Transcript Slide 1

1)
2)
What is Kinetic Theory of
Matter?
What is involved when matter
changes from one state to
another?
 Kinetic theory of matter states:
• All matter is made of atoms and molecules that act like
tiny particles.
• These tiny particles are always in motion. The higher the
temperature of the substance, the faster the particles
move, and the more they separate.
• At the same temperature, more-massive (heavier)
particles move slower than less-massive (lighter)
particles.
 Phase
change – occurs when a substance
changes its state of matter (gas, solid or
liquid)
• During a phase changes the temperature of a
substance remains constant and it exchanges energy
with it surroundings.
• Endothermic Reaction – such as melting or
vaporization (boiling), the substance absorbs energy
• Exothermic Reaction – substance releases energy to
its surroundings, like in freezing or condensation.
Heat Curves – are graphs that
show the relationship between
the change in energy levels to
the temperature of the matter.
1) Sketch the hurt curve on
your paper. Label where
the substance is solid,
liquid and gas. Label
where melting, freezing,
vaporization, and
condensation are
occurring.
2) Does the temperature
changing during a
phase change?
3) Does the amount of heat
added change during a
phase change? Why?
Heat Added

For problem 1, compare your answers to the heat curve for water.
Freezing occurs at the same place as melting. Condensation
occurs at the same place as vaporization.
#2 No
#3 Yes. It takes
more energy to
complete a phase
change because
molecular bonds
to be broken or
reformed.
1)
Which describes the process of the forming of water
vapor?
A. At the heat of vaporization point, absorbed thermal
energy changes water from a gaseous state to a solid
state.
B. At the heat of fusion point, released energy changes
water from a gaseous state to a solid state.
C. At the heat of fusion point, released energy changes
water from a liquid state to a solid state.
D. At the heat of vaporization point, absorbed energy
changes water from a liquid state to a gaseous state.
Answer: D
2)
Based on the energy changes that occur
when materials change state, determine
how water freezing on the fruit can
protect it from becoming too cold?
Answer: The process of freezing is
exothermic, so heat is generated as
water changes from the liquid to the
solid state. This heat protects the tree as
the water freezes on it.
From 20 to 60 oC, what is
happening on the graph?
Energy
Answer: C
a. The water has used up
the added energy.
b. The water molecules
have no kinetic energy.
c. The water molecules
kinetic energy is
increasing
d. The water molecules
kinetic energy is
decreasing.