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

0 100 Temperature (°C)

212

32

Tem

pera

ture

(°F)

Temperature ConversionsTK = Temperature in KelvinTC = Temperature in °CTF = Temperature in °F

Temperature Conversions

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°C50 mL

B. 7°C1 L

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.

Modes of Heat Transfer

• The three methods of Heat Transfer

– CONDUCTION

– CONVECTION

– RADIATION

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.

MaterialsListed 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 Shape Kinetic Energy

Inter-molecular

Force

Gas

Liquid

Solid

Phase SummaryPicture Definite

VolumeDefinite Shape

Kinetic Energy

Inter-molecular

Force

Gas No NoHigh

Sometimes bounce off

one another

None

Liquid Yes NoMedium

Roll, Bounce off one another

Weak

Solid Yes YesLow

Shake back and Forth

Strong

States of Matter Notes

• These are found online at • http://prezi.com/_2quyv8zpnzq/notes-states-

of-matter/

• (Look at these or you’ll be sorry).

Deposition = Frost

Condensation

Amorphous

Definite Shape

No Definite Shape

Fluid

Molecules in motion

Vaporziation

Melti

ng

CrystallineFre

ezing

Definite Volume

No Definite Volume

Least Kinetic energy

Medium Kinetic energy

Property of Viscosity Highest Kinetic Energy

Sublimation = Dry Ice

Phase Change Graphs

0 1 2 3 4 5 Thermal Energy

150

100

50

0

Tem

pera

ture

(°C)

Thermal Energy and Phase Changes

Freezing

Liqui

d

Gas

Condensation

Melting

Solid

Vaporization

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

• ExamplesDroplets forming on mirrorDroplets 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 GizmoWith this setup, what will happen to the temp. graph?

Phase Change GizmoWith this setup, what will happen to the temp. graph?

Phase Change GizmoWith this setup, what will happen to the temp. graph?

Phase Change GizmoWith 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 GizmoWith 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?