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Solvent Properties of Water

Water is an excellent solvent, but what does this mean? Solubility is the property of matter, a solute, to dissolve in a liquid. A solvent is a substance that dissolves a solute. But why is water so good at dissolving things?

At the top left is a water molecule, oxygen is represented as a red circle with the label delta negative, attached at the top are two white circles representing hydrogen, these are labeled delta positive. To the right is a cube filled with repeating large yellow and smaller blue spheres. This is labeled NaCl crystal. To the right of this is a key, a large yellow circle labeled chloride ion, with the symbol Cl negative inside. Underneath a smaller blue circle, labeled sodium ion with the symbol Na positive inside. Two arrows are drawn from the NaCl crystal. The one on the left points to water molecules surrounding the yellow chloride ion, with the hydrogen atoms pointing inwards with the labels delta positive. This is labeled hydrated chloride ion. To the right water molecules surround the blue sodium ion, with the oxygen atoms facing inwards with the labels delta negative. This is labeled hydrated sodium ion.

Figure 1: How water acts as a solvent.

Water is especially good at dissolving polar and charged molecules. As water has an uneven distribution of charge it is considered polar. One end of the molecule is slightly positive and the other negative. Water becomes heavily attracted to other polar molecules and ions. It forms hydration spheres around molecules and ions and breaks apart the attractive forces that hold solids like salts together dissolving them.