EXERCISE 10


  (a) Examine the borderline between the solid and liquid
      phases of the two molecules.  As pressure increases
      along each line, does the temperature increase or
      decrease?
  (b) Imagine a block of water ice on the ground in front of
      you on a below-freezing winter day.  If you place a 
      second block of water ice the same size on top of the
      first block, is that first block more or less likely
      than the second block to melt?  Explain.
  (c) Imagine a block of dry ice - that is, frozen carbon
      dioxide - one on the floor of a sealed, refrigerated room
      where the pressure is 10 atmospheres.  If a second
      block of the same size is placed on top of the first
      block, is that first block more or less likely than the
      second block to melt?  Again, explain.