The cooling curve below represents the uniform cooling of a substance, starting at a temperature abo

January 2018 NY Regents Chemistry Exam

49 The cooling curve below represents the uniform cooling of a substance, starting at a temperature above its boiling point.

During which time interval does the substance exist as both a liquid and a solid?
(1) min2 to min4

(2) min4 to min5

(3) min5 to min7

(4) min7 to min9

Solution: The horizontal lines represent two phases together. In the cooling curve, we start with a gas (1-2min), then gas and liquid (2-6min), followed by liquid (6-7min), followed by liquid and solid (7-9mins) and finally only solid (9-11min).

Answer: 4

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