acids increase the hydrogen ion concentration, which provides more ions
an acid comes in contact with a metal, the acid steals free electrons away. That loosens the bonds holding metal atoms in place, so the metal dissolves. That's a chemical change, so the ability of acids to dissolve metals is a chemical property
When a strong acid is neutralized by a strong base there are no excess hydrogen ions left in the solution. The solution is said to be neutral as it is neither acidic nor alkaline. The pH of such a solution is close to a value of 7; the exact pH value is dependent on the temperature of the solution.
