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 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. Good Conductor = Poor Insulator! Good insulator=Poor Conductor Name some common insulators ?

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=Pressure From the atmosphere T=Temperature Measured in Celsius degrees Triple Point = All 3 states exist Critical Point= Plasma properties begin

Energy Required for Each 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? Heat of vaporization- Water Evaporating in clouds Heat of Fusion- Freezing ice cubes Sublimation of Dry Ice 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 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. Charles Law 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