In a free expansion of ideal gas (into vacuum), the temperature:
AStays the same
BBecomes zero
CDecreases
DIncreases
Answer & Solution
Correct answer: A. Stays the same
Free expansion: no work done (against vacuum), no heat exchange (rapid). So ΔU = 0. For ideal gas, ΔU = 0 implies ΔT = 0 — temperature unchanged. (Real gases show Joule-Thomson effects.)
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