and 20% oxygen. We can see that the molecular weight of nitrogen is (14+14)=28 and oxygen is (16+16)=32. Both are less than 44, so the carbon dioxide balloon is heavier!
Chemistry can explain and predict some pretty cool things!