The remaining particle is a hydroxl ion. Micromolecules with different charges than water can cause ionization to happen as well. This dissociation process involves only a few water molecules at once. Strong acids, such as hydrochloric, dissociate almost entirely in water. Bases are molecules that take up these extra hydrogen ions.
Water passes through pores easily.
These are exactly the right size that water can get through them, while larger particles are held inside. This process is caused by a fluid attempting to seek equilibrium by going from a high pressure situation into a lower pressure one. This pressure that causes this operation is known as osmotic pressure. Another interesting state that water can be in is that of an isotonic solution. These are solutions which neither water is neither gained nor lost, and the pressure is equal on both sides of the cell membrane.