Indicators change over a narrow pH range. Universal indicator is a mixture of indicators that changes over a wide range of pH, but as a result there is a continuous colour change, and so it is unsuitable for use in titrations. At "A" level, it is worth remembering two indicator examples. Methyl orange changes in the range pH 4-6, and is suitable for use with a strong acid and weak base (like ammonia and hydrochloric acid). It is orange-yellow in alkali and orange-red in acid. Phenolphthalein changes in the range pH 8-10, and is suitable for use with a weak acid and strong base (like ethanoic acid and sodium hydroxide). It is colourless in acid and pink in alkali. Either indicator can be used for strong acid/strong base titrations (like sodium hydroxide and hydrochloric acid). Weak acid-weak alkali titrations are generally not done as there is no clear end point.