My students and I have seen metal samples cooled to liquid nitrogen
temperature, and for all metals we tried (copper, aluminum, iron, and
lead) we saw a rapid boiling at the end, when we think the metal had
reached the same temperature as the liquid.
I've played around with the ideas of heat exchange, heat capacity and
thermal conductivity but have no satisfactory explanation for this
phenomenon.
Any enlightenment would be greatly appreciated.
Mike
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Mike Moloney, Physics & Optical Engineering Department
Rose-Hulman Inst of Tech, 812 877 8302
moloney@rose-hulman.edu http://www.rose-hulman.edu/~moloney