does ice float?
floats because it is less dense than water. Water
has a density of 1.0 gm/cubic cm.
density of ice Ih is 0.931 gm/cubic cm.
why is ice less dense than water if both are
made up of molecules of H2O?
about 3D molecules -- Our files on this page now
use Jsmol instead of Jmol. These files make use
on tablets, phones and easier use on Macs. For
the Jmol version of this page
click here. - Jsmol is best viewed with the
[Ice structure shown using
the JMol Applet]
Click the right mouse button with the cursor over
Style --> Schemes --> CPK Spacefill
Click on the left mouse button and rotate the ice
Do you see the open spaces in ice? They are formed
at low temperatures when water molecules form many
stable hydrogen bonds.
Compare this structure to that below of water
at room temperature.
Molecules are shown using the JMol Applet]
Style --> Schemes -->
Hydrogen bond lengths between water molecules will
vary since the molecules are in constant motion, unlike
ice which is a rigid lattice structure (above)
To measure distance
Double click on one atom then drag to second atom--
double click again
To measure angles
Double click on first atom, once on middle atom,
twice on atom three.
has a partially ordered structure in which hydrogen
bonds are constantly being formed and breaking
The strong hydrogen bonds give water a high cohesiveness
and, consequently, surface tension. This is evident when
small quantities of water are put onto a nonsoluble surface
and the water stays together as drops.
On the other hand ice has a rigid lattice
In liquid water each molecule is hydrogen
bonded to approximately 3.4 other water molecules.
In ice each each molecule is hydrogen bonded to 4 other
Compare the two structures below. Notice the empty spaces
within the ice structure.
In ice Ih, each water forms four hydrogen bonds with O---O
distances of 2.76 Angstroms to the nearest oxygen neighbor.
Because of ordered structure in ice there are less H20 molecules
in a given space of volume.
Try this --
1) Measure the O-O distances between any two
adjacent oxygen atoms in ice shown in the above structure..
Please enter your answer in
the space provided:
2) Measure the O-O-O angle formed
between adjacent oxygen atoms in ice.
3) What is the length of the hydrogen bond
H-O in ice?