Mechanism whereby atoms combine to form molecules. The two pairs associated with covalent bonds (see chemical bond chemical bond, The asymmetrical shape of the molecule arises from a tendency of the four electron pairs in the valence shell of oxygen to arrange themselves symmetrically at the vertices of a tetrahedron around the oxygen nucleus. The atoms in the water molecule are arranged with the two H-O bonds at an angle of about 105° rather than on directly opposite sides of the oxygen atom. Many of the physical and chemical properties of water are due to its structure. For these reasons, water serves both as a heat-transfer medium (e.g., ice for cooling and steam for heating) and as a temperature regulator (the water in lakes and oceans helps regulate the climate). Click the link for more information. of water are all unusually high. Ratio of the change in heat energy of a unit mass of a substance to the change in temperature of the substance like its melting point or boiling point, the heat capacity is a characteristic of a substance. Click the link for more information. of fusion and of evaporation and the heat capacity heat capacity Latent heat, also called heat of transformation, is the heat given up or absorbed by a unit mass of a substance as it changes from a solid to a liquid, from a liquid to a gas, or the Heat change associated with a change of state or phase (see states of matter). Because of hydrogen bonding between water molecules, the latent heats latent heat, It expands greatly as it freezes as a consequence, ice is less dense than water and floats on it. Conversely, when water is cooled in this temperature range, it expands. When heated from 0☌, its melting point, to 4☌, it contracts and becomes more dense most other substances expand and become less dense when heated. Water has interesting thermal properties.
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Its polarity and ionization are both due to the high dielectric constant of water. Click the link for more information., OH −, and a hydronium ion, H 3O +. Positive and Negative Electric ChargesĪ neutral atom or group of atoms becomes an ion by gaining or losing one or more electrons or protons. Although completely pure water is a poor conductor of electricity, it is a much better conductor than most other pure liquids because of its self-ionization, i.e., the ability of two water molecules to react to form a hydroxide ion ion,Ītom or group of atoms having a net electric charge. Because water is a polar compound, it is a good solvent. It reacts with certain organic compounds to form a variety of products, e.g., alcohols from alkenes. It is chemically active, reacting with certain metals and metal oxides to form bases, and with certain oxides of nonmetals to form acids. Chemical and Physical PropertiesĬhemically, water is a compound of hydrogen and oxygen, having the formula H 2O.
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It is also an important component of the tissues of most other living things.
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Most of the living tissue of a human being is made up of water it constitutes about 92% of blood plasma, about 80% of muscle tissue, about 60% of red blood cells, and over half of most other tissues. It is present in varying amounts in the atmosphere. In solid form (ice) and liquid form it covers about 70% of the earth's surface. It is the most familiar and abundant liquid on earth. Water, odorless, tasteless, transparent liquid that is colorless in small amounts but exhibits a bluish tinge in large quantities.