Density of Water - temperatures and the solid form does not...

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Density of Water Water is most dense at 4 degrees and as it warms, it becomes less dense due to increased molecular motion associated with temperature increases. Hydrogen bonds hold water molecules farther apart than they would be without the bonds. The normal motion of liquid water molecules causes some of the hydrogen bonds between water molecules to break, enabling them to become packed closer together. As water gets colder than 4 degrees C, there is less movement of the molecules and therefore less breaking of hydrogen bonds. Increased hydrogen bonding results in a greater average distance between water molecules. The water becomes less dense because a given volume contains fewer molecules. As ice forms, the number of hydrogen bonds becomes maximal (4 per water molecule) causing ice to be less dense than water. Ice floats on water because it is less dense than water. Other compounds are more dense at lower
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Unformatted text preview: temperatures and the solid form does not float on the liquid form. Ionization of Water We learned earlier that atoms that gain or lose electrons become ions. Hydrogen is the smallest atom, composed of one electron and one proton. It can lose its electron to become an ion. A hydrogen ion , however, is a proton because there are no remaining electrons. The words "proton" and "hydrogen ion" are often used interchangeably in discussion of biological topics. Within water, some of the molecules will temporarily lose a proton and leave the electron behind. The equation below describes this process. H 2 O ↔ H + + OH-When water ionizes, equal numbers of hydrogen ions and hydroxide ions (OH-) are formed. The hydrogen ion (H + ) attaches to another water molecule forming a hydronium ion (H 3 O + ). The process is reversible; hydrogen and hydroxide ions can combine to form water....
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