States of Matter

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States of Matter
I. Describing the States of Matter
A. Solids is the state of matter in which
materials have a definite shape and volume.
1. The word definite means that the shape and
volume of a solid will not change as you move it
from place to place.
2. The word definite does not mean that the shape
or volume can never change.
B. Liquids is the state of matter in which a
material has a definite volume but not a definite
shape.
1. A liquid always has the same shape as its
container.
2. Its volume however is the same in any
container.
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C. Gases Is the state of matter in which a
material has neither a definite shape or definite
volume.
1. A gas takes on the shape and volume of its
container.
2. Example The total volume of the helium in the
metal cylinders would be much less than the total
volume of the balloons that could be filled up by
that helium.
II. Why do materials have different states of
matter?
A. Kinetic energy is the energy an
object has due to its motion.
1. Kinetic theory of matter all particles of
matter are in constant motion.
2. Knowing this can help us begin to understand
why materials have different states of matter.
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B. Explaining the behavior of solids
1. A solid is made up of particles which vibrate
around a fixed or central position.
2. Particles do not swap positions in a solid.
Particle of a solid
A
B
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C. Explaining the behavior of liquids
1. A liquid is made up of particles which move
about and hit each other.
2. Particles can swap position in a liquid by
moving past each other.
B
A liquid particle
A
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D. Particles in a gas
1. A gas is made up of particles which move
about much more quickly than in a liquid and
often hit each other.
2. It is the particles colliding with the sides
of a container which cause the pressure.
A gas particle
A
B
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III. CHARACTERISTICS OF PHASE CHANGES
A. A phase change is the reversible
physical change that occurs when a substance
changes from one state of matter to another.
1. Melting, freezing, vaporization,
condensation, sublimation, and deposition are
six common phase changes.
B. Temperature and Phase Changes
1. The temperature of a substance does
not change during a phase change
2. When a solid changes to a liquid
a. At first the temperature rises as a
solid warms up.
b. At the melting point, the temperature
stops rising and remains the same until the
melting is complete.
c. The temperature will begin to rise
again.
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3. When a liquid changes to a solid
a. At first the temperature of the
liquid decreases.
b. At the freezing point, the
temperature will remain at that temperature
until all of the liquid freezes.
c. After the freezing is complete, the
temperature will begin to drop again.
4. The temperature at which a substance
freezes (its freezing point) is identical to the
temperature at which it melts (its melting
point).
5. When a liquid changes to a gas
a. The temperature keeps rising until it
reaches the boiling point.
b. The temperature then remains the
same until the boiling is complete.
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C. Energy and Phase Change
1. Energy is either absorbed or released
during a phase change.
a. Endothermic change - the system
absorbs energy from its surroundings.
Melting, vaporization, and
sublimation are all examples of endothermic
changes.
The amount of energy absorbed changes
from substance to substance.
b. Exothermic change the system
releases energy into its surroundings.
Freezing, deposition, and
condensation are examples of exothermic
reactions
The amount of energy released changes
from substance to substance.
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D. MELTING AND FREEZING
1. The arrangement of molecules in water
becomes less orderly as water melts and more
orderly as water freezes.
2. Melting
a. In ice, the attractions between water
molecules keep the molecules in fixed positions.
b. When ice is removed from the freezer,
heat flows from the air to the ice.
c. As the ice gains energy, the
molecules vibrate more quickly.
d. At the melting point of water some
molecules gain enough energy and move from
their fixed position.
e. When all of the molecules gain energy
melting is complete.
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2. Freezing
a. When liquid water is placed in a
freezer, energy flows from the water to the air
in the freezer.
b. This process is the reverse of the
melting process.
c. As the water loses energy, the
molecules vibrate less quickly.
d. At the freezing point of water some
molecules lose enough energy and move into
fixed positions.
e. When all of the molecules lose enough
energy freezing is complete.
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E. VAPORIZATION CONDENSATION
1. Vaporization is the phase change in
which a substance changes from a liquid into a
gas.
2. A substance must absorb energy in
order to change from a liquid to a gas.
3. There are 2 vaporization processes
a. Evaporation - is the process that
changes a substance form a liquid to a gas at
temperatures below the boiling point.
b. A vapor is the gaseous phase of a substance.
c. Vapor pressure is the pressure caused by the
collisions of vapor and the walls of the
container.
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b. Boiling - When vapor pressure becomes
equal to atmospheric pressure, water boils.
The temperature at which this happens
is the boiling point of water.
As temperature increases, water
molecules move faster and faster.
When the temperature reaches 100C,
some molecules below the surface have enough
kinetic energy to overcome the attraction of
neighboring molecules.
Because water vapor is less dense than
water, the bubbles rise to the surface.
c. The boiling point of a substance
depends on the atmospheric pressure.
At higher elevations the atmospheric
pressure is lower.
This will cause the boiling point to
occur at a lower temperature(which increases
cooking time).
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4. Condensation - is the phase change in
which a substance changes from a gas or vapor to
a liquid.
a. This process is responsible for the dew on
grass and the fog on bathroom mirrors.
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F. SUBLIMATION DEPOSITION
1. Sublimation - is the phase change in
which a substance changes from a solid to a gas
or vapor without changing to a liquid first.
a. Example, at room temperature, dry ice
can directly change from a solid to a colorless
gas.
2. Deposition - is the phase change that occurs
when a gas or vapor changes directly into a solid
without first changing to a liquid.
a. Deposition causes frost to form on
windows.
condensation, freezing and sublimation