“Matter & Energy”
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2.
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Objectives:
Use the kinetic theory to describe the
properties and structures of the different
states of matter.
Describe energy transfers involved in
changes of state.
Describe the laws of conservation of
mass and conservation of energy, and
explain how they apply to changes of
state.
Why can you smell cookies baking in a
bakery when you are far from the oven?
Reasons…
1st: Assume that particles (atoms &
molecules) within substances can move.
2nd: Assume that the atoms & molecules
move faster as the temperature rises.
3rd: Energy moves from the oven to the
cookies, causing molecules in the cookie
dough to move fast & become gases
which spread out.
Kinetic Theory
All matter is made of atoms & molecules
that act like tiny particles.
 Tiny particles are in constant motion.
Higher temp. faster the movement.
 At the same temperature, more massive
(heavier) particles move slower than less
massive (lighter) particles.

Fluids
Solids:
 Rigid structure
 Fixed volume and shape
 Strong attractions of particles = vibrate
Liquids:
 Definite volume
 No specific shape
 Particles flow = easily slide
Viscosity: The resistance of a fluid to flow.
(The higher the attraction of the particles, the slower
fluid will flow.)
** both liquids and gases are fluids!!
Gases:
 Particles are far apart & move randomly
 No fixed volume or shape
 Gases can exert pressure
Why does a balloon with helium go
“flat” faster than a balloon filled with
air?
The wall of the balloon has
tiny holes through which
gas particles can escape.
The helium particles are
smaller & less massive than
the nitrogen & oxygen
particles found in the air.
The smaller & less massive
particles move faster, so
they get through the holes
more quickly.
What is the role of energy?
Demonstration (2 volunteers)
1) Dip one index finger into the water. Dip
your other index finger into the oil. Wave
each finger in the air.
2) Do your fingers feel cool?
3) Which liquid evaporated faster?
4) Repeat experiment using water on one
finger and rubbing alcohol on the other.
What happened??

Which of the three liquids evaporated the
fastest? Slowest?
 Which liquid cools the skin the most? Least?
The molecules in each liquid absorb energy from
their surroundings (skin) increasing the speed of
molecules. Alcohol requires the least energy to
escape from liquid. Oil requires the most!!
Energy’s Role
Energy: The ability to change or move
matter.
The Changes of State for Water
Evaporation: The change of a substance
from a liquid to a gas = cooling process
 Condensation: The change of a
substance from a gas to a liquid = heating
process: (must have a surface for it to
condense on!!!)
 Sublimation: The change of a substance
from a solid to a gas.
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Changes of State for Water
Examples
Evaporation = liquid to gas
 ex: sweat
Condensation gas to liquid
 ex: cold can of pop sweats
Sublimation = solid to gas
 ex: Dry Ice: Directly from solid to gas
What is the ENERGY doing?
ENERGY?
1.
2.
Sublimation
Boiling or
Evaporation
Melting
Freezing
ENERGY?
1.
2.
Gas
Liquid
Solid
Condensation
ENERGY?
1.
2.
Law of Conservation of Matter
Law of Conservation of Energy
Mass cannot be created or destroyed
(Matter can change from one form to
another but the total mass stays the
same.)
 Energy cannot be created or destroyed
(Energy can be changed from one form
into another but total amount stays the
same.)

Were You Paying Attention?
Define energy
 State the Law of Conservation of Energy
and the Law of Conservation of Mass.
 List two examples for each of the three
common states of matter.
 Rank the following in order of increasing
strength of forces between molecules.
a. Honey
b. Marble
c. Water
d. Nitrogen Gas
e. Candle Wax

Continued….


Compare and contrast the shape and
volume of solids, liquids, and gases.
Predict which two of the following involve
the same energy transfer. Assume that
the same substance and the same mass
is involved in all four processes:
a. Melting
b. Sublimation
c. Evaporation
d. Condensation
Continued
 Describe
the energy transfers that occur
when ice melts and water vapor
condenses to form liquid water.