Decreasing pressure effects

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cc609

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Would someone be able to explain this to me? How are different states of a substance affected with lowered pressure?

"If we decrease pressure while keeping temperature constant, three possibilities can happen. We can go from:

Solid to gas: Sublimation
Liquid to solid: Crystallization
Liquid to gas: Vaporization
"
 
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Temperature is constant but pressure is changing so pick a point and just move down and you will cross a phase change.

Just DECREASING not increasing you can go from solid-liquid solid-gas or liquid- gas

Whereas you would have to increase to do the reverse.
 
Would someone be able to explain this to me? How are different states of a substance affected with lowered pressure?

"If we decrease pressure while keeping temperature constant, three possibilities can happen. We can go from:

Solid to gas: Sublimation
Liquid to solid: Crystallization
Liquid to gas: Vaporization
"


Great question ! Different substances will indeed behave differently under different temperature and pressure conditions. Please refer to any General Chemistry text and look at a phase diagram. The diagram for CO2 and water will be perfect. You will see how different pressures affect these substances at a given temperature.

For the DAT exam, make sure you understand what phases are present during a pressure or temperature change.

This might help!
 

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