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I'm not an expert teacher or lecturer of chemistry. I was only a student from SMA NEGERI 15 SURABAYA who had been one of the Bronze Medalist Participants of Olimpiade Sains Nasional X (2011) of Chemistry In Manado, North Sulawesi, 11 - 16 September 2011 and graduated in 2012. Now, I'm studying at Universitas Airlangga in Surabaya, Indonesia. I do love chemistry and I would like to help them who had difficulties in studying chemistry. That's why, please understand me if you found some misconcepts in my entries. Suggestions are always necessary in order to develop this blog. And I'm sorry because my English isn't so well.

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Saturday, December 24, 2011

Christmas Day Special Topic: Water and Ice

(Source: http://www.davrodigital.co.uk/tutorials/snow-thumbnails/snow-scene.original.jpg)

Water. You're not a human if you don't know this compound. This matter brings us life, without this compound, Earth will be the same as earth: Empty, Dust, Dark, and Nothing but Rocks. Water, like another matter, has 3 normal phase: Solid, Liquid, and Gas. See the graph below:

(Source: http://serc.carleton.edu/images/research_education/equilibria/h2o_phase_diagram_-_color.v2.jpg)

1 mole of water consist of 6.02 x 1023 molecules of H2O. As we know that water has the Hydrogen Bond because of the big difference in electronegativity. This intermolecular interaction makes Water boils at 373 K at 1 atm. Without this interaction, water will boil at 173 K because of its "weaker" bond of polar covalent bond. God very loves us. Because of hydrogen bond, life goes on.

Water is a polar compound because of its unsymmetrical structure and lone pair of electrons. The geometry structure of water is V-Shape (sp3 Hybridization). Water is a very unique compound. It has anomalous: In the range between 273 - 277 K, if heated, water will be shrink and if cooled, water will be expand. Water can evaporate in any temperature. Water is a universal solvent because of its chemical characteristics. etc.

Water covers 70.9% of the Earth's surface, and is vital for all known forms of life. On Earth, 96.5% of the planet's water is found in oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation. Only 2.5% of the Earth's water is freshwater, and 98.8% of that water is in ice and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products.

Ice is water frozen into the solid state. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions. The addition of other materials such as soil may further alter the appearance. As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered a mineral. It possesses a regular crystalline structure based on the molecule of water, which consists of a single oxygen atom covalently bonded to two hydrogen atoms, or H-O-H. However, many of the physical properties of water and ice are controlled by the formation of hydrogen bonds between adjacent oxygen and hydrogen atoms. It is a weak bond, but is critical in controlling the structure of both water and ice.

An unusual property of ice frozen at atmospheric pressure is that the solid is approximately 8.3% less dense than liquid water. The density of ice is 0.9167 g/cm³ at 0 °C, whereas water has a density of 0.9998 g/cm³ at the same temperature. Liquid water is densest, essentially 1.00 g/cm³, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid. Density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm³ at −180 °C (93 K).

Further Reading . . .

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