The water in the liquid state has the unenviable reputation of having abnormal properties. duke ldo

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The water in the liquid state has the unenviable reputation of having abnormal properties. duke ldoc The figure above describes an experiment conducted in October 1657 at the Accademia del Cimento (Academy of Experiment) in Florence. [1] This was the first scientific duke ldoc experiment to demonstrate the existence of a maximum density of liquid water at a slightly higher temperature (4 C) freezing, and a brutal expansion of water at its freezing. To conduct this experiment, academicians used a graduated glass tube 116 cm long with a bulb at its base to track the movement of water during the freezing process. The time was measured duke ldoc using a calibrated pendulum to perform 65 oscillations per minute. The experiment consisted of pouring liquid water in the tube and record in a table the level reached by the water on the measuring cup. This produced a qualified state of "natural." When the tube immersed in ice, there was a rise in the water level in the tube that were known due to a contraction of the glass due to cooling rather duke ldoc than an expansion of the water. To maintain a sufficiently low temperature is added to the alcohol and salt on the ice surrounding the tube. After this "leap after immersion," a third phase called "the fall" was observed corresponding to the slow descent of water in the cooled tube. The next step known as the "resting point" corresponded when academics no longer observed no change in the volume of water. Once past this stage, 'elevation' phase occurs during which we saw the water rise slowly in the tube. Then, suddenly, very surprisingly, duke ldoc there was the "leap freezing" marked by a rapid change in the volume of water which inevitably caused the breakup duke ldoc of the glass tube.
This surprising behavior of liquid water continues to be much written in the scientific literature, including today. Indeed, it implies duke ldoc that the ice floats on the water, or in other words the density of liquid is greater than the density of the solid. Indeed, it is expected a priori that it there is less of chemical bonds between atoms in the liquid duke ldoc that is highly thermal motion which allows the molecules to turn on themselves in the solid or movement rotation can not take place. As there are more links in the solid, so it is expected to lower volume occupied since the chemical bonds between atoms closer. It is precisely the opposite occurs in water below 4 C. The liquid seems, despite the molecular hubbub that reigns in this state, form more connections in the solid state where everything duke ldoc is tidy and orderly and the only allowed movement is an oscillation duke ldoc of atoms around a point Fixed. Incidentally, it is noted that it is thanks duke ldoc to this anomaly as a lake or ocean can deep freeze. Indeed, as it forms a layer of ice that floats on the liquid, and as the ice is a good thermal insulator, water under the ice remains liquid even if the outside duke ldoc temperature is extremely low. For the record, the absolute world record low temperature of -89 C in Antarctica and that of mainland France is -41 C.
For isotopomer H 2 O 16, the maximum density of ρ = 999.972 kg m -3 is observed to a temperature T = 3,984 C, while for D 2 O 16 is found ρ = 1105.3 kg m - 3 at T = 11.185 C and also ρ = 1112.49 kg m -3 at T = 4,211 C for isotopomer H 2 O 18. The simplest explanation of this phenomenon is the very special structure of the hexagonal ice that is based on a periodic stack of pentameric entities (H 2 O) {} H 2 O 4, which is that because of the existence duke ldoc of the hydrogen bond, each oxygen duke ldoc atom has exactly four neighbors. This constraint is that there is in the structure of many voids in the form of channels with a hexagonal structure. However, in a mesh network of hexagonal ice there are 4 molecules of water which have a volume of about 20 Å 3, so that the mat