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Water


Water is an essential compound for all known forms of life on Earth to date, but not on another planet. Water covers nearly 71% of the Earth's surface. There are 1.4 billion cubic kilometers (330 million miles ³) is available on Earth. Water mostly found in the sea (salt water) and in the layers of ice (in polar and mountain tops), but can also present as clouds, rain, rivers, freshwater front, lake, water vapor, and sea ice . The water in these objects move follows a cycle of water: through evaporation, rain, and the water flow over the surface of the ground (runoff, including springs, rivers, estuaries) to the sea. Clean water is essential for human life.

In many places in the world there is a shortage of water supply. In addition to the Earth, a large amount of water is also estimated that there are at the north and south poles of Mars, as well as in the months of Europa and Enceladus. Water can be either solid (ice), liquid (water) and gas (water vapor). Water is the only substance which is naturally present on the surface of the Earth in his being the third. Water resources management can cause poor water shortages, monopolisation and privatization and even spark conflicts. Indonesia has laws governing water resources since 2004, namely Law No. 7 of 2004 on Water Resources

Chemical properties and physical

Water is a chemical substance with chemical formula H2O: one molecule of water is composed of two hydrogen atoms covalently bonded to one oxygen atom. Water is colorless, tasteless and odorless at standard conditions, ie at a pressure of 100 kPa (1 bar) and temperature of 273.15 K (0 ° C). This chemical is an important solvent, which has the ability to dissolve many other substances, such as salts, sugars, acids, some types of gas and many kinds of organic molecules.

The state of liquid water is a situation which is not common in normal conditions, especially with respect to the relationship between the other hydrides are similar in oxygen column on the periodic table, which suggests that water should be a gas, like hydrogen sulfide. Having regard to the periodic table, it appears that the elements surrounding oxygen is nitrogen, fluorine, and phosphorus, sulfur and chlorine. All of these elements when bonded to hydrogen will produce gas at normal temperature and pressure. The reason why hydrogen bond with oxygen to form berkeadaan liquid phase, is because oxygen is more electronegative than the other elements (except fluorine).

Pull the oxygen atom on the bonding electrons are much stronger than those carried by the hydrogen atoms, leaving the amount of positive charge on the two hydrogen atoms, and the amount of negative charge on the oxygen atom. There is a charge on each atom makes the water molecule has a dipole moment. Electric force of attraction between water molecules due to this dipole made of each molecule are close together, making it difficult to separate and ultimately raise the boiling point of water. Force of attraction is called a hydrogen bond.

Water is often referred to as the universal solvent because water dissolves many chemicals. Water is in dynamic equilibrium between the liquid and solid phases under standard pressure and temperature. In the form of ions, water can be described as a hydrogen ion (H +) associated (bound) with a hydroxide ion (OH-).

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