Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels.
Facebook Facebook Twitter Twitter. Updated February 03, Featured Video. Cite this Article Format. Helmenstine, Anne Marie, Ph. Ice and the Density of Water. What Are Examples of Hydrogen Bonding? How to Make Ice Spikes in your Freezer. What Is Buoyant Force? Origins, Principles, Formulas. However, the oxygen atom pulls on these negatively-charged electrons much more strongly than the hydrogen atoms can.
As a result, the electrons tend to hover closer to the oxygen atom than either of the hydrogen atoms. This leaves the molecule as a whole with a slight negative charge around the oxygen end, and a slight positive charge around the hydrogen end. Since opposites attract, the slight charges on different molecules interact with each other. In liquid form, as the molecules move around, hydrogen bonds form and break over and over, and the molecules can slip past each other. However, as the water cools down, it starts to form into its crystal lattice structure.
While the molecules want to form hydrogen bonds between the slight positive and negative charges, the same-charges repel each other, stopping the molecules from getting too close.
The result is a structure that is slightly less dense than liquid water. If you cool it further, it begins to expand again, and once it has completely solidified into ice, it has increased in volume by about 9 per cent. The bulk modulus of ice is around 8.
This means that if you seal a full container of water and freeze it, the pressure on the sides of the container will be approximately megapascals or , pounds per square inch.
The opposite is true in water. This property of water is somewhat unusual and rare. Density is defined as mass per unit volume of a substance. By saying that ice is less dense than water, we mean that a sample of ice will take up more space than a sample of water that has the same mass. At sufficiently cold temperatures, usually around 0 degrees Celsius 32 degrees Fahrenheit , water undergoes a phase transition to ice called freezing. This is because as the temperature becomes colder, the water molecules lose energy and move less.
The hydrogen bonds that form when water freezes into ice allow the molecules to be spaced farther apart, thus making them take more space, decreasing the overall density and making it float in the water. Its hydrogen bonds and its solid state actually make it lighter than it is as a liquid.
Water is an amazing substance that basically fuels life on earth— every living organism needs it. It also has some interesting properties that enable life to be the way that it is. Hot water and ice are both less dense than cool water. Less dense substances float on top of more dense substances. For example, when you make salad dressing oil floats on top of vinegar because it is less dense.
The same is true for everything. If you have a blow-up beach ball in a pool, it floats, if you have a rock, it sinks. The reason why ice is less dense than water has to do with hydrogen bonds. As you know, water is made up of one oxygen and two hydrogen atoms.
They are attached by covalent bonds that are very strong.
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