Thermal Energy Transfer and absorption. Thermodynamics Thermodynamics-study of heat transformations into other forms of energy.

Thermal EnergyTransfer and absorption

Thermodynamics

Thermodynamics-study of heat transformations into other forms of energy

Heat

Fire dissipates heatDoes not absorb heat

Heat always flows from a hotter to cooler

Heat flowing from hotter to cooler

Grease fire

http://www.gocolumbiamo.com/Fire/Educational/stovefires.phphttp://www.teachertube.com/view_video.php?viewkey=d76c5ec1acefe6d433b6http://www.teachertube.com/view_video.php?viewkey=e0da400d9b98c254b9fc

Thermal Energy

Thermal Energy- total energy of the molecules

Temperature- related to average energy per molecule

Thermal Energy and Temperature

Temperature-quantifies the average kinetic energy of the particles in an objectThe warmer an object the more kinetic

energy it has.KEavg=KEt/(number of particles)

Thermal Energy- proportional to the number of particles

Equilibrium and Thermometry

Hot = particles move faster = more thermal energy

Conduction-transfer of kinetic energy when particles collideenergy transferred from a warmer object to a colder object

How much energy is in an object at 0 Kelvin (absolute zero)?

“Scientists put a light wave on hold”

http://www.msnbc.msn.com/id/3077366/

Equilibrium and Thermometry

Thermal Equilibrium- the state in which the rate of energy flow between two objects is equal and the objects are at the same temperatureSame temperature

Temperature Scales

Celsius- The zero point is the freezing point of

waterThe 100 point is the boiling point of

water

KelvinThe zero point is where all thermal

energy has been removed. No lower possible temperature, No motion in the atoms. Absolute Zero

0 K =- 273.15 CTc + 273 = TK

Temperature Scales

FahrenheitThe zero point is determined by a

frigorific mixture of ice, water, and ammonium chloride (a salt). The mixture automatically stabilizes its temperature at 0 °F

The second point is the 32 degree found by putting the thermometer in still water as ice is just forming on the surface.

The third point, the 96 degree, was the level of the liquid in the thermometer when held in the mouth or under the armpit. (Has been since adjusted to 98.6)

Three Temperature Scales

Three Temperature Scales

HeatAnd how it transferred

Heat

Heat-energy that always flows from the hotter object to the cooler object. “Left to itself heat never flows from a colder

object to a hotter object.”

Variable ‘Q’ denotes heatQ is in joules or J

Flow of Thermal Energy

Conduction

Convection

Radiation

Conduction

Heat is transferred (conducted) through particles that are in direct contact with each other.

Convection

The motion of fluid in a liquid or gas caused by temperature differences

Hotter fluids/gases rise.Cooler fluids/gases sink.

“Real power from nothing but hot air”http://www.guardian.co.uk/environment/2002/aug/19/energy.renewableenergy

Radiation

The transfer of energy by electromagnetic waves

Does not require contactTravels at 3x10^8 m/s

Nuclear Test Site, Ground Zero

Specific Heat

The amount of energy that must be added to a material to raise the temperature of a unit mass by one temperature unit.

Heat Transfer

Q = mC∆T = mC(Tf –Ti)

Q = heatm = massC = specific heatT = temperature

Temperature intervals for Kelvin and Celsius are the same, (i.e. ∆T is the same)

Ex 1, pg318 3-5 , pg 319

Conservation of Energy

The total energy in an isolated, closed system never changes.

EA + EB = constant

1)

2) 0

3)

A A A B B B

A A A B B Bf

A A B B

E q mC T

m C T m C T

m C T m C TT

m C m C

Ex 2, pg321 6-7, pg321

Homework

Pg 322 # 10, 12, 16, 17

Pg 336#37, 39, 50, 52, 53, 57

Changes of State and the Laws of Thermodynamics

Change in state changes structure and the way in which atoms store thermal energy

States of matter

SolidLiquidGasPlasma

Change-of-State

Changes of State

Melting Point Heat of FusionQ=mHf

Boiling PointHeat of VaporizationQ=mHv

Condensation PointFreezing Point

Heat = Q in Joules J

Thermal energy

Increase thermal energy Increases particle speedCauses more freedom of movement

Change-of-State

All thermal energy added goes to overcome the forces holding the particles together. The temperature does not increase

Melting

Boiling

The First Law of Thermal Dynamics

Change in thermal energy is equal to the heat added minus the work done

∆U=Q-WWhere

∆U is the change in thermal energyQ is the heat addedW is the work done

Efficiency

W/QH

How your refrigerator works

The Second Law of Thermal Dynamics

Natural processes go in a direction that maintains of increases the total entropy of the universe.

Things get more disordered over time, assuming time is going forward.

The Animate and the Inanimate(available on class website)

Read Pg 4-8,42 Explain what it means

One page write-up

Entropy

Entropy – the measure of disorder in a system

Change in Entropy – is equal to the heat added divided by the temperature in kelvins

∆S=Q/T

The measure of unavailability of useful energy

Temperature and Thermal Energy

Describe thermal energy and compare it to potential and kinetic energies.

Distinguish between temperature and thermal energy

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