Question

Sara left a small amount of colorless liquid in a cup in the sun. A few hours later, she observed that the liquid was gone, but a white residue remained in the cup. Sara’s observations indicate the colorless liquid was?

A. Water
B. Salt solution
C. Sugar solution
D. Alcohol

Answer 1

The liquid that Sara observed to leave a white residue after evaporation was likely a salt solution, as salt remains as a solid residue after the water evaporates.

Step-by-step explanation:

Sara left a small amount of colorless liquid in a cup in the sun, and the liquid evaporated leaving a white residue. This observation indicates that the colorless liquid was likely a salt solution. When water evaporates from a salt solution, the water molecules enter the air as gas, leaving the salt behind as a solid residue. Hence, the correct answer is B. Salt solution. If the liquid had been pure water (A), no residue would remain after evaporation. A sugar solution (C) could also leave a residue, but typically sugar residues are more of a crystalline or sticky substance rather than just white. Alcohol (D) would evaporate completely without leaving any residue as it does not contain non-volatile solutes.