What does dissociate in water mean and how does it affect acids and bases?

The word "dissociate" means to break up into ions. For example, with sodium chloride dissociates it forms Na+ and Cl- ions.

When acids dissociate, they break apart in the following manner: ##HA -> H^+ + A^-## Where H+ is the acidic hydrogen and A- is the rest of the acid (in anion form).

When bases dissociate they break apart in the following manner: ##BOH -> B^+ + OH^-## Where has positive charge and OH- is the basic hydroxide.

OK.

Good presentation, elegant font here: http://ibchem.com/IB/ibnotes/08.3.htm