By Mary Tarsi | Updated Mar 24, 2022
An egg will lose volume when placed in a solution with a higher solute concentration than inside the egg. In such a solution, the solvent (water) moves out of the egg by osmosis, causing the egg to shrink. The phenomenon demonstrates the basic principle of cellular water balance.
First, dissolve the shell with vinegar. The acetic acid reacts with the calcium carbonate, leaving the egg’s semipermeable membrane intact.
Submerge the shell‑free egg in a homogeneous mixture—e.g., water, corn syrup, or honey. The solution’s solute concentration dictates the direction of water movement.
Osmosis is the passive flow of water across a semipermeable membrane from an area of lower solute concentration to one of higher concentration, aiming to equalize concentrations on both sides. When the external solution is hypertonic (higher solute concentration), water exits the egg, causing shrinkage. If the solution is hypotonic, the egg swells. An isotonic solution keeps the egg unchanged.
Only small molecules like water can cross the membrane; larger solute molecules (e.g., sugar in corn syrup) are excluded. This selective permeability is why the egg can shrink in sugary solutions.
In educational settings, this experiment offers a hands‑on illustration of osmosis and membrane permeability.
