A yellow curry stain on a white shirt turns reddish-brown when the shirt is scrubbed with soap, and turns yellow again after rinsing. Why?

Soap is an acid that changes the colour of turmericCorrect answerYour answerTurmeric is a natural indicator that turns reddish-brown in a basic solutionCorrect answerYour answerSoap bleaches the turmeric permanentlyCorrect answerYour answerThe water reacts with turmeric to make a new compoundCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

Soap solution is basic.
Turmeric is yellow in acidic or neutral conditions and reddish-brown in basic ones. Rinsing removes the soap, so the colour returns.

Worth noting

The colour change reverses, which shows it is an indicator effect, not bleaching.

Concept: Natural indicators
Typical timeTypical: 90 s
Your timeYours: —

The rule this testsAcids, bases and salts

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Ten questions from Everyday Chemistry, at your own pace.

A yellow curry stain on a white shirt turns reddish-brown when the shirt is scrubbed with soap, and turns yellow again after rinsing. Why?

Explanation