High School Chemistry : Help with Sublimation and Deposition

Study concepts, example questions & explanations for High School Chemistry

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Example Questions

Example Question #507 : High School Chemistry

The transition from a solid to a gas is known as __________.

Possible Answers:

deposition

evaporation

an impossible process

sublimation

Correct answer:

sublimation

Explanation:

Some substances will transition from a solid to a gas and skip the liquid phase entirely at standard conditions. This change from a solid to a gas is called sublimation. The reverse process of a gas going to a solid is known as deposition. As an example, solid carbon dioxide (dry ice) will sublimate to produce gaseous carbon dioxide at room temperature.

Evaporation is the process by which a liquid transitions to a gas.

Example Question #508 : High School Chemistry

Under which of the following conditions would ice be most likely to sublimate?

Possible Answers:

Low temperature and high pressure

High temperature and high pressure

Low temperature and low pressure

High temperature and low pressure

Correct answer:

High temperature and low pressure

Explanation:

Sublimation refers to the phase change whereby a substance goes directly from solid to gas. At high temperature and pressure water will be more likely to melt and than evaporate. At low temperature and low pressure, the water will likely stay solid. Likewise at low temperature and high pressure. At high temperature and low pressure, the ice will be most likely to sublimate. This is clear if one looks at the phase diagram for water. High pressure makes it energetically favorable for water to melt before evaporating. Keeping the pressure low, however, makes it more favorable to pass straight into the gaseous phase.

 

 

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