Heat Transfer & Change of Phase

Heat’s Movement & Effect

Conduction-Particle Collision• Heat conduction occurs by electrons colliding• Loosely held electrons are good conductors of

heat. Examples: Metals-Ag, Cu, Al, Fe• Tightly held electrons are good insulators of

heat. Examples: wool, wood, paper, cork, plastic foam

• What are ways you are affected by this?

Copper- Notice the N-Shell loosely held electron

Molecular structure of cork is very stable. All electrons are held tightly in complete electron shell orbitals.

Molecules are generally more stable because they are pairing with other atoms sharing or exchanging electrons.

Name some common insulators ? Good insulator=Poor Conductor

Good Conductor =Poor Insulator!

Convection-Heat Transfer by Movements of Fluid

• Heat is transferred by currents of the fluid• Examples: Water, Warm Air• Applications: Convection ovens, Warm winds

Papers blow on top of radiator; convection currents

Convection oven fan

Radiation- Heat Transfer by Radiant Energy

The wavelength of radiation relates to frequency. A high temperature source emits high frequency wavelengths.

Radiant Energy

• Emission-• Average frequency is

directly proportional to temperature

• Sun transmits radiation• Earth transmit radiation

• Absorption-• Everything is emitting and

absorbing radiation continuously

• Dark objects absorb radiant energy better

• Dark objects emit radiant energy better

• Light colored objects reflect radiant energy better

Matter in 4 Phases

• Solid- Ex. Ice• Liquid- Ex. Water• Gas- Ex. Steam• Plasma- Ex. Illuminating gas (found in

fluorescent bulb, sun, stars)

Phase Diagram for Water

P=PressureFrom the atmosphere

T=TemperatureMeasured inCelsius degrees

Triple Point =All 3 states exist

Critical Point=Plasma properties begin

Energy Required forEach Change of Phase

• Heat of Vaporization- Amount of heat required to vaporize one gram of a liquid at its boiling point with no change in temperature. J/g

Condensing <- -> Evaporating• Heat of fusion- Amount of heat required to melt one gram of a solid at

its melting point with no change in temperature J/g

Melting <- -> Freezing• Sublimation- The direct vaporization of a solid by heating without

passing through the liquid state

• Sublimation <- -> Deposition

What Changes of Matter do you See?What Energy is required for change?

Sublimation of Dry Ice

Heat of Fusion- Freezing ice cubes

Heat of vaporization- Water Evaporating in clouds

Heat of fusion- melting popsicle

Heat of vaporization- Water condensing into rain from clouds

Phase Changes with Temperature Changes on Water-Note the red lines-Melting/Vaporization

Known as “Heating curve of Water”You can flip temperature and have A-B start as a vapor

Boyles Law

Charles Law

The volume of a gas varies inversely with the pressure applied to it as long as the temperature and amount of gas remain constant.

P1V1 = P2 V2 whereas (Pressure 1) (Volume 1) = (Pressure 2) (Volume 2)

You can solve for one unknown with the following equation.P1 = P2 V2 As Volume decreases, Pressure increases. V1 As Pressure increases, Volume decreases.

The volume of a gas varies directly with its temperature as long as the pressure and the amount of gas remain constant.

V1 = V2 whereas (Volume 1) = (Volume 2)T1 T2 (Temperature 1) (Temperature 2)

You can solve for one unknown with the following equation.V1 = V2 T1 As Temperature increases, Volume increases T2 As Temperature decreases, Volume decreases