Page 12 - Surviving Chemistry BFF Homework Helper and Test Prep Preview

A phase change is a physical change.
Particles (atoms or molecules) rearrange, but are not
changed.

Energy is absorbed or released during a phase change.
Temperature of the substance stays the same (constant).

• A process that releases heat

Examples: Freezing, condensation and deposition

• A process that absorbs heat

Examples: Melting, evaporation and sublimation

• Liquid to solid phase change
Exothermic (heat is released)
Au(l) Au(s)

• Solid to liquid phase change

Endothermic (heat is absorbed) Au(s) Au(l)

• Gas to liquid phase change

Exothermic (heat is released) H 2O(g) H 2O(l)

• Liquid to gas phase change

Endothermic (heat is absorbed) H 2O(l) H 2O(g)

• Gas to solid phase change
Exothermic (heat is released) CO2(g) CO2(s)

• Solid to gas phase change

Endothermic (heat is absorbed) CO 2(s) CO 2(g)

Iodine (I2) solid and carbon dioxide (CO2) solid

are two substances that readily sublime at STP.

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