Natural Science CLEP Prep Practice Exam

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Prepare for the CLEP Natural Science Exam with our comprehensive study materials and practice questions. Test your knowledge and ace the exam by mastering key concepts.

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What is the name of the phenomenon in which a gas cools when it is allowed to expand in a vacuum?

Sublimation
Adiabatic cooling
Condensation
Evaporation

The correct answer is: Adiabatic cooling

Adiabatic cooling is the term used to describe the phenomenon in which a gas cools when it is allowed to expand in a vacuum. This occurs because when the gas is allowed to expand, it has to do work in order to fill the larger volume. This work requires energy, which is taken from the gas, causing its temperature to decrease. Sublimation, condensation, and evaporation are not the correct answers because they do not involve the expansion of a gas in a vacuum. Sublimation is the process of a solid turning into a gas without going through the liquid state. Condensation is the process of a gas turning into a liquid. Evaporation is the process of a liquid turning into a gas. None of these processes involve a vacuum or the expansion of a gas.