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The simple answer is that the crystalline structure of ice is less dense than the amorphous structure in water.
The reason has to do with the Hydrogen and Oxygen atoms.
Hydrogen tends to give away it's electron, and thus is considered electro-positive.
Oxygen tends to gain electrons, and is thus considered electro-negative.
Oxygen begins with 6 electrons in its outer shell. By sharing with two hydrogen atoms, it fills the shell with 8 electrons arranged in 4 pairs. Two of these pairs are shared with the hydrogen atoms, and two are unshared.
While you might think of water as having a straight linear planar shape (the two hydrogen atoms repelling each other), it actually ends up with a tetrahedron shape with the 4 corners in 3-D space being the electron pairs, two of which are associated with hydrogen atoms. Thus, it gets the bent shape that is often depicted in diagrams.
Now, the two hydrogen atoms (that are now electropositive) on the water molecule tend to be attracted to the electronegative unshared electron pairs on the oxygen atoms forming what are called Hydrogen Bonds.
In fact, the hydrogen atoms can actually jump from one oxygen to the other, forming different forms of water.
H3O+ <--> H2O <--> OH-
Which is essentially the basis for acid-base chemistry which hydrogen and water are central parts of.
As water cools, this dynamic ability to make and break multiple hydrogen bonds, or interact with multiple oxygen atoms, as well as having the hydrogen jumping from one molecule to another is hindered as it approaches a fixed crystal structure. And, at about 4°C, water reaches its maximum density. As it cools further, it starts expanding as it forms a fixed crystalline structure with essentially 2 hydrogen atoms making hydrogen bonds with each oxygen molecule, and otherwise forming a structure with the maximum distance between individual hydrogen atoms.
Thus, with a little hand waving.... as the ice forms, fewer hydrogen-oxygen interactions form, and the volume increases or the density decreases.
Once formed, ice behaves like other solids and contracts when it cools and expands when it is heated.
See the linked Wikipedia articles on Ice, Water, and sp3 orbital hybridization.
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∙ 13y ago
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What is unusual about solid water compared to solids of other materials?
ice
Ice float on top of water?
Ice float on water because the density is lower.
In which phase of water can the molecules of water flow over each other?
Ice can float on liquid water.
Which of the solids listed in table 4 will float on water?
Un-answerable because there is no 'table 4' displayed in this question. Please rephrase.
Do pieces of ice float in salt water?
I think that salty ice cube do float in water because ice bergs float it water and they're made of salty water. i think i depends on the density (Amount of salt) in the ice
Are there other solids besides ice and water that will float in the same liquid?
Oil/petroleum (gasoline?) will float on top of water as well.
Why dosent an ice cube float in air?
An ice cube is the frozen form of water, therefore being a solid, and since it is a solid, the force of gravity applies to it. So, like most other solids, it simply just drops down onto the ground. For anything to float it must have density lower than the medium in which it sits. The density of ice is greater than that of air, though it is lower than that of water. Hence ice does not float in air bur does float in water.
What is unusual about solid water compared to solids of other materials?
ice
Do ice float in water?
yes, ice does float in water. it will eventually melt and change into water.
Ice float on top of water?
Ice float on water because the density is lower.
Do ice cubes in water float or sink?
They float, as ice is less dense than water.
Which phase of water can the molecules of water flow over each other?
Ice can float on liquid water.
In which phase of water can the molecules of water flow over each other?
Ice can float on liquid water.
Why do ice cubes always float a the top of the glass of water?
Ice is less dense than water and will float on water.
Which of the solids listed in table 4 will float on water?
Un-answerable because there is no 'table 4' displayed in this question. Please rephrase.
Do pieces of ice float in salt water?
I think that salty ice cube do float in water because ice bergs float it water and they're made of salty water. i think i depends on the density (Amount of salt) in the ice
When does water float and why does it float?
Water floats when it is in the solid phase, called ice. Ice floats because the density of ice is less than the density of water.
