Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/17/84; site mhuxt.UUCP Path: utzoo!watmath!clyde!cbosgd!ihnp4!mhuxt!js2j From: js2j@mhuxt.UUCP (sonntag) Newsgroups: net.puzzle Subject: Re: Does the hole expand when heated? Message-ID: <1230@mhuxt.UUCP> Date: Wed, 30-Oct-85 16:29:20 EST Article-I.D.: mhuxt.1230 Posted: Wed Oct 30 16:29:20 1985 Date-Received: Sat, 2-Nov-85 01:29:17 EST References: <1114@decwrl.UUCP> Organization: AT&T Bell Laboratories, Murray Hill Lines: 39 > Does the hole expand when the metal around the hole is heated? > Try it for yourself! Here's how... > [This experiment is given in the 7th grade General Science book published > by D.C. Heath, 1961. I used it many times in my former junior high science > teaching days to prove that metal expands when heated.] > > You need 2 pieces of apparatus: > 1) loop of 1/4" thick metal, attached to a wooden handle so it can > be held in a flame without burning yourself. > 2) ball that just fits through the metal loop, attached to a wooden > handle so you can hold it easily. > > Procedure: Holding the loop by its handle, place the metal end in a flame > for a minute or so (We used a gas burner, but even a fireplace will > do). Then try to fit the ball apparatus through the loop. You > will find that the heated metal has expanded in all directions > (including inward into the space of the hole), making the hole smaller > so that the ball no longer fits through the loop. Once the loop cools > off, the ball will once again be able to fit through. This from someone who used to *teach* junior high science! Apparently it's been a long time since you tried this experiment. Try it again. Or use a Xerox machine which has scaling capabilities. Draw a circle on a piece of paper. Have the Xerox machine scale it to 160% (or whatever yours does easily). Is the inside of the circle bigger? Or did the line expand, making the inside of the circle smaller? Or consider a coin. Think of an arbitrary circle on the surface of the coin. Imaging heating the coin. The circular piece inside the circle expands, right? If the (imaginary) hole in the torus-like piece outside the circle got smaller, the coin would explode, wouldn't it? Do coins do that when heated? No? So the hole must expand too, right? Right. If I ever have a kid to send through school, I guess I'll have to be very wary of the quality of science teachers they get. We've just seen proof that some science 'teachers' are ignorant of the most basic concepts. -- Jeff Sonntag ihnp4!mhuxt!js2j "What would Captain Kirk say?"