Why does ice float in water?

Answer 1

why does ice float? Like most things that float, ice floats because it is less dense than liquid water. Ice is about 9% less dense. When ice forms, it takes up about 9% more space than it did as a liquid. Thus, a 1 liter container of ice weighs less than a 1 liter container of liquid water, and the lighter material floats to the top. As I said, water is different

Keep in mind that Water is different. With most everything on Earth except freshwater, the colder it gets, the more dense it becomes. Take alcohol for instance. If we were to fill up a 1 liter container with pure alcohol at 30 degrees Celsius (86 Fahrenheit) and then take another 1 liter container and fill it with pure alcohol at 10 degrees Celsius (50 Fahrenheit) the cooler container of alcohol would weigh more. This is because the cooler alcohol is more dense, so more alcohol molecules can fit in the same container. This is true with freshwater too, up to a point. But at about 4 degrees Celsius (40 Fahrenheit) water reaches its densest point. Amazingly, as water cools further, it actually becomes less dense.

Answer 2

Like most things that float , ice floats because it is less dense than liquid water . Ice is about 9% less dense

Answer 3

I learned in Bio that water floats because of its density. Once the water molecules stop moving (because of the cold temp) there are little empty spaces in between the frozen water molecules so ice floats, letting life under water become possible. (water under wont freeze) And air is lighter than liquid water.
Hope that helped

Answer 4

The ice are float on water because its density less than that of water

Answer 5

Six water molecules in the solid state can orient themselves to form a regular hexagon. These molecules will form a rigid structure like molecules
do in solids. They will bond to each other by hydrogen bonding. However, in the liquid state the molecules will not form a regular, rigid hexagon. They
will bond to each other by hydrogen bonding and pack together.

The center of the hexagon has empty space. Water molecules in the solid phase occupy more space. i.e water(liquid) expands when it freezes and can break
its container if there is no room available for the frozen water to expand.
Solid H2O (ice) is less dense than liquid H2O (water). Ice will therefore float on water. Rivers never become completely frozen because as soon as
water freezes, it floats up to the surface. Fish live in the unfrozen, denser liquid water below the layer of ice.

Solid water (ice) floats on liquid water. This is the opposite of what you would expect. It would make sense that the solid form would sink because solids tend to be denser. The molecules in solids tend to have less kinetic energy than do the molecules in the liquid form. Therefore, the molecules in a solid will have more opportunity to be attracted to one and another, and therefore, they "group" closer together. Solids are typically more dense than their liquid counterpart, and therefore, sink when mixed with the liquid. This does not happen with water. This is because as the liquid water cools to near freezing (4 o C) the water’s density changes. At this point the molecules move very slowly and are attracted to each other. However, as they "group" together, they do so in an organized fashion. The "hydrogen bonds" that exist between the molecules, and the molecular shape of water itself, act together to make the water molecules bond in an organized hexagonal pattern. This is the most efficient way of "packaging" water molecules. When water "groups" into these hexagonal patterns, there is empty space between the molecules, which makes the frozen water to be less dense than the liquid form. In this case, because of the hexagonal pattern made as water freezes, its solid form takes up more space (less dense) than the liquid form. Thus, solid water floats on liquid water.

Answer 6

Ice has a density of slightly less than 1g/cm3 (the density of water). Since the ice is lighter than water, it floats.

Answer 7

When water is frozen it becomes less dense, therefore it will float on liquid water.

Answer 8

The popular answer is: "Ice is less dense than water."

This raises a question: Why is ice less dense than water?

It has to do with the structure of the water molecule: http://en.wikipedia.org/wiki/Image:Water_molecule.svg shows how two atoms of Hydrogen bond to one atom of Oxygen to from a molecule of water. The two hydrogen atoms from an angle of 104.5 degrees with the oxygen atom.

The size and shape of the water molecule stays the same regardls of whether the water is liquid, solid (ice) or gas( steam).
However the organization of the water molecules with respect to each other changes dramatically.

In a gas the molecules are moving quite fast, are a long way away from one another ( typically tens or hundreds of molecular diameters between molecules). In a liquid molecules are close to one another, essentially touching but free to move. In a solid the molecules are fixed with respect to one another, and don' move.
( or the vibrate a little bit, and only very rarely move enough to change positions in a process called diffusion.) The kinetic theory of temperature basically says temperature is a measure of molecular energy, or how fast the molecules move. Not moiving is a solid, moving slowly is a liquid and moving very fast is a gas. Another way to visualize this is think of a bunch of school children, out on the play gound they can run around, are quite far apart, and are like a gas. In the hallway they are free to move, but are closer together and because of their neighbors move more slowly and are like a liquid. In the classroom they all sit at their desks in ordered rows. They are expected to stay put and while they may wiggle in their seats they don't move far from their desk. This is like a solid.

Because of the shape of the water molecule when water freezes to become ice something very interesting happens. The Ice forms a heaxagonal crystal. See a picture at http://www.lsbu.ac.uk/water/images/ice1h4.gif.

The key point is that in this hexagonal structure of ice the water molecules are farther apart than they would be if they were in the liquid phase.

You can read more about the crystal structure of ice at http://www.lsbu.ac.uk/water/ice1h.html and http://www.its.caltech.edu/~atomic/snowcrystals/ice/ice.htm
These pages also talk about how ice froms different crystal structures when it freezes at different (very high) presures.

In addition to its shape the water moleucle has another property which causes the ice to form the hexagonal structure. In the Water molecule the Oxygen atom has a more negative charge and the two hydrongen attoms have slight positive charges. This means that when ice forms the Hydrogen atoms are attracted to the Oxygen atoms of a neighboring water molecule in the crystal. And so the water molecules pack together in a way that allows what is a called a hyrdogen bond to form between each Hydrogen atom and an oxygen atom that is in a different molecule.

A good picture is provided here.http://www.chem.tamu.edu/organic/Spring99/water.gif
which shows the bond dipoles and the dipole moment of the water molecule.

You can read more about the bond dipoles in water molecules at these pages:
http://www.chem1.com/acad/sci/aboutwater.html
http://www.science.uwaterloo.ca/~cchieh/cact/applychem/waterphys.html
http://www.chem.tamu.edu/organic/Spring99/dipolemoments.html

So, now you have an answer in terms of the molecular shape and molecular properties why ice floats on top of liquid water.

Answer 9

because ice has a lower density causing it to float on top

Answer 10

when water freezes it expands. Therefore less dense! Less dense than water floats on water. more dense sinks.
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