insoluble

Everyday

1. (science) Not able to dissolve in a liquid, usually water: sand is insoluble in water. tree →
2. Impossible to solve or answer: an insoluble problem. tree →

In the lessons

In science lessons on materials and mixtures, pupils test whether substances are soluble (salt, sugar) or insoluble (sand, chalk, oil); insoluble solids can be separated by filtering. In maths and stories, an insoluble puzzle has no solution. Phrases: insoluble in water, insoluble problem.

Examples

• Sand is insoluble in water, so we can filter it out. tree →
• Salt is soluble, but chalk is insoluble. tree →
• Oil is insoluble in water and floats on top. tree →
• The mystery seemed insoluble until the detective found a clue. tree →
• Some maths puzzles are truly insoluble. tree →
• Insoluble fibre in food helps digestion. tree →

Note

Opposite: «soluble». In science, insoluble in water does not mean insoluble in everything: oil paint dissolves in white spirit. For problems, «unsolvable» is more common in everyday speech.