Thermal Energy Thermal Energy and Heatand Heat

Kinetic Theory of Kinetic Theory of MatterMatter

ALL particles that make up ALL particles that make up matter are constantly in matter are constantly in motion.motion.

ALL particles in matter have ALL particles in matter have kinetic energy.kinetic energy.

Within a substance, not all Within a substance, not all particles move at the same particles move at the same rate.rate.

TemperatureTemperatureA measure of the A measure of the

averageaverage kinetic energy kinetic energy of the individual of the individual particles of matterparticles of matter

Depends on mass as Depends on mass as well as speedwell as speed

TemperatureTemperatureThermometerThermometer is used to is used to

measure temperaturemeasure temperature3 common scales3 common scales

FahrenheitFahrenheitCelsiusCelsiusKelvinKelvin

Fahrenheit ScaleFahrenheit Scale Most common in the U.S.Most common in the U.S. 3232oo = water freezes = water freezes 212212oo = water boils = water boils Intervals in between are Intervals in between are

divided into divided into 180 equal 180 equal intervals called degrees intervals called degrees Fahrenheit (Fahrenheit (ooF)F)

Absolute zero = -459 degreesAbsolute zero = -459 degrees

Celsius ScaleCelsius Scale Used in most of the worldUsed in most of the world 00oo = water freezes = water freezes 100100oo = water boils = water boils Intervals divided into Intervals divided into 100 100

equal parts equal parts called called degrees Celsius (degrees Celsius (ooC)C)

Absolute zero = -273 Absolute zero = -273 degreesdegrees

Kelvin ScaleKelvin Scale Most commonly used in Most commonly used in

physical sciencephysical science 273 degrees = water 273 degrees = water

freezesfreezes 373 degrees = water boils373 degrees = water boils Kelvin scale is designed so Kelvin scale is designed so

that 0 = absolute zerothat 0 = absolute zero

Conversion between Celsius Conversion between Celsius and Fahrenheitand Fahrenheit

Thermal EnergyThermal EnergyThe total energy of all The total energy of all

of the particles in a of the particles in a substance or materialsubstance or material

The The more particlesmore particles a a substance has at a substance has at a given temperature; the given temperature; the more thermal energymore thermal energy it it hashas

Thermal EnergyThermal EnergyExample: 2L of hot Example: 2L of hot chocolate at 75chocolate at 75oo has has more thermal more thermal energy than 1.5L of energy than 1.5L of hot chocolate at 75hot chocolate at 75oo

Thermal EnergyThermal EnergyThermal energy depends Thermal energy depends

on:on: temperature temperature # particles in a substance# particles in a substance how the particles are how the particles are arrangedarranged

HeatHeatMovement of thermal Movement of thermal

energy from a energy from a substance at a substance at a higherhigher temperature to temperature to another at a another at a lowerlower temperaturetemperature

HeatHeatWhen energy flows When energy flows

from one object to from one object to another; the thermal another; the thermal energy of BOTH energy of BOTH objects changesobjects changes

Ex: ice cube in bowlEx: ice cube in bowl

Measuring HeatMeasuring Heat CalorieCalorie

Amount of energy needed Amount of energy needed to raise the temp. of 1g of to raise the temp. of 1g of water by 1 degree Celsiuswater by 1 degree Celsius

JouleJouleSI unit for energySI unit for energyOne calorie = 4.18JOne calorie = 4.18J

Measuring HeatMeasuring Heat 1 C = 1kilocalorie (1000 1 C = 1kilocalorie (1000

calories)calories)Each calorie of food Each calorie of food

contains 1000 calories contains 1000 calories of energyof energy

Measured by a Measured by a calorimetercalorimeter

Specific HeatSpecific Heat A quantity to measure the A quantity to measure the

relationship between heat relationship between heat and temperature changeand temperature change

Amount of energy required Amount of energy required to raise the temperature of to raise the temperature of 1g of a substance by 11g of a substance by 1ooCC

Every substance has its own Every substance has its own specific heatspecific heat

Heat TransferHeat Transfer3 ways heat can be 3 ways heat can be

transferred:transferred:ConductionConductionConvectionConvectionRadiation Radiation

ConductionConduction Heat is Heat is

transferred transferred without the without the movement movement of matter of matter itselfitself

Heat is Heat is transferred transferred by touchingby touching

ConvectionConvection

Transfer of heat by Transfer of heat by the movements of the movements of a fluida fluidGas or liquidGas or liquid

Convection CurrentConvection Current

Movement of a fluid Movement of a fluid caused by differences caused by differences in temperaturein temperature

RadiationRadiationTransfer of energy by Transfer of energy by

electromagnetic waveselectromagnetic wavesFeel radiation from a Feel radiation from a

bonfire; heat lampbonfire; heat lampDOES NOT require DOES NOT require

matter to transfer matter to transfer thermal energythermal energy

Heat TransferHeat Transfer Heat flows into a Heat flows into a

substance; thermal energy substance; thermal energy increases; as thermal increases; as thermal energy increases, energy increases, temperature increasestemperature increases

Heat will flow until 2 Heat will flow until 2 substances have same substances have same temperaturetemperature

Heat TransferHeat TransferExample: ice Example: ice creamcreamHeat from Heat from ingredients flows ingredients flows to the iceto the ice

ConductorsConductorsA material that A material that

conducts heat wellconducts heat wellMetals: silver, Metals: silver, copper, stainless copper, stainless steelsteel

InsulatorsInsulatorsA material that does A material that does

not conduct heat well.not conduct heat well.Wool, straw, paper, Wool, straw, paper, corkcork

Gases: airGases: air

Changes in StateChanges in StateThree states of Three states of mattermatterSolidSolidLiquidLiquidGasGas

Changes in StateChanges in State Physical change is a Physical change is a

change of state from one change of state from one form to anotherform to another

Most often occurs Most often occurs between solid & liquid; between solid & liquid; liquid & gasliquid & gas

Changes in StateChanges in StateMatter will change Matter will change

from one state to from one state to another if another if thermal thermal energyenergy is is absorbedabsorbed or or releasedreleased..

Changes in StateChanges in StateThe addition or loss of The addition or loss of

thermal energy changes thermal energy changes the arrangement of the the arrangement of the particles.particles.

The average kinetic The average kinetic energy DOES NOT energy DOES NOT change.change.

Changes in StateChanges in StateMelting:Melting: solid to solid to

liquidliquidMelting point:Melting point:

temperature at which temperature at which a solid changes to a a solid changes to a liquidliquid

Changes in StateChanges in State Freezing:Freezing: liquid to a solid liquid to a solid Freezing point:Freezing point: when a when a

substance loses thermal substance loses thermal energy; temperature at energy; temperature at which a liquid changes to which a liquid changes to a solida solid

Changes in StateChanges in State Vaporization:Vaporization: liquid to a liquid to a

gasgasEvaporation:Evaporation: at the at the

surfacesurfaceBoiling:Boiling: below the surface below the surfaceBoiling point:Boiling point: temperature temperature

at which liquid becomes a at which liquid becomes a gas (boils)gas (boils)

Changes in StateChanges in StateCondensation:Condensation: gas gas

becomes liquidbecomes liquid

Changes in StateChanges in State Thermal Expansion:Thermal Expansion:

expanding of matter when expanding of matter when it is heatedit is heatedAs thermal energy of a As thermal energy of a

substance increases, its substance increases, its particles spread out.particles spread out.

True even when a True even when a substance is not spreading substance is not spreading outout

Changes in StateChanges in State Examples of thermal Examples of thermal

expansion:expansion:ThermometerThermometerTeeth (fillings)Teeth (fillings)Thermostats (heat-Thermostats (heat-

regulating device)regulating device)

Uses of HeatUses of HeatHeat engineHeat engine

Conversion of thermal Conversion of thermal energy to mechanical energy to mechanical energy requires a heat energy requires a heat engineengine

Make use of Make use of combustion: burning combustion: burning fuel (coal, gasoline)fuel (coal, gasoline)

Heat EngineHeat Engine During combustion, During combustion,

chemical energy is chemical energy is converted to thermal converted to thermal energyenergy

Heat engine converts the Heat engine converts the thermal energy into thermal energy into mechanical energymechanical energy

Heat EngineHeat EngineClassified according to Classified according to

whether combustion whether combustion takes place outside the takes place outside the engine or inside the engine or inside the engineengine

Heat EngineHeat EngineExternal combustion External combustion

engineengineFuel is burned Fuel is burned

outside the engine.outside the engine.Steam engineSteam engine

Heat EngineHeat Engine Internal combustion Internal combustion

engineengineFuel is burned in Fuel is burned in

cylinders inside the cylinders inside the engineengine

Automobiles Automobiles