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Section 2.3
The Kinetic Theory
(pg. 476-‐480)
OBJECTIVES:
• Explain the kinetic theory of matter
• Describe particle movement in the 4 states of
matter.
• Explain particle behavior at the melting and
boiling points.
Vocabulary:
• Kinetic theory • Melting point
• Boiling point
• Solid
• Liquid
• gas
• Plasma
• diffusion
What states of matter are present?
• SOLID: veggies, pot,
• LIQUID: soup itself
• GAS: steam off soup
Kinetic Theory:
• An explanation of how
particles in matter behave.
Kinetic Theory’s Explanation: 1. All matter is composed of small
particles (atoms, molecules, and ions).
2. These particles are in constant, random
motion.
3. These particles are colliding with each
other and the walls of their container.
Picture it….
Keep in mind….
• As atoms are bumping into each other they
are transferring energy.
• The more energy they have, the faster they
move, the faster they bump into others
• Increasing the temp of a material increases
the movement of its atoms.
• Take out a sheet of paper please…..
• Fold a sheet of paper in half lengthwise.
Make the back edge about 5 cm longer
than the front edge.
• Turn the paper so the fold is on the
bottom. Then fold it into thirds.
• Unfold and cut only the top layer
along both folds to make three tabs.
Label the Foldable as shown.
SOLIDS
Characteristics of a SOLID
• Has a definite shape all its own
• Can be weighed in grams
• Can be counted
• Molecules are tightly packed
together-‐ can’t escape
LIQUIDS
Characteristics of LIQUIDS • No definite shape
• Does have a definite volume
• Can measure volume
• Can flow
• Particles are moving freely enough to
slip out of ordered arrangement
GASES
Characteristics of GASES • No definite shape
• No definite volume
• Can flow
• Particles are moving fast enough to
escape the attractive forces between
them
2 ways a liquid can become a gas:
• Evaporation
• boiling
Evaporation
• The vaporization of a liquid
that happens at the
SURFACE of the liquid.
Boiling point:
• The temperature at which a
liquid will enter the gaseous state
– happens throughout the
ENTIRE liquid
The movement of particles and the
collisions between them cause gases to diffuse.
Diffusion: • The spreading of particles throughout a given volume
until they are uniformly
distributed.
• Diffusion happens MOST
RAPIDLY in gases, but can
happen in liquids too.
PLASMA
PLASMA:
• Matter consisting of positively and
negatively charged particles.
• The overall charge of plasma is neutral
bc equal #’s of both charges are present.
Plasma
Characteristics of PLASMA • Most common state of matter in the
UNIVERSE.
• Very similar to the movement of gas
molecules, only faster.
Common examples of plasma:
Lightning
Bolts
Common examples of plasma:
Neon
signs
Common examples of plasma:
Fluorescent
tubes
Common examples of plasma:
stars
Common examples of plasma:
auroras
RECALL: • Particles move faster and
separate as the temperature
rises.
• When the temp of an object is
lowered, the particles slow down.
• The separation of the particles results in an expansion of the
entire object, known as
thermal expansion.
THERMAL EXPANSION:
• An increase in the size of a substance when the
temperature is increased.
The opposite is true too….
• Temp decreases, particles slow down
• Attraction bow particles increases,
pulling particles closer together
• Results in an overall shrinking of the substance, known as contraction.
Expansion joints in sidewalk
Strange behavior of water: • Water is an exception to the thermal
expansion rule:
– Temp increase, size increase
– Temp decrease, size decrease
• Water molecules have high negatively and
positively charged areas.
• As the temp of water decreases, particles
move closer together.
• The unlike charges will be attracted to each
other and line up so that only positive and
negative zones are near each other.
• This causes empty spaces to form in the
structure.
• These empty spaces are larger in ice than in
liquid water, so water expands when going
from a liquid to a solid state
• Solid ice is less dense than liquid
• Causes ice to float
PROPERTIES OF FLUIDS Section 2.4: (pg. 485-‐489)
Objectives
• Explain Archimedes’ principle
• Explain Pascal’s principle
• Explain Bernoulli’s principle and explain how
we use it.
Vocabulary:
Buoyancy pressure viscosity
Why do ships float?
Why do ships float? • They float because a greater force is
pushing up on the ship than the
force of the ship pushing down.
• This supporting force is called the buoyant force.
Buoyancy:
• The ability of a fluid-‐ a liquid or a gas-‐ to exert an upward
force on an object immersed
in it.
Archimedes' principle
Archimedes’ Principle • If the buoyant force is equal to the
object’s weight, the object will float.
• If the buoyant force is less than the object’s weight, the object will sink.
Remember:
• Density (D) = Mass (M)
Volume (V)
Density of water = 1 g/ml
Density • An object will float if its density is
less than the density of the fluid
it is placed in.
• The density of the steel block is greater than the density of water, so it sinks.
• The density of the wood block is less
than the density of water, so it floats.
Difference in mass
Wood block
• D = 5 gram /10 cm
• D = 0.5 g/cm
• Object floats
Steel block
• D = 20 gram / 10 cm
• D = 2 g/cm
• Object sinks
Difference in volume
Wood block
• D = 20 gram /30 cm
• D = 0.67 g/cm
• Object floats
Steel block
• D = 20 gram / 10 cm
• D = 2 g/cm
• Object sinks
Mass and Volume affect Density • If you formed that same steel block into the
shape of a hull filled with air, the same mass
would take up a larger volume.
• The overall density of the steel boat and air
would be less than the density of water
• The steel (boat) would now float
Mass and Volume affect Density
• The steel (boat) would now float.
Pascal’s Principle • Blaise Pascal (1692-‐1662), a French scientist discovered a useful property of
fluids.
Liquids AND Gases are considered to be
fluids because they both have the ability to
flow.
Pascal’s Principle
• According to Pascal’s Principle, pressure applied to a fluid is transmitted throughout
the entire fluid.
• http://www.youtube.com/watch?
v=epOwdGIDzlY
Example of Pascal’s principle • For example when you
squeeze one end of a
toothpaste tube,
toothpaste emerges from
the other end. The
pressure has been
transmitted through the
fluid toothpaste
Pressure:
• Force exerted per unit area.
• P= F / A
Applying the principle • Hydraulic machines are machines
that move heavy loads in accordance
with Pascal’s principle.
• (Ex: hydraulic lift in auto repair shops)
Hydraulic lift
1. A pipe filled
with fluid
connects small
and large
cylinders.
Applying the principle 2. Pressure applied
to the small
cylinder is
transferred
through the fluid
to the large
cylinder.
Bernoulli’s Principle
• According to Bernoulli’s principle,
as the velocity of a fluid
increases, the pressure exerted
by the fluid decreases.
Bernoulli’s Principle
Bernoulli’s Principle • The velocity of the air you blew over the
top surface of the
paper is greater than
that of the quiet air
below it.
Bernoulli’s Principle • As a result, the air pressure pushing
down on the top of
the paper is lower
than the air pressure
pushing up on the
paper.
Bernoulli’s Principle
• The net force below the paper
pushes the paper
upward.
Video Clips 16
Fun examples of Bernoulli’s Principle
• http://www.youtube.com/watch?v=P-‐
xNXrELCmU
Fluid Flow
• Another property exhibited by fluid is its tendency to flow.
• Fluids vary in viscosity: warm syrup
would flow faster when spilled than cold
syrup
• Viscosity: Resistance of liquid to flow.
Copyright © 2010 Ryan P. Murphy
High Viscosity = travels slow because of high resistance
High viscosity = flows slowly
Low viscosity= flows fast bc of low resistance
Low viscosity = flows quickly
• Activity! What is more viscous?
– Remember, Viscosity is resistance to flow.
Copyright © 2010 Ryan P. Murphy
Which is more viscous?
• Answer! The peanut butter doesn’t flow as
much as the ketchup so it has more viscosity.
Copyright © 2010 Ryan P. Murphy
Review Question:
• If the buoyant force on an object in a fluid is LESS than the object’s weight, the object will
________.
A. Float
B. Sink
Answer:
• If the buoyant force on an object in a fluid is LESS than the object’s weight, the object will
________.
A. Float
Review Question:
• According to Pascal’s principle, __________ applied to a fluid is transmitted throughout the
fluid.
A. Density B. Pressure C. Temp D. volume
Answer:
• According to Pascal’s principle, __________ applied to a fluid is transmitted throughout the
fluid.
A. Density B. Pressure C. Temp D. volume
Review Question
• The more viscous a fluid is the
______________ it will flow?
• Faster • Slower • Farther • Heavier
Answer:
The more viscous a fluid is the
______________ it will flow?
• Faster
• Farther • Heavier
BEHAVIOR OF GASES Section 2.5 (pg. 490-‐495)
Remember:
• Kinetic theory tells us that all gas particles are constantly moving and
colliding with anything in their path.
• The collision of these particles in the air result in pressure.
Pressure:
• Force exerted per unit area
• P = F / A
Gases are often confined to containers.
They remain
inflated bc of
collisions the air
particles have
with the walls of
the container
(balloon)
• The air molecules hitting the walls of
the balloon cause the walls to
expand outward.
• If more air is pumped into the
balloon, the # of air molecules is
increased.
This causes
more collisions
with the walls
of the
container
causing it to
expand.
Since the walls
of the bicycle
tube can’t
expand very
much, the
pressure within
the tube would
increase.
• Pressure is measured in a unit called Pascal
(Pa), the SI unit of pressure.
• Most pressures are expressed as kPa or 1,000
Pascals (sometimes called atm – atomic
pressure)
• The pressure of a gas depends on how often
its particles strike the walls of the container.
• If you squeeze gas into a smaller space, its
particles will strike the walls more often –
giving an increased pressure.
– The opposite is true too
• If you give the gas particles more space, they
will hit the walls less often – gas pressure is
reduced.
• British scientist named Robert Boyle
described this property of gases….
Boyle’s Law Pressure-‐Volume Relationship
• The pressure and volume of a sample of
gas at constant temperature are
inversely proportional to each other.
Boyle’s Law
• (as one goes up, the other goes down)
• P goes up, V goes up: P goes down, V goes
down
• P1V1 = P2V2
• If 3 of the variables are known, the fourth can
be calculated.
Work it out • The gas in a 20.0 mL container has a
pressure of 2.77 kPa. When the gas is
transferred to a 34.0 mL container at the
same temperature, what is the new pressure
of the gas?
• P 1V 1 = P2V2
Work it out • The gas in a 20.0 mL container has a
pressure of 2.77 kPa. When the gas is
transferred to a 34.0 mL container at the
same temperature, what is the new pressure
of the gas?
ANSWER: 1.63 kPa
• If a set amount of gas is transferred
into a larger container, would the
pressure go up or down?
• If a set amount of gas is transferred
into a larger container, would the
pressure go up or down?
Answer: DOWN
• Would there be more collisions, or
fewer collisions with the container
holding the gas if the gas was
transferred into a larger container?
• Would there be more collisions, or
fewer collisions with the container
holding the gas if the gas was
transferred into a larger container?
Answer: FEWER
Rationale: • The more volume (space) means fewer
collisions with the container, therefore
pressure goes down.
(from 2.77 kPa to 1.63 kPa)
Boyle’s Law in Action
• http://www.youtube.com/watch?
v=27yqJ9vJ5kQ
Charles’s Law
Temperature-‐Volume relationship
• At constant pressure, the volume of a
fixed amount of gas is directly
proportional to its absolute
temperature.
• As Temp goes up, V goes up
• As Temp goes down, V goes down
V1 V2
______ = _________
T1 T2
If 3 of the variables are known, the fourth can be calculated
Work it out: • What will be the volume of a gas
sample at 355K if its volume at 273K
is 8.5 L?
Work it out: • What will be the volume of a gas
sample at 355K if its volume at 273K
is 8.5 L?
ANSWER: 11.1 L
• If the temperature of a given
quantity of gas is increased, what
will happen to the volume it
occupies? (In an elastic container?)
• If the temperature of a given quantity of gas is
increased, what will happen to the volume it
occupies? (In an elastic container?)
ANSWER: volume would increase (container
would get bigger)
Rationale:
• Gas particles moving faster would
have more collisions with the
container and exert more force to
enlarge the volume of the elastic
container.
Fun with Charles’s Law
• http://www.youtube.com/watch?v=Jeso
• E4F2Pb20
• http://www.youtube.com/watch?
v=GcCmalmLTiU
Review Question • Boyle’s Law states that as the pressure
exerted on a container of gas increases, the
volume of the gas will _____.
A. Increase B. decrease
C. Stay the same D. none of the above
ANSWER: • Boyle’s Law states that as the pressure
exerted on a container of gas increases, the
volume of the gas will _____.
A. Increase B.
C. Stay the same D. none of the above
REVIEW QUESTION: