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I was twelve years old, Mrs. Engels lived next door. She was an engineer
in the Oak Ridge Nuclear Energy Laboratory on the other side of town.
On weekends, in spring and summer, she would work in her garden or
lie and read thick books in a hammock that swung between two small
maple trees in her backyard. I loved to visit and watch the vegetables
sprout and grow, flower, and die in Mrs. Engels’ garden. I loved
her bug and fertilizer stories. One day she asked me to run home, find, and bring back a metric ruler. It had to be metric! I ran, I found, and I did. Mrs. Engels closed her book, sat up in her hammock, and placed the ruler on the book. Carefully she put her thumb down on the metric ruler and put her first finger exactly one centimeter away. (I knew it was one centimeter. Mrs. Engels always talks out loud about what she’s doing. At least when I’m around.) Then, she held up her hand, her fingers apart just so, and asked me, “What do you see between these fingers, Jenny?” “Nothing,” I said, squinching my nose and peering closely. “Try harder,” said Mrs. Engels. “Still nothing. Your garden?” “Good. Now imagine a small cube between my fingers, exactly one centimeter on each side, with invisible wires as edges keeping it perfectly square. See it?” “Yes, I guess.” and I’m sure my nose was really squinched-up because it still always get that way when I look at something very hard. “Good,” she said. And carefully she placed the cube on her book, pulled the pencil out from behind her ear, and as she wrote on a piece of paper, she said, “In that cube there are 26,880,000,000,000,000,000 (she talked each zero out loud) molecules of gas all bumping into each other, pushing against the side of our invisible cube.” She picked up the cube and asked, again, “Can you see them?” I had to be squinching hard now, but I still couldn’t see anything but her garden. “Nope.” “Well, they’re there. And every time we breathe, we breathe in a couple thousand of those cubes of gas. Do you know how what molecules are?” “Yes,” I said. Having heard about molecules but never having seen one. “Can you guess how many different types of gas molecules there are in our cube? I was at a total loss now, and admitted it. She never seemed to mind my not knowing something. She never made me feel stupid. She’d just smile, nod and continue, “Ten different types of molecules, maybe more. It’s hard to tell. But it’s a clear day, so I’d guess ten. Do you know which three types are the most important?” I took a stab at that one, “Oxygen?” “Good,” she said, “and?” Again, I didn’t know. “Okay. Nitrogen and Carbon Dioxide. The plants need carbon dioxide to make more oxygen. By why nitrogen, do you think?” “I don’t know. I don’t remember talking about nitrogen in health,” I said. “Exactly,” she said, “we don’t need nitrogen, but without it, if someone lit a match, air made of pure oxygen would explode and burn the Earth and everything on it to a cinder. Now, if I give you this cube, will you do me a favor?” “Okay,” I said, not knowing what was coming next, but trusting her just the same. “Take care of the gas in that cube as long as you can. Try to keep it clean! Even though there are more molecules in your cube of air than astronomers believe there are stars in the universe, there’s a lot less cubes in the air than you might think. If you don’t watch out the natural gas molecules can get squeezed out by all kinds of dirt particles and poisonous gas molecules.” With that she carefully picked up the cube, reached out, and placed it in my turned-up my hand. I couldn’t see it, nor feel it, but there was something about Mrs.Engels that made you believe in what she said. That’s how I learned about air. How about you? Facts I Learned Later About Air and Other Cool Things. 1 m3= 1,000,000 cm3 1 m3= 2.688 X 1025 air molecules 26,880,000,000,000,000,000,000,000 1 cm3 = 2.688 X 1019 air molecules 26,880,000,000,000,000,000 1 mm3 = 2.688X 1013 air molecules 26,880,000,000,000 [Compare to the estimated number of stars in the universe 10 X 1022 100,000,000,000,000,000,000,000] The air we breathe is a big mix of gases that float around us in the form of trillions and trillions of molecules. The main ten atmospheric gases are nitrogen (N2), oxygen (O2), carbon dioxide (CO2), Argon (Ar), Neon (Ne), Helium (He), Methane (CH4), Krypton (Kr), Nitrogen oxide (N2O), Hydrogen (H2), and two “intruders,” dust, and water vapor (H20). All the molecules are moving around and bouncing off of each other. Heat gets them moving faster and faster. Cool slows them down. Wind begins with changes in temperature. |
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