Skip to main content

Osmolarity and Tonicity

This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.

State

Osmolarity measures a solution's total solute concentration; tonicity describes how that osmolarity, compared to a cell's, moves water into or out of it.

Show

A low-osmolarity solution holds more water relative to solute than a high-osmolarity one, so water moves toward the higher side.

Watch for

Osmolarity counts dissolved particles, not suspended cells — a cell-crowded solution can still read lower.