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HEAT & CONTRACTING WITH COLD
What is this business about expanding with heat and contracting with cold? Does anybody know?
Have any of you ever listened to the furnace at home, after it has finished running its' cycle? Hear it make sort of a ticking noise? What about when it first comes on and begins to heat? Ever hear it then? What causes those noises? Could it be the expansion and the contraction of the metal parts of the furnace?
We have some metal washers that are made of different materials. Some are steel, some are copper, and some are iron. Look at what a close fit they are when we drop them into this bottle. They just barely fit through the opening.
Now for the surprise. Or maybe it won't surprise anybody. Your most esteemed instructor will hold a washer (using pliers) over the flame and get it very hot, then put it into the bottle. HAH! Won't fit! Why not? Try one of another metal. It won't fit, either. And the next washer, of still another metal. Nope! Why won't they fit through the opening of the bottle?
Could it really be true? Does metal really get bigger when it is heated?
If we could get it hot enough, it would melt, and we could pour it in! We should find out just how hot each of these metals has to be in order to melt. Of course, we could not get any of them hot enough to melt. Unless we had a washer made of lead. Lead has a very low melting point--we learned that in another project, didn't we?
Well, we have to get those washers into that bottle. Maybe if we put them on ice for a little while, they would cool, and then fit through that bottle opening.
Let's try it.
Do you suppose...? No--couldn't be. That's too far out.
Well, let's talk about it anyway. After all, if scientists weren't curious about all things, they wouldn't be able to find out anything.
Do you suppose that big things, like steel bridges, railroad tracks, and concrete roads, have provisions for expansion and contraction? Do you suppose that those nice cracks in the sidewalks, and in roads, were put there so the slabs of concrete could expand when they got hot? Could it be that if they didn't have those grooves, and they got hot from the sun, that they would expand anyway, and break?
Do you suppose that steel bridges, and the rails on which the trains run, would buckle if the sun heated them and they expanded? Is that why train rails have gaps between the sections of rail where one section begins and the other ends? Is that why steel bridges have things that look like joints?
Has anybody ever watched a large building get started? They get a huge crane, and they put up the big steel beams. If you look closely at the beams, where they come together, it almost looks as though they don't quite fit. The reason for that is probably to give them room to expand and contract without breaking. Wow!
Cars. How about cars? The reason cars have radiators and water running about inside the engine is to keep the moving parts from getting too hot. If it gets that hot in there, it must get hot enough that the metals would expand. All those parts have to work together, but if they all touched, and then got hot and expanded, it seems that things would break. Having asked an expert, I have learned that they are put together with a little "clearance" (that means extra space), so the parts have room to expand. The clearance isn't too much, because when the car is cold, the parts would rattle before they were hot enough to expand. It must be difficult to build things so carefully.
If it snowed, and the concrete, the rails, or the steel bridges, got really cold, and they contracted (got a little smaller), do you think they would break?
That would be terrible! It is a good thing that science taught the building engineers about expansion and contraction.
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