One of my favorite tricks with liquid nitrogen (LN2) was to pour some onto a chalk tray at the bottom of a chalk board. The skittering, madly boiling liquid would entrain the chalk dust from the tray and transport it to the end where it would plummet to the floor making that wonderful muffled popping sound. The chalk dust would be splatted onto the floor where it would lie as a thin, mysterious white cake. I suspect the janitors were rather less delighted by this than I was.

Today’s youthful chemists, these tender shoots, probably think that dry erase white boards have been around since the time of the pilgrims. That’s OK.  I’ll not speak of squealing chalk, long leatherbound erasers, and chalk dessicated hands. The use of blackboards and chalk will remain our little secret.

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