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Sour Acids and Bitter Bases



• To distinguish whether a substance is an acid or a base with different indicators,

• Observing color changes when different reagents are used in acid and base substances,

• To be able to rank the substances according to the scale of acidity and alkalinity,

• It is aimed to observe that we obtain a neutral solution (homogeneous mixture) as a result of the acid-base reaction


Curriculum alignments

• Cambridge Lower Secondary 

7Cp.02 Understand that the acidity or alkalinity of a substance is a chemical property and is measured by pH

7Cp.03 Use indicators (including Universal Indicator and litmus) to distinguish between acidic, alkaline and neutral solutions




Acids are materials that can release a proton and bases are materials that can accept a proton. This
tendency to release or accept a proton is measured based on the concentration of H and OH ions.
These characteristics can also be observed using additive substances called indicators which change
color based on the acidity / basicity of the environment. Cabbage juice is a natural indicator. In this
experiment, the change in color of cabbage juice when added to different substances is observed.
Furthermore, HCl and NaOH are used to conduct a titration and the change in acidity of the
environment is seen as change in the color of phenolphthalein indicator added to the solution.