Chapter 9 HEAT Chapter 9 HEAT

Goals: Temperature vs Heat, Goals: Temperature vs Heat,

Thermal Energy, Temperature Thermal Energy, Temperature conversions, Specific Heat conversions, Specific Heat

Capacity, Phase changes and Capacity, Phase changes and Latent HeatLatent Heat

TemperatureTemperature Measure of average kinetic energy of Measure of average kinetic energy of

particlesparticles atoms and moleculesatoms and molecules Internal energy – energy of atomic motion Internal energy – energy of atomic motion

that causes temperatures to rise Uthat causes temperatures to rise U Motion of particles can be:Motion of particles can be: Translational – linear monatomic gasTranslational – linear monatomic gas Rotational – spinning molecularRotational – spinning molecular Vibrational – back + forth molecularVibrational – back + forth molecular

Thermal ExpansionThermal Expansion

Occurs as a result of an increase of Occurs as a result of an increase of internal energy and motion of particles internal energy and motion of particles

Kinetic EnergyKinetic Energy ex: side walk expansion groves and ex: side walk expansion groves and

thermometersthermometers Dependent upon the type of materialDependent upon the type of material Thermal equilibrium – temperature Thermal equilibrium – temperature

indicates conditions are not changingindicates conditions are not changing

Temperature ConversionsTemperature Conversions Scales include: Fahrenheit, Celsius Scales include: Fahrenheit, Celsius

and Kelvinand Kelvin F 32-212 C 0-100 K ab F 32-212 C 0-100 K ab

zero- ?zero- ? TT°F°F = (9/5 T = (9/5 T°C) + 32°C) + 32 T°C = 5/9 (T°F – 32)T°C = 5/9 (T°F – 32) K = °C + 273.15K = °C + 273.15 °C = K – 273.15°C = K – 273.15 -40°F = -40°C-40°F = -40°C Practice Problems A pg 303 Practice Problems A pg 303

HeatHeat

Thermal Energy that is transferred Thermal Energy that is transferred Cause of particle vibration or KE increaseCause of particle vibration or KE increase High to Low (heat movers)High to Low (heat movers) Depends upon:Depends upon: temperature mass specific heat capacity temperature mass specific heat capacity Units are Joules cal kcal Btu ThermsUnits are Joules cal kcal Btu Therms 4.186 J = 1 cal 4186 J = 1 kcal 4.186 J = 1 cal 4186 J = 1 kcal

Btu = 1055 J Btu = 1055 J Therm = 100,000 BtuTherm = 100,000 Btu

The greater the temperature difference the The greater the temperature difference the faster the rate of heat transfer faster the rate of heat transfer

Heat TransferHeat Transfer

Conduction, Convection and RadiationConduction, Convection and Radiation Conduction – heat transfer from particle to Conduction – heat transfer from particle to

particle in contact most important in particle in contact most important in solids influenced by specific heat solids influenced by specific heat capacitycapacity

Convection – rising and sinking currents Convection – rising and sinking currents important in fluidsimportant in fluids

Radiation – electromagnetic waves in Radiation – electromagnetic waves in matter and through empty spacematter and through empty space

Heat Transfer can cause a Heat Transfer can cause a Phase changePhase change

Phase change diagram displays Energy vs Phase change diagram displays Energy vs Temperature Temperature

Solid – FP – heat of fusion – MP – Liquid - Solid – FP – heat of fusion – MP – Liquid - CP – heat of vaporization – BP – Gas as CP – heat of vaporization – BP – Gas as a substance is heateda substance is heated

condensation = warming process condensation = warming process evaporation = cooling processevaporation = cooling process

Q = m Q = m ΔΔT Cp H2O = 4189 J/kg°CT Cp H2O = 4189 J/kg°C Calorimetry Lab Calorimetry Lab Problems on handoutProblems on handout

Latent HeatLatent Heat

Hidden Heat Hidden Heat water has a high heat capacity and water has a high heat capacity and

can store much heat energycan store much heat energy heats of fusion and vaporization heats of fusion and vaporization

required to rearrange atoms and required to rearrange atoms and disrupt intermolecular forcesdisrupt intermolecular forces

Just Think……………..Just Think…………….. The extreme cold is not just an Arctic The extreme cold is not just an Arctic

BlastBlast or a reason to be out of school for a or a reason to be out of school for a

weekweek it is the absence of thermal energyit is the absence of thermal energy or HEATor HEAT so…………………………so………………………… be Cool be Cool and don’t forget to read pages 298-and don’t forget to read pages 298-

308 and 313-317308 and 313-317