Expansion and Contraction Power P. Notes

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EXPANSION AND
CONTRACTION
KEY POINTS TO REMEMBER….
 As the temperature of a solid, liquid or g as increases,the average
distance between the atoms/molecules of the substance typically
increases, causing the substance to expand.
 As the temperature of a solid, liquid or g as decreases, the average
distance between the atoms/molecules typically decreases, causing the
substance to contract.
 Heat expansion or contraction can happen to solids, liquids, and gases.
 Expansion or contraction due to changes in temperature is not permanent
(e.g., objects that expand when heated can also contract when cooled).
 The number of atoms and the mass of the atoms DOES NOT CHANGE with
changes in temperature. ONLY T HE SPACING BET WEEN PARTICLES
CHANGES.
 Dif ferent types of solids, liquids or gases expand and contract dif ferently.
For example solid metals that are made of pure elements like copper and
aluminum are better at absorbing heat than alloy metals like brass. Gold
is probably the best heat conductor, but it is so expensive that we don’t
use it much.
 Brass is an alloy of copper and zinc. An alloy is a metal made from combining two
or more metallic elements.
EXPANSION AND CONTRACTION OF
MATTER IN GENERAL
Contraction
 As the average energy
(temperature) of particles
decrease, the space
between the particles
decrease. Matter in the
solid liquid and gas phase
CONTRACTS!
Expansion
 As the average energy
(temperature) of particles
increase, the space
between the particles
increase. Matter in the solid
liquid and gas phase
EXPANDS!
EXPANSION AND CONTRACTION
IN SOLIDS
Solids
can EXPAND or CONTRACT depending on the
temperature (average energy of the particles).
 For Example
 Metal Loop and Ball Demonstration
 Does the ball fit in the loop when the loop and ball are cool?
 Will the ball fit in the loop when the loop is heated? Why or Why Not?
EXPANSION AND CONTRACTION
IN LIQUIDS
 Liquids can EXPAND or CONTRACT depending on the
temperature (average energy of the particles).
 This is demonstrated by the liquid used in a thermometer. As
the liquid expands and contracts, it moves up and down the
inside tubing ( the bore ) of the thermometer. Numbers are
placed alongside the glass tube that mark the temperature
when the line is at that point.




This liquid is sometimes colored alcohol but can
also be a metallic liquid called mercury.
Both mercury and alcohol grow bigger
when heated and smaller when cooled.
GALILEO THERMOMETER
 A Galileo thermometer (or Galilean thermometer) is
a thermometer made of a sealed glass cylinder containing a
clearliquid and several glass vessels of varying densities. As
temperature changes, the individual floats rise or fall in
proportion to their respective density.
 The clear liquid in which the bulbs are submerged is not
water, but some organic compound (such as ethanol) the
density of which varies with temperature more than does
water’s. This change of density of the outer clear liquid, with
temperature change, causes the bulbs to rise or sink.
GALILEO BAROMETER
 When a low -pressure weather system approaches, the weight
of the air pressing on the open end of the spout decreases,
allowing the water level to rise. Conversely, when a high pressure system moves in, it will push the water level down. A
scale can be printed on the spout corresponding to the inches
of mercury, normally between 28 and 32 inches.
EXPANSION AND CONTRACTION
IN GASES
 Gasses can EXPAND or CONTRACT depending on the
temperature (average energy of the particles).
 What does Charles Gas Law say?
(see book page 36)
 Under extremely high temperature conditions (like
the temperatures inside the Sun, particles can be
split into what makes them up (electrons and quarks
etc). This creates a fourth state of matter called
plasma.
DOES VOLUME OR MASS CHANGE
WHEN SOMETHING IS HEATED OR
COOLED?
Volume
Before Heating Volume cm
After Heating
Volume cm
Mass
Balloon Only
Balloon Tape
Balloon, Tape and
Air
Air Only
2.16 g
.01 g
2.31 g
.14 g
2.16 g
.01 g
2.31 g
.14 g
WHAT DO THE PARTICLES OF MATTER DO
WHEN HEATED?
 Particles
 Particles
EXAMPLES OF EXPANSION/CONTRACTION
IN A SOLID, LIQUID AND GAS
 http://www.project2061.org/publications/EducatorsGuide/onl
ine/Examples/Expansion/expansion.html
STEEL BRIDGES
 Have expansion joints.
BRIDGE EXPANSION JOINT
EXAMPLE
RAILROAD TRACKS
 Have gaps at each joint.
RAILROAD RAILS
CONCRETE ROADS
 Have expansion joints built in.
CONCRETE ROADS
CONCRETE ROADS
SIDEWALKS
 Sidewalks are built with expansion joints to try and avoid the
cracking that may occur.
 Sometimes a sidewalk will develop a crack even with
expansion joints. Do you know what happens to the size of the
cracks in the winter and summer?
SIDEWALKS
CARS
 Cars have engines with many working parts. The parts are
engineered to be a little loose when cold so that when the
engine becomes warm the parts do not expand to be to tight.
STUDY THE CHART AND SUMMARIZE IN
YOUR OWN WORDS IT’S MEANING.
 Quick Review
ENGINEERING DISASTERS
 Tacoma Narrows Bridge
QUIZ!
 Summary Sentences.
 1. When matter is heated the particle’s speed _________ and the
spacing_________.
 2. When matter is cooled the particle’s speed _________ and the
spacing _________.
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