•Defined shape
•Defined volume
•Fixed Particles
tightly packed
•Particles vibrate
in their places
•Defined volume
•Takes the shape of
the container
•Particles always
touching but
moving freely
•No defined shape
•Takes the volume
of its container
•Particles spread
out
•Particles move
rapidly and
bounce off each
other & walls of
container
Phase Changes in Matter
• A phase change is the reversible physical
change that occurs when a substance
changes from one state of matter to another.
• Energy is either
absorbed or
released during a
phase change.
Matter changes whenever energy
is added or taken away.
• When something is heated, it gains
thermal energy.
• When something is cooled, it loses or
transfers energy.
• Many physical & chemical changes involve
heating or cooling.
Law of Conservation of Energy
• States that “In EVERY physical or
chemical change, the total amount of
energy stays the same.”
• Remember: energy can change forms, but
energy can NEVER be created or lost.
Changes in Between Liquid and
Solid
• Melting and Freezing.
• Melting- change in state from solid to liquid,
energy is gained in this process.
• In most pure substances, melting occurs at a
temperature that’s specific to the substance,
called the melting point.
• Ex. Ice cube taken from the freezer. The
energy to melt it comes from the air in the
room.
Melting (solid → liquid)
• The added energy from the room’s air,
causes the water particles to move faster,
this raises the temperature.
• Then when the melting point is reached,
the water particles break free from their
fixed positions, temperature stops
increasing, and the particles arrange as a
liquid.
Freezing (Liquid → Solid)
• Changing state from a liquid to a solid.
• Involves loss or transfer of energy.
• Ex. Putting liquid water into the freezer.
The water loses or transfers heat to the
cold air inside the freezer.
• The water particles them move more
slowly, this means that the temperature is
dropping.
• The particles become closer together and
become fixed in position.
Changes in States Between Liquid &
Gas
• Vaporization (2 types: evaporation & boiling)
& Condensation.
• Vaporization- changing from a liquid to a gas.
• Evaporation- a type of vaporization that takes
place ONLY on the surface of the liquid.
• Ex. Of evaporation is a puddle drying up after
a rain.
• Evaporation happens because the energy the
particles gain from the ground, air, or sun
allow them to move faster, spread out, &
change to a gas.
Evaporation- a type of vaporization,
takes place ONLY on the surface of
liquid
Vaporization (Liquid → Gas)
• 2nd type of vaporization, is boiling.
• Boiling- takes place inside a liquid as
well as on the surface.
• Each liquid boils at a certain temperaturecalled the boiling point.
Condensation- (Gas → Liquid)
• Is the opposite of vaporization.
• Condensation is when a gas loses or
transfers enough thermal energy to become a
liquid.
• Ex. Breathing onto a mirror. Air from inside
you, transfers energy to the room and mirror.
The particles slow down, get closer and
arrange themselves as a liquid.
Changes in State Between Solid &
Gas
• Have you ever noticed how snow seems to
disappear even when the temperature stays
well below freezing? This is due to
sublimation.
• Sublimation- (Solid → Gas) occurs when
the surface particles of a solid gain enough
energy to become a gas, WITHOUT
becoming a liquid.
• Ex. Dry ice (solid carbon dioxide) gains
energy and turns directly into a gas.
Sublimation (Solid → Gas)
• Normal ice will also undergo sublimation.
• Ex. Ice left in an ice tray for a long time
gets smaller because the surface particles
gain enough energy to change into a gas.
• Where do you think the energy comes
from?