Ice floats because it is less dense than water. Water has a density of 1.0 gm/cubic cm.
The density of ice Ih is 0.931 gm/cubic cm.
But, why is ice less dense than water if both are made up of molecules of H2O?
To Rotate the Molecule--->Left Click and Drag
To Zoom-->>Left Click + hold Shift button and Drag Vertically
Jsmol Menu --->>Right-Click
Change to wireframe first:
Click on right mouse button over box
Style --> Schemes --> wireframe
Style -->Label ---> atom number
Measure the following angles:
To measure angles: hold left mouse bottom over atom and double click on atom 1, drag to second atom (center atom) single click center atom, drag and double click atom 3.
Liquid water has a partially ordered structure in which hydrogen bonds are constantly being formed and breaking up.
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 molecules.
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 --
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:
Unlike ice -- water at room temperature is in constant motion -- hydrogen bonds are constantly formed and being broken-- click here to see water molecules in motion