Experiment 7 — Acid, Base or Neutral?

Topic: Chemistry · Classes 6–7 · Acids, bases and indicators; neutralisation

Aim: Find out whether the mystery liquid (soap solution) is an acid or a base — then neutralise it.

Daily: Antacid tablets neutralise the excess acid that causes stomach pain. Curd is acidic, soap is basic, and farmers add lime to acidic soil. Turmeric on a white kurta turning red where soap touches it is this very experiment.

Red: The red litmus turned blue

Turmeric: The turmeric paper turned red

China: The china rose solution turned green

Question: You dip blue litmus paper in soap solution. What will you see?

Exp: Blue litmus only changes in acid. For a base you need red litmus or turmeric.

Question: Red litmus turns blue in…

Exp: That is the standard test for a base.

Question: Turmeric turns red when it meets…

Exp: Which is why a turmeric stain reddens where soap touches it.

Question: An acid plus a base in the right amounts gives…

Exp: That reaction is neutralisation.

Question: An antacid works because it is…

Exp: It neutralises excess acid in the stomach.