Liquid water is "special"
in that it exhibits a high degree of order due to a network of hydrogen
bonds. This network readily adjusts to incorporate other molecules capable
of hydrogen bonding but "rejects" molecules where hydrogen
bonding cannot occur.
Build a "cluster" of water molecules. Click on
and select sp3 oxygen (a "water molecule"). Hold
down on the Insert key and click 30-40 times at different
locations on the screen. Rotate the structure every few "clicks"
to make certain that it is "three-dimensional". Don't "click"
too close to an existing water molecule (or you will make an OO bond).
Click on .
The resulting "water cluster" should be roughly spherical and
you should be able to identify numerous H2O - - -HOH
Replace one of the water molecules in the "middle" of your
cluster with an ammonia molecule. Select sp3 nitrogen from
the model kit and double click on the oxygen atom (not a free
valence) on the selected water molecule. Click on .
Only modest reorganization is required in order to accommodate the ammonia
molecule inside your cluster.
Replace the ammonia molecule by a methane molecule (select sp3
carbon from the model kit and double click on the nitrogen in
your structure). Click on .
Methane does not "fit" inside your cluster. The surrounding
water molecules spread out to give it room.