Thermal Energy
• Temperature
– THE AVERAGE KINETIC ENERGY OF AN OBJECT.
• Average motion energy
• Thermal Energy
– THE TOTAL KINETIC + POTENTIAL ENERGY IN AN
OBJECT.
• Energy of stored bonds + motion
• Temperature Reference Points
• Freezing Point of Water
– 0 °C
or
32°F
• Boiling Point of Water
– 100°C
or
212°F
Temperature Conversions
TK = Temperature in Kelvin
TC = Temperature in °C
TF = Temperature in °F
Temperature (°F)
212
32
0
100
Temperature (°C)
Temperature Conversions
℃→℉
9
℉ = ( )(℃) + 32
5
℉→℃
5
℃=
9
℃→K
℉ − 32
K = ℃ + 273
HEAT
TRANSFER
1.
Which object has the greatest temperature?
2.
Which object has the greatest average kinetic energy?
3.
Which object has the greatest total kinetic energy?
4.
Which object has the greatest Thermal Energy?
5.
Which object, left on its own, in outer space, has the greatest heat?
6.
Which object, connected to the table, has the greatest heat transfer?
A.
97°C
50 mL
B.
7°C
1L
C.
-2°C
1000 kL
D.
None of these
Heat
• HEAT = THERMAL ENERGY THAT IS TRANSFERRED
FROM ONE OBJECT TO ANOTHER.
• HEAT ALWAYS FLOWS FROM THE HIGHER
TEMPERATURE TO THE LOWER TEMPERATURE
• Touch the leg of your chair and the leg of your
desk. Which one is colder?
Pizza Capacity
• Think and Explain?
When I throw my pizza into the microwave to
warm it up, it isn’t the same temperature
throughout. Why?
Heat Capacity
• All substances will change temperature as
they gain thermal energy.
• HEAT CAPACITY = THE AMOUNT OF
TEMPERATURE CHANGE TO A HEATED OBJECT
DEPENDS ON THE OBJECT AND THE MASS.
• The three methods of Heat Transfer
– CONDUCTION
– CONVECTION
– RADIATION
Modes of Heat Transfer
Conduction
• CONDUCTION = THERMAL ENERGY TRANSFERRED BY
THE COLLOSIONS OF PARTICLES
• CONDUCTION REQUIRES CONTACT
– It is an exchange of energy between atoms and electrons by
collisions
– Less energetic particles gain energy during collisions with more
energetic particles.
Materials
Listed are common
materials. Better
conductors have a
higher thermal
conductivity
Demo POOR CONDUCTOR = GOOD
INSULATOR
Conduction Examples
• Why is the tile cold
and the carpet feel
warm?
• Because the tile is a
better conductor and
it has a greater heat
capacity
Convection
• What is convection?
• THERMAL ENERGY TRANSFERRED BY A CURRENT
OF FLUID
• REQUIRES A FLUID(Gas/Liquid)
– When the movement results from differences in
density, it is called natural convection
– When the movement is forced by a fan or a pump, it
is called forced convection
Convection Heating
• An example of
natural
convection
• Explain what is
happening
• Water Temp
Demo
Convection Current Example
• What is the forced
convection?
• What is the natural
convection?
Weather – due to natural convection
Radiation
• RADIATION = THERMAL ENERGY
TRANSFERRED BY ELECTROMAGNETIC WAVES
• RADIATION DOES NOT REQUIRE CONTACT
• All objects radiate (give off) energy
continuously in the form of electromagnetic
waves due to thermal vibrations of the
molecules
Thermal Expansion
• When an object is heated, it’s particles speed
up and spread apart, making the object
expand.
• Demo • Uses: Cavities, Bridges, Sidewalks Lines
• Downsides - potholes
Radiation example
• No physical contact is necessary
• The electromagnetic waves carry
the energy
• The heat transfer cannot be accounted for by
conduction or convection (thru space)
States of Matter
Picture Volume
Gas
Liquid
Solid
Shape
Kinetic
Energy
Intermolecular
Force
Picture
Phase
Summary
Definite
Definite
Kinetic
Volume
Shape
Energy
Intermolecular
Force
High
Gas
No
No
Sometimes
bounce off
one another
None
Medium
Liquid
Yes
No
Roll, Bounce
off one
another
Weak
Low
Solid
Yes
Yes
Shake back
and Forth
Strong
States of Matter Notes
• These are found online at
• http://prezi.com/_2quyv8zpnzq/notes-statesof-matter/
• (Look at these or you’ll be sorry).
Crystalline
Amorphous
Definite Shape
Least Kinetic energy
Definite Volume
Medium Kinetic
energy
Property of
Viscosity
Molecules
in motion
No Definite
Shape
Fluid
Condensation
Vaporziation
Highest Kinetic Energy
Phase Change
Graphs
Thermal Energy and Phase Changes
150
Vaporization
Temperature (°C)
100
Condensation
50
Melting
0
Freezing
0
1
2
3
Thermal Energy
4
5
Phase Change Process (S & L)
• Melting – THERMAL ENERGY IS USED TO BREAK BONDS
– The bonds that hold molecules in vibrating lattice
structure are breaking.
– The Intermolecular Forces Lessen
• Freezing – THERMAL ENERGY IS USED TO CREATE
BONDS AND HOLD MOLECULES IN PLACE
– The bonds that will hold molecules in position are forming
– The Intermolecular Forces Increase
–Melting Point – THE TEMPERATURE AT WHICH AN
OBJECT EITHER MELTS OR FREEZES.
Evaporation = Escape
• Brant’s Maximum Security Penitentiary for
Incarcerated Dress Code Violators and Others.
• If the highest IQ’s escape, what happens to
the average Penitentiary IQ.
– Up
– Down
– Same
VAPORIZATION (L – G)
• EVAPORATION – A CHANGE IN PHASE FROM
LIQUID TO GAS AT THE SURFACE.
– This cools the remaining liquid!
• BOILING – A CHANGE IN PHASE FROME
LIQUID TO GAS BELOW THE SURFACE.
– This cools the remaining liquid!
• Boiling Point – THE TEMPERATURE THAT AN
OBJECT VAPORIZES OR CONDENSES.
Condensation (G  L)
• CONDENSATION – A CHANGE OF PHASE FROM GAS TO
LIQUID.
• This is a WARMING PROCESS for the liquid.
• Gas molecules strike surface of liquid and give up so
much energy that they can’t stay in gaseous phase
• Examples
Droplets forming on mirror
Droplets on glass of water
Condensation = Captured
• The smart kids sneak out of a convocation in
the gym and join the prison of ISS. What
happens to the average IQ of the prison?
– Up
– Down
– Same
Phase Changes with the Gizmo
• The differences with this type of graph, and
the basic phase change graph is that the time
is the x-axis instead of changing thermal
energy.
• Hint: In these graphs Mr. Nuetzel had an initial
setup, then didn’t change any of the settings
after starting it.
Phase Change Gizmo
With this setup, what will happen to the temp. graph?
Phase Change Gizmo
With this setup, what will happen to the temp. graph?
Phase Change Gizmo
With this setup, what will happen to the temp. graph?
Phase Change Gizmo
With this setup, what will happen to the temp. graph?
What’s the difference between these two
graphs?
What’s the difference between these two
graphs?
Phase Change Gizmo
With this setup, what will happen to the temp. graph?
Interpreting Graphs
• Hint – Mr. Nuetzel didn’t keep the RATE of
heat transfer constant in these graphs.
What is happening in this graph?
What is happening in this graph?
What is the difference in these graphs?
What is happening in this graph?
What is happening in this graph?
What is happening in this graph?
Acting Out Phase Changes
• Get in a group of 8-12 students. You will have
2 minutes to decide how you want to act out
one of the phase changes that H2O can go
through with either an addition or subtraction
of thermal energy.
• Demonstrate your skit to the class.
Review Discussion Questions
• Explain in detail and use the thermal energy
vocabulary.
• When I throw my pizza into the microwave to
warm it up, it isn’t the same temperature
throughout. Why?
• How is the house heated?
• How does a thermometer work?