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Chapter 16
Kinetic Theory
 Definition - an explanation of how particles
in matter behave
Kinetic Theory Assumptions
 All matter is composed of small particles
 These particles are in constant motion
 These particles are colliding with each
other and the walls of their container
Thermal Energy
 Thermal energy is the TOTAL ENERGY of
a material’s particles
 Kinetic Energy - vibrations and movement
within and between particles
 Potential Energy - result from forces that act
within or between particles
Temperature
 Definition - average KINETIC ENERGY in
the substance (have fast the particles are
moving)
 Water at 0 oC will have LOWER AVERAGE
KINETIC ENERGY than water at 100 oC.
 Molecules will have some movement and
kinetic energies at all temperatures, except at
ABSOLUTE ZERO
States of Matter - Solids
 Particles are CLOSELY PACKED together
 Have a definite SHAPE and VOLUME
 Kinetic energy is LOW
States of Matter - Liquids
 Particles PARTIALLY OVERCOME
attractive forces
 Take shape of CONTAINER but have
definite VOLUME
 Kinetic energy is MODERATE
Vital Terminology
 MELTING POINT is the temperature at
which a solid begins to liquefy
 HEAT OF FUSION is the amount of
energy required to change a substance
from a solid to a liquid phase
States of Matter - Gas
 Particles COMPLETELY OVERCOME
attractive forces and are FAR APART
 No DEFINITE SHAPE or volume
 Kinetic energy is HIGH
Vital Terminology Part 2
 VAPORIZATION occurs when particles are
moving fast enough to completely escape the
attractive forces of other particles
 BOILING POINT is the temperature at which the
PRESSURE of the vapor in the liquid is equal to
the external pressure acting on the SURFACE of
it
 HEAT OF VAPORIZATION is the amount of
energy required for a liquid at its boiling point to
become a gas
States of Matter - Plasma
 Matter consisting of POSITIVELY and
NEGATIVELY charged particles
 The forces produced from HIGH-ENERGY
COLLISIONS are so great that electrons
from the atom are stripped off.
 Plasma is found in all observed STARS
and in LIGHTNING BOLTS.
Thermal Expansion
 Definition - an increase in the size of a
substance when the temperature is
increased
 In Liquids  THERMOMETERS
 In Gases  HOT AIR BALLOONS
 Water is unique because IT DOESN’T
FOLLOW THIS PATTERN
Buoyancy
 Definition - the ability of a fluid (a liquid or
gas) TO EXERT AN UPWARD FORCE on
an object immersed in it
 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
Archimedes' Principle
 The BUOYANT FORCE on an object is
equal to the WEIGHT OF THE FLUID
displaced by the object
Pascal’s Principle
 Pressure applied to a fluid is transmitted
throughout the fluid
Pressure
 force exerted PER UNIT AREA
 Formula:
p = F/A
 Application  Hydraulics
Example Problem
A heavy crate applied a force of 1,500
N on a 25-m2 piston. What force
need to be exerted on the 0.80-m2
piston to lift the crate?
Bernoulli’s Principle
 As the velocity of a FLUID INCREASES,
the PRESSURE EXERTED by the fluid
DECREASES
Viscosity
 Definition - the resistance of a fluid to
flow