Why do you think adding water (dilution) changes how acidic or basic the liquid is? Explain your thinking.

"Adding water to an acid or base will change its pH. Water is mostly water molecules so adding water to an acid or base reduces the concentration of ions in the solution. When an acidic solution is diluted with water the concentration of H + ions decreases and the pH of the solution increases towards 7."

Diluting an acid reduces the concentration of the H + ions that cause acidity, while diluting a base reduces the concentration of the OH - ions that cause basicity.

Explanation:

The pH scale covers a range between 0 and 14 pH. A pH of exactly 7 is neutral. pH values greater than 7 are basic, while pH values less than 7 are acidic. The pH scale is logarithmic with a base of 10, meaning each integer pH value is 10 times more acidic or basic than the one preceding or succeeding it respectively. For dilution to decrease the acidity or basicity of a solution, the solvent being used must be less acidic or basic than this solution.

Alternatively, an acidic diluent may be used to dilute a basic solution, or vice versa, in a neutralization reaction. Because of the logarithmic nature of the pH scale, diluting a strong acid or base even slightly causes its respective pH to rise or drop considerably. Weak acids and bases with pH values close to 7 are correspondingly not as affected by dilution.