Thermodynamics for Preschoolers
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Once upon a time there really was a professor of physics who felt that natural laws were so self-evident that even children could understand them - even if the vocabulary was full of big words. But, then, kids love to use big words, and pick them up easily. Dr. Hans von Baeyer's wife, Bea, was the head of a preschool. She asked her husband to come in one morning to try out his pedagogical hypothesis.
He entered the classroom in the basement of a local church where his wife and all the kids were. Hans was carrying a couple of shopping bags. "Hey, kids, I understand that today we are to clean out Goldie's aquarium. Mark, why don't you come over here and start scooping water out and pouring into the drain in the floor right here." Mark worked hard for a little while but the water level didn't go down very much despite all the hard work.
"Look what I have in these bags: lots and lots of little hoses (actually laboratory grade rubber tubing). Maybe if we take one and put one end into the aquarium and the other end down by the drain, the water will go out all by itself." The hose was so arranged but no water came out. "What's wrong?" asked Hans.
Johnnie, a smart kid, yelled out, "You've gotta suck on the hose to get it started!" So Johnnie was asked to demonstrate and soon got the hose working despite getting a bit of Goldie's water in his face. After a brief "lecture" on how to get syphons going by needing to put a little effort in - termed "activation energy", it would then go on and on by itself.
"What about if we have a race? Say we take another hose and instead of just laying over the side of the aquarium, we loop it over the pipe up there near the ceiling." As Johnnie started sucking on the lower end, the other kids could see the water rise higher and higher in the semi-transparent tube until it got up to the pipe, and then it suddenly came flooding down, and the kids screamed to warn Johnnie to get out of the way! Now two tubes were draining water out of the aquarium. And, really to no one's surprise, Johnnie said it took a lot more "activation energy" to get the second one going.
Two kids then started counting the number of cupsfull in a minute that came out of the ends down by the drain. After a minute, it seemed both tubes were flowing at the same rate. So activation energy did not seem to affect the rate.
When the kids lifted the bottom ends of the tubes higher off the floor, they noticed a rapid drop in rate. And what really mattered was the vertical distance between the water level in the aquarium and the bottom, outlet end of the hose. They called this the free energy change of the reaction. The greater the free energy change, the greater the rate. (Later they found that a larger diameter hose would make it go faster also - BUT to get the larger hoses going took no more activation energy than it took to get smaller hoses going. What only mattered was the height.
One of the wayward kids was groping around in one of the bags and came up with a very, very long hose. They soon had that hose draped over chairs and tables, the teacher's shoulder, and the ceiling pipe. Johnnie again went to work sucking, and felt pretty sure that it was no harder to start than the one that went only over the ceiling pipe. So they learned that the activiation energy of a long chain of reactions was only equal to the highest peak in the chain. And the water flowed just about as fast as the other hoses of the same diameter.
A few days later, lots of moms and dads came to the preschool a little earlier than usual with their kids. A bus then took them all to Busch Gardens. They arrived nearly an hour before the gates opened for the public. All the kids and their parents plus the teacher and Hans, went to the roller coaster. After they were all strapped in, Hans radioed to release the brakes. The little train rolled forward a few yards and then stopped. "What happened?" shouted Hans. Almost in unison the little kids yelled "We've got to be activated!" Parents' mouths dropped open in surprise. "Well, how do we get activated?" "You've got to start that chain and it will pull us to the top."
Soon the train was looped over the top and stopped. "Does anyone notice anything?" asked Hans, precariously standing up in the middle car. Faces large and small looked all around. Finally one observent little one yelled: "We are at the highest point - like the water was when it was up at the pipe, and then it started flooding down." "What does that mean?" Hans asked hoping for two answers, which he got almost immediately. "We are fully activated." And "We should be able to go all the way to the end - just like with the super-long hose."
Hans sat down, called for the release the brake, and off they went with happy screams filling the air. But after a few loops, they couldn't quite make it to the top of a secondary "mountain." They rolled backwards and finally the train settled in a valley. Wondering why they didn't get to the end as predicted, the kids then got a lesson about friction - having felt lots of wind in their faces, and that wind slowed them down.
"So what are we going to do about it? How are we going to get back to the starting gate?" One kid then noticed the chain running up the hill in front and was interrupted by a classmate: "We've got to be activated again!"
Maybe those parents didn't remember this lesson in thermodynamics, but those kids still do! And, dear readers, these syphon and roller coaster stories are not analogies of activation and free energies, these stories are real examples of two aspects of the Laws of Thermodynamics. These are universal laws that apply to everything in the universe - from chemical reactions, to syphons, to roller coasters, to the placing of satellites in orbit to the intergalactic expansion - EVERYTHING. To paraphrase it in your gramp's words: "Ya don't git sumpin' fer nuttin'. Ya gotta work fer it!" Or to paraphrase it in your teacher's words: "You are not going to get good grades unless you work for them. You must study; you must do your homework. You've got to activate yourselves!"
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