Indicator
A dye that changes colour depending on whether a solution is acidic or alkaline. Universal indicator gives a range of colours that match the pH.
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Analogy
It works like a traffic light for acids: red for acid, green for neutral, purple for strongly alkaline.
Example
Red/orange: acidGreen: neutralBlue/purple: alkali
In practice
Litmus paper turns red in acid and blue in alkali.
Practice
Flashcards
- What colour is litmus in acid and in alkali?Red in acid and blue in alkali.
Questions people ask
What is the difference between litmus and universal indicator?
Litmus has only two colours: red for acid and blue for alkali. It says which side of 7 you are on. Universal indicator is a mixture of dyes that goes through many colours, so it also shows roughly how strong the acid or alkali is.
Which indicator is best for a titration?
One with a sharp colour change at the end point, such as methyl orange or phenolphthalein. Universal indicator changes gradually through many colours and is hard to judge exactly. A single sharp change lets you tell the moment the acid and alkali have neutralised.