3.3 Definitions & Notes
PHASE CHANGES
WORDS FOR DEFINITIONS YOU NEED ARE IN RED
Phase
change
Heat of
fusion
Heat of
vaporization
Endothermic
exothermic
vaporization
Evaporation
Vapor
pressure
condensation
sublimation
deposition
PHASE CHANGE: thermal energy (HEAT) is transferred to or from a substance that causes a
change in phase.
During a phase change the temperature of the substance does not change
A phase change is reversible ( can be undone or the substance can be returned to its
original state)
Phase change is a physical change, NOT A CHEMICAL CHANGE.
Why doesn’t temperature change during a phase change?
The thermal energy is consumed while breaking bonds.
EXAMPLES:
Ice absorbs heat to melt to liquid water.
Liquid water gives off heat and freezes.
TRANSITION: when a substance is moving from one phase to another it is in TRANSITION
As a verb “ A substance is transitioning” – changing.
EXO THERMIC: when heat is given off (Ex means – outside)
ENDO THERMRIC: when heat is taken in
