Chemistry Demonstrations and Fourth-graders: A Volatile Mixture?

Last week, I attended the regional meeting of the National Science Teachers Association held here in Minneapolis. I enjoyed seeing so many enthusiastic science teachers attending the sessions and wandering around the exhibit hall.

But when did schools start hiring such young teachers? Nearly all of them were quite a bit younger than me. And I’m not that old!   I’m only … well, let’s just say that I’m a seasoned professional.

Instead of feeling old when I left the meeting, however, I felt young and inspired. I particularly enjoyed watching some of the chemistry demonstrations that presenters were teaching to the teachers. As we participated in these hands-on activities, I could sense the energy and excitement rising in the room. It was the same feeling I get when I put on chemistry shows in my children’s classrooms.

I even started thinking back to the first chemistry show I ever witnessed, when I was a fourth-grader at Meeker Elementary School in Ames, Iowa.

Several years ago I wrote up my memories of that chemistry show, and here’s a copy of that brief essay:

The magic of chemistry first reveals itself to me in 1965, during Spring Break of my fourth-grade year, when my family goes on vacation to the big city of Chicago. The highlight of the trip is the visit to the Museum of Science and Industry. As we amble through the museum, we learn about coal mines and submarines. We see a plastic human heart pumping red and blue fluid throughout a life-size model of a human body. We find out about all kinds of machines, from levers and pulleys to the internal combustion engine. And at 2:00 pm, we gather on bleachers in an open area near the lobby to watch a demonstration of “The Wonderful World of Chemistry.”


I’m seated in the front row. Facing us, on a little stage, is a long table covered with glass bottles of various shapes, sizes, and colors. Placed at one end of the table are a banana, a wooden board, and a pink rubber ball. The ball is exactly the same kind as one I use to play “bounce and catch” at home on my front porch.


The noisy crowd of parents and children quiets down as a man in a white coat steps behind the table and faces us. A red rose is pinned to his lapel. A bright blue balloon rises above him, held in his right hand. He’s wearing glasses that have little plastic shields on the side. This man sure has my attention.


He starts the show by pouring two colorless liquids together, turning them first pink and then purple as he says some magic words. As he mixes other liquids and solids, he creates smoke and fog, makes a volcano overflow, and sets off a loud explosion.


Finally, he tells us that it’s time for the grand finale. He still hasn’t touched the banana or ball. I wonder what he’s going to do with them; maybe he’ll give them out as prizes to kids in the audience. I could always use another pink bouncy ball.


He reaches below the table and pulls out a big metal container with a lid on it. He puts on heavy white gloves and uses a long set of tongs to lift the lid off the container. Fog rises from it. Using a metal scoop shaped like the ladle my Mom uses to serve punch at Christmas time, he scoops up some liquid from the container. We can all see that it’s colorless and bubbling. Suddenly he bends over and pours it on the concrete floor right in front of the audience. I can hear it splatter on the floor. I pull back away from it, just like everyone around me. We don’t want to get splashed with this mysterious bubbling liquid. But as soon as it hits the floor, it disappears. It’s gone. None of us got wet, but I did feel a puff of cool air.


The man in the white coat tells us that this liquid is called “liquid nitrogen,” and it’s colder than the coldest Chicago winter. Grabbing the blue balloon, he holds it down on the table and pours a scoop of liquid nitrogen over it. The balloon shrivels up like a huge raisin, making a crinkly sound as it shrinks. The man lets go of it, and it just lies there. But then, right in front of our eyes, it starts to grow, take shape again, and rise into the air.


Next, the man takes the banana. Holding it with his tongs, he lowers it into the liquid nitrogen container for half a minute. When he takes it out of the liquid, he grips it in his gloved hand, and he picks up the board and a nail. Using the “Banana Hammer,” he pounds the nail right into the board. We ooh and ahh and applaud. I guess he won’t be giving out that banana as a prize.


Finally, he reaches for the bouncy ball and drops it in the liquid nitrogen container. After a minute or so, he fishes it out using the metal scooper. Picking it up, he turns around and throws it at the concrete wall behind him. I get ready to grab it when it bounces back toward the audience. But it doesn’t bounce. It shatters into many small pieces. I wonder if he’ll put the ball back together as the grand finale, but it doesn’t work that way, I soon find out.


Before he leaves, however, he has one final demonstration for us. He unpins the red rose from his lab coat lapel, dips it in the liquid nitrogen, and then bangs it on the table. Tiny red pieces of frozen rose petals fly across the table. I’m not sure if I’m supposed to clap or cry. As everyone around me begins to applaud, I hesitantly join in. Even if the rose incident doesn’t sit quite right with me, I decide that chemistry is indeed wonderful, and I’m going to learn more about it when I grow up.

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Published in: on November 9, 2009 at 1:10 pm  Comments (3)  
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Just Chill, Dad

How cold has it been this winter? It’s been so cold that my teenager wore a hat to school.

Here in Minnesota, in the suburbs of the Twin Cities, high school students choose their daily outfits very carefully. Many different factors can go into the decision-making process, but weather-appropriateness is not one of them.

For some reason, at my son’s high school, more than 90% of the students refuse to use their lockers. They insist on carrying all their books, supplies, and outerwear around with them from class to class. Parkas, boots, mittens, and snow pants just don’t figure into the fashion equation. (Maybe we should install space heaters in their backpacks and shoulder bags.)

Our educational system here in Minnesota (just like everywhere else) is becoming more and more cluttered with standards and assessments—for math, science, writing, and reading. I’m tempted to start a citizens’ revolt to also demand sartorial standards. (“The student will learn to observe the weather conditions, using electronic information or actual physical observations. The student will learn the properties of rain gear and cold weather gear. The student will choose the appropriate outerwear at least 70% of the time.”)

I guess I shouldn’t wait until the educational system does my parenting job for me. As a parent, I have to draw the line somewhere, even with teenagers. It’s my moral, legal, and paternal obligation.

So here are my tough rules:
• For cool weather, my son can’t wear shorts when it’s below freezing (that’s 32 degrees Fahrenheit). Sometime in late fall, he has to switch to long pants or jeans.
• For really cold weather, I insist on a hat when the wind-chill temperature drops into the frostbite zone—at -20 degrees or lower. At these temperatures, my childhood memories take over, and I can still hear my fifth-grade teacher, Mrs. Mathre, saying, “Wear your hat at recess. You lose 2/3 of your body heat through your head.”
• My rule for wet weather? Well, I gave up on that one. If they want to get soaked, suffer wet hair, and wear soggy clothes all day, then go right ahead.

According to the National Weather Service website, last week’s coldest reading was an air temperature is -27 degrees Fahrenheit, and the wind chill temperature was -41 degrees. Scientific studies have shown that, in these conditions, exposed skin will begin to suffer frostbite in ten minutes. Just to put that amount of time in proper perspective—that’s about the time required to read seven status updates on Facebook, write four text messages, or listen to three songs on an mp3 player.

I would hope that frozen skin might be a disincentive for teenagers. More importantly, however, those bitterly cold temperatures aren’t too good for cell phones, iPods, and body piercings either.

Maybe if I make a YouTube video about frostbite, set it to some hip-hop music, and release it to the Internet, my teenager will finally get the message.

Published in: on January 24, 2009 at 10:18 am  Comments (1)  
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Brrrrrrr…..

Brrr… It’s verrry cold in Minnesota. This morning, the air temperature in the neighboring suburb of Eden Prairie is -21 degrees Fahrenheit. On the metric temperature scale used by all scientists and by the general public in nearly every country in the world, the temperature is -29 degrees Celsius. [Only the United States, Liberia, and Burma (Myanmar) haven’t yet switched to the metric scale for measurement.]

When the temperature gets this low, I start surfing the web pages of the National Weather Service so I can find the lowest official temperature that I can honestly claim to others. For example, this morning’s low temperature in the Twin Cities metropolitan area ranged from -21 (Eden Prairie, Flying Cloud Airport) to – 18 (Bloomington, Minneapolis/St. Paul International Airport) to -24 (Lakeville, Airlake Airport).

My 17-year-old son must have inherited the same cold-seeking gene.  He told me yesterday that he had been roaming the internet to look at temperatures; he reported that our temperatures in Minnesota were the same as those at the South Pole (where it is currently summer).

The same sort of cold competition can be found in northern Minnesota, where three different towns (International Falls, Tower, and Embarrass) all claim to be the coldest place in the “lower 48.” This morning, the temperature in International Falls was -40. The lowest recorded temperature in Minnesota was -60 (Tower, MN, February 2, 1996).

During that extremely cold winter of 1996, the temperature here in Minneapolis dipped to -32 degrees Fahrenheit. I was thrilled. I bought several thermometers to keep outside on the deck, so I could monitor the cold. As long as it was going to be that frigid, I really wanted the temperature to plunge to -40 degrees. For me, that’s a magical temperature, for several reasons.

First, it’s the one temperature at which the Fahrenheit and Celsius scales coincide. -40 degrees Fahrenheit is also -40 degrees Celsius. At that particular temperature, the residents of the United States are international citizens in the world of measurement. Like the early Christians on Pentecost, we can understand each others’ languages.

And there’s a second reason I’m a big fan of -40 degrees. At just about this temperature, mercury will freeze solid. The freezing point of mercury, at standard atmospheric pressure, is -38.83 °C or -37.89 °F. If you’re using a mercury thermometer (not as common today as they used to be), it stops working at this temperature.  You can’t ever reach -40 on a mercury thermometer.

Just about a year ago, I was thinking about even colder temperatures, while working on a project for public television. My assignment was to prepare a timeline that showed the progress of low-temperature science, a timeline that would accompany the “NOVA” television program, “Absolute Zero. Here’s the hyperlink for my timeline contribution to the project, Milestones in Cold Research.

Here are several fun temperature facts I learned while working on that timeline project:

• The thermoscope (a predecessor to today’s thermometers) was invented by Galileo Galilei in the 1590s. The first modern-style, sealed-glass thermometer was invented in 1654.

• The world’s first home air conditioner was installed in Minneapolis, Minnesota—in 1914 by a man named Charles Gates. The machine, built by Willis Carrier, was almost 7 feet high, 6 feet wide, and 20 feet long. (Of all places to install the first home air conditioner, why in Minnesota?)

• At extremely low temperatures (20 nanokelvin or 0.00000002 degrees above absolute zero), a new form of matter can be observed. Called the Bose-Einstein condensate, it was the subject of the Nobel Prize in Physics in 2001.

Now that I’ve spent so much time thinking and writing about cold, I think I’ll stay inside and read a good book in front of my fire.   I’ll probably choose a book about the cold–perhaps the famous short story by Jack London, “To Build a Fire,” about a man and his dog trying to survive in the Yukon in temperatures of 75 degrees below zero.

Published in: on January 13, 2009 at 8:31 am  Comments (3)  
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