Definition

A chemical compound that is used as an indicator in acid-base reactions, turning red in basic solutions and colorless in acidic solutions. It was also used in the past as a laxative but is now considered toxic for that purpose.

Example

In the chemistry lab, we used phenolphthalein to determine the pH of the solution.

Conversation

Have you ever heard of phenolphthalein?

Yeah, it's that chemical used as an acid-base indicator, right?

Exactly! I learned about it in my chemistry class recently.

That's cool! It's interesting how it changes color in different pH levels.

Synonyms & Antonyms

Root Explanation

Phenolphthalein is formed from "pheno-" (from Greek "phainō", meaning to show or to appear) and "phthalein" (from Greek "phthaleinē", meaning to be made visible). The word refers to a compound that shows a color change, indicating the presence of acidity or alkalinity in a solution.

Memory Tip

Think of 'showing' ('pheno-') a color change when acidity is present — that's what phenolphthalein does.

Visually Confused Words