# Fifth Period

## First Time Here?

Go to the first strip and
see how it all started!

Join students Sophie, Tomás, Emma, and Marcus during Fifth Period! This STEM comic strip chronicles the exciting and often hilarious adventures of a close-knit group of four friends as they learn about science, technology, engineering, and math from their kooky, inspiring, off-the-wall science teacher, Mr. Kepler. When they're not in class, these kids love to explore the vast world of STEM on their own, launching weather balloons, programming computer games, and cataloging insects, sometimes with unpredictable and highly entertaining results!

Check back on the first and third Friday of every month for a new Fifth Period strip!

October 18, 2013

### Hot Air Halloween

What the heck is going on here?! What is Emma doing outside with a hair dryer? It looks like she’s steamed up a simple plot to give Marcus a cheap scare, and all it took was a little thermodynamics! Emma knows that the hot air from the hair dryer is less dense than the cold October air. That’s because the molecules in hot air are moving around faster and more erratically than air at a lower temperature, meaning the molecules are farther apart and thus less dense. Fluids of a lower density will always rise above higher-density fluids. (Fun tip: have you ever tried to mix vegetable oil and water? See which fluid is less dense.) All Emma had to do then was find something to trap the hot air. Lucky for her, she had a ghostly looking trash bag to spare. After blowing hot air into it, she simply let it float up to Marcus’s window and—bingo—Trickery Accomplished!

Try it yourself!

You can make your own hot air spook for Halloween. All you need is a very thin plastic bag, a hair dryer, and perhaps markers or construction paper to put a scary face on the bag. After drawing or pasting some eyes and a mouth on the bag, check to make sure there are no holes. Tie the edges of the bag’s open end into knots to make the opening smaller (so the air stays trapped). Then grab a hair dryer, fill the bag with air (taking care not to touch the plastic bag to the heating element in the dryer), and watch your ghostly creation float into the night.