TOW (& Answer)...

The question this week was what is efflorescence?  Efflorescence, to quote the source, “is the process in which a crystalline hydrated solid loses water of crystallization to the air.  A powdery deposit is gradually formed.”

The question (& answer) were taken from p. 85 of The Facts on File Dictionary of Chemistry by John Daintith.  The book was published by Checkmark Books in 1999.