What is the only physical difference between heavy water and pure water?

heavy water has greater density
heavy water is radioactive
heavy water is not translucent
heavy water conducts electricity
Heavy water contains deuterium instead of common hydrogen-1. In its pure form it has a density about 11% greater than water, but otherwise, it is physically and chemically similar. It is not radioactive. Because of greater density and stronger hydrogen-oxygen bonds, its behavior is slightly different in some biochemical reactions. It may be toxic, but only when a large fraction of water (> 50%) in higher organisms is replaced by heavy water.
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