-the "Julia Child" of kids' hands-on science
- If you have an open bag of potato chips lying around, you can use that. Otherwise open a new bag.
- Put a few fresh potato chips in a glass bowl in the sunlight and wait a day or two.
- Taste one of these exposed potato chips.
- Compare it to the taste of a chip from a brand new bag.
Big difference, no? It’s enough to worry a potato chip manufacturer. There are two things that make a potato chip stale. Can you guess what they are? Okay, I’ll tell you: Air (specifically oxygen in the air) and light. So potato chip manufacturers know that if they want to keep their chips fresh, they have to remove oxygen and light. How do they do that?
Take a close look at an opened bag of potato chips. It is foil-lined to make it light proof. An unopened bag is very puffy because it is filled with a gas. This puffiness protects the chips from breaking. But the gas in the bag is not air, which is a mixture of about 20% oxygen and 79% nitrogen. It is air without the oxygen, so it’s mostly nitrogen.
You can prove this. Oxygen is needed for fire to burn. If the air around a flame is flooded with nitrogen, the flame goes out. So you can use the gas in a bag of potato chips to put out a candle. Here’s how:
- Light a candle. (Make sure you have an adult help you since this trick involves fire.)
- Cut off the corner of a new bag of potato chips.
- Gently squeeze some of the gas from the potato chip bag near the candle flame. If you squeeze too hard, it’s like blowing the flame out. You want it to go out because the nitrogen in the potato chip bag is quietly flowing into the space around the flame.
Now you know how to extinguish a flame with a bag of potato chips. You have also proved that there is no oxygen in a potato chip bag! And you know why!
Now go educate some grown-up.
Vicki Cobb’s best known book is Science Experiments You Can Eat.
The new, next revision will be out in the summer of 2016.
Vicki is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.