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        riddles >> easy >> Shrinking While Heated (Physics)
        
(Message started by: Barukh on Jul 4^th, 2005, 9:10am)

Title: Shrinking While Heated (Physics)
Post by Barukh on Jul 4^th, 2005, 9:10am

Is it possible that a solid substance shrinks when its temperarture rises? Assume there is no change in pressure.

Title: Re: Shrinking While Heated (Physics)
Post by JocK on Jul 4^th, 2005, 10:05am

the answer is [hide]yes (see e.g. http://physics.ucsc.edu/research/zs.html)[/hide].

Title: Re: Shrinking While Heated (Physics)
Post by baddab457 on Jul 4^th, 2005, 5:14pm

shrink wrap.. ;D

Title: Re: Shrinking While Heated (Physics)
Post by Bob Purcell on Jul 5^th, 2005, 7:25pm

Ice

Rap

Title: Re: Shrinking While Heated (Physics)
Post by Noke Lieu on Jul 5^th, 2005, 7:52pm

A steak on the barbie. :D

But there would be a difference in the turgour pressure of the cells. :(

And the pressure from your peers to cook it perfectly, but without being seen to fuss over it 8)

Title: Re: Shrinking While Heated (Physics)
Post by JocK on Jul 6^th, 2005, 10:07am

on 07/05/05 at 19:25:03, Bob Purcell wrote:

Ice

Rap

Don't think that is correct. Ice has a positive thermal expansion coefficient.

Now, if you allow for a phase transition (from ice into water) or simply consider liquified ice (water in the temperature interval of 0-4 degC), you will observe negative thermal expansion. The question, however, asks us to restrict ourselves to solids.

Title: Re: Shrinking While Heated (Physics)
Post by SWF on Jul 6^th, 2005, 7:40pm

Starting at a low enough temperature silica will shrink when heated. Zirconia shows a sudden volume decrease at an elevated temperature due to a (solid state) phase change, as do other solids. The alloy Invar (64 Fe-36 Ni) has near zero, and possibly slightly negative, thermal expansion over a fairly wide range of temperature. Graphite fibers often have negative thermal expansion along the axis of the fiber.

Related to this topic: one of the Maxwell thermodynamic relations says that derivative of volume with respect to temperature at constant pressure equals the negative of the derivative of entropy with respect to pressure at constant temperature.

Title: Re: Shrinking While Heated (Physics)
Post by Barukh on Jul 6^th, 2005, 11:48pm

Wow! So many interesting examples from JocK and SWF!

When asking this question, I was aware just of a single example - a certain crystallographic phase of pure plutonium. Look here (http://hypertextbook.com/physics/thermal/expansion/) for the nice graphs.

SWF, could you please provide references for your examples?