28 terms

Changes of State

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Changes between solid and liquid
melting and freezing
melting
state of change from a solid to a liquid
melting point of water
100 degrees C
At its melting point the particles of a solid substance are
vibrating so that they break from their fixed position
freezing
change of state from liquid to a solid; reverse of melting
at its freezing temperature the particles of a liquid are moving so
slowly that they begin to form regular patterns
freezing point of water
0 degrees C
Changes between liquid and gas
evaporation and boiling and boiling point and condensation
vaporization
change from a liquid to a gas
vaporization takes place when
the particles in a liquid gain enough energy to form a gas
evaporation is when
vaporization takes place only at the surface of a liquid
example of evaporation
shrinking puddle
boiling
occurs when a liquid changes to a gas below the surface as well as at the surface (another form of vaporization)
temperature at which a liquid boils is its
boiling point
boiling point depends on
the pressure of air above it
the lower the pressure,
the less energy needed for the particles of the liquid to escape into the air
places close to sea level the boiling point is
100 degrees C
places above sea level have a boiling point that is
lower than 100 degrees C
(example: Denver, CO the elevation is 1600 meters above sea level so water boils at 95 degrees C
Condensation is the opposite of
vaporization
condensation occurs when
particles in a gas lose enough thermal energy to form a liquid
water vapor is a
colorless gas that is impossible to see
Clouds, fog and steam are not water vapor, they are
tiny droplets of water suspended in air
sublimation occurs when the
surface particles of a solid gain enough energy that they form a gas (changes between solid and gas)
as they form as gas, particles
do not pass through the liquid state
examples of sublimation
dry ice or solid carbon dioxide
(at ordinary atmospheric pressure it cannot exist as a liquid)
carbon dioxide absorbs
thermal energy as it changes state (this property keeps materials near dry ice cold and dry)
when dry ice becomes a gas it cools
water vapor in the nearby air
when dry ice becomes a gas the water vapor
condenses into a liquid, forming fog around the dry ice
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