found this...important points highlighted:
The Simple Definition
pH is a logarithmic measure of hydrogen ion concentration.
According to the Compact Oxford English Dictionary, the "p" stands for the German word for "power",
potenz,
so pH is an abbreviation for "power of hydrogen".
The hydrogen ion concentration in pure water around room temperature is about 1.0 × 10-7 M. A pH of 7 is considered "neutral", because the concentration of hydrogen ions is exactly equal to the concentration of hydroxide (OH-) ions produced by dissociation of the water.
Increasing the concentration of hydrogen ions above 1.0 × 10-7 M produces a solution with a pH of less than 7, and the solution is considered "acidic". Decreasing the concentration below 1.0 × 10-7 M produces a solution with a pH above 7, and the solution is considered "alkaline" or "basic".
An ion is an atom or group of atoms which have lost or gained one or more electrons, making them negatively or positively charged.
Ions are essential to life. Sodium, potassium, calcium and other ions play an important role in the cells of living organisms, particularly in cell membranes. They have many practical, everyday applications in items such as smoke detectors, and are also finding use in unconventional technologies such as ion engines. Inorganic dissolved ions are a component of total dissolved solids, an indicator of water quality in widespread use.
Self-ionization is the process that determines the pH of water. As temperature increases, hot water has a higher concentration of hydronium than cold water (and hence lower pH), but this does not mean it is more acidic, as the hydroxide concentration is also higher by the same amount.
Geissler have determined that electric field fluctuations in liquid water cause molecular dissociation. They propose the following sequence of events: the system begins in a neutral state;
random fluctuations in molecular motions occasionally produce an electric field strong enough to break an oxygen-hydrogen bond, resulting in a hydroxide (OH−
and hydronium ion (H3O+); the proton of the hydronium ion travels along water molecules by the Grotthuss mechanism; and a change in the hydrogen bond network in the solvent isolates the two ions, which are stabilized by solvation.
**********
So, change is the natural state of things. Water self ionizes (turns negative or positive) because of the presence of the chemicals in it, due to electrical field fluxuations and the natural properties of chemicals. That is a gross simplification, but I only had an hour on the net to figure this out.
