Red blood cells placed in distilled water swell and eventually burst. Distilled water is hypotonic relative to the cell, so water moves into the cells by osmosis, causing hemolysis.

Quick Scoop

  • What happens: The cells take in water, expand, and can lyse.
  • Why: Distilled water has a lower solute concentration than the red blood cell interior, so water moves inward.
  • Result: Hemoglobin leaks out, and the surrounding liquid can turn pink or red.

If you want, I can also explain this in one sentence for homework or in a diagram-style answer.