Science in a Bag of Potato Chips

Starring

You and Your Students!

Script By

Vicki Cobb, Education World Science Editor

Synopsis

Discover how packaging keeps potato chips fresh.

Genre

• Chemistry
• Nutrition

Required Props

• a candle
• scissors
• an unopened bag of potato chips
• matches
• a bowl
• a bag clip, rubber band, or twist tie

Show-Biz Science is scripted by popular children's book writer Vicki Cobb. Click to learn more about Vicki or to read a brief synopsis of her philosophy of teaching science. Visit our archive of archive of Show-Biz Science Activities. Watch for a new activity each week. Then chat with Vicki -- share your feedback and ask your questions about teaching science -- on our special Showbiz-Science message board. Be sure to visit Vicki's Kids' Science Page for more great science fun, a complete list of her books, and information about how you can invite Vicki to come to your school. And don't miss her library of science videos too. Or visit Vicki and other great authors of nonfiction for children at the INK Think Tank.

Setting the Scene (Background)

If a person slices potatoes very thin and fries them in hot oil, they end up with potato chips. The hot oil replaces up to 80 percent of the water in the potatoes, the slice is twice as thin as it started, and the result is crisp and crunchy, not soggy. To keep potato chips fresh, commercial manufacturers had to solve two problems:

• The chips had to be kept in the dark.
• The chips had to be kept away from oxygen in the air.

To solve those problems, potato chip manufacturers developed a bag that is 1) lined with foil to keep out light and 2) packed in nitrogen -- an inert gas that makes up almost 80 percent of air. Unlike oxygen, which is required for a flame to burn, nitrogen doesn't support combustion. So the gas in a bag of potato chips should extinguish a flame -- fun!

Stage Direction

Do the first part of this activity as a demonstration. But then you can let the kids set up their own stale potato chip experiments. You might also use this activity as an introduction to the nutritional value of potato chip -- which taste great because they are high in salt and fat.

Plot

Act I
Light a candle. Blow gently on the flame. Point out to students that your breath contains oxygen, and that your gentle blowing fans the flame; it does not extinguish it. (If you blow hard, the force of the air's motion keeps the flame from getting oxygen, and it will go out.) Use scissors to cut off the corner of a bag of potato chips to make a small hole. Aim the hole at a flame and squeeze the bag gently so you flood the flame with nitrogen. (You don't want to squeeze so hard that the force blows out the flame.) The nitrogen deprives the flame of oxygen from the air, and the flame will go out. The nitrogen also puffs up the bag to keep breakage to a minimum.

Act II
Put some of the chips from the freshly opened bag in a glass bowl in the sunlight. Leave the rest of the chips in the bag and close tightly with a bag clip, twist tie, or rubber band. Taste a chip from each group every day for a week. How do the flavors compare? Rancid potato chips won't harm you, but you'll get insight into the problem facing potato chip manufacturers -- keeping their products as fresh as long as possible.

Behind the Scenes

Potato chips are America's number one snack food. They also add to the nation's obesity problem! You might share with students the nutritional information on the bag. Pay attention to portion size -- twenty chips! One portion, or 20 chips, is 150 calories and provides 15% of your daily requirement for fat.

The End

For more fun experiments with food, check out Where's the Science Here? Junk Food by Vicki Cobb (Millbrook Press, 2006).

Article By Vicki Cobb
Education World®
Copyright © 2006 Education World

02/16/2006