Heat and Heat and TemperatureTemperature

Chapter 16Chapter 16

P. Sci.

Unit 4 cont.

What is What is Temperature?Temperature?•Particles Particles (atoms and (atoms and

molecules)molecules) within a within a substance are substance are constantly moving constantly moving (kinetic energy)(kinetic energy)

•Temperature is the Temperature is the measure of the measure of the average kinetic average kinetic energy in an objectenergy in an object

What is Temperature What is Temperature cont.cont.

•As kinetic energy As kinetic energy increases, temperature increases, temperature increases.increases.

•Thermometers- expand Thermometers- expand as temperature as temperature increases and contracts increases and contracts as temperature as temperature decreases.decreases.

Measuring Measuring TemperatureTemperature

Units for Units for temperature temperature can be can be

•Celsius Celsius (centigrade)(centigrade)

•FahrenheitFahrenheit•KelvinKelvin

FahrenheitFahrenheit

•American scale – American scale – not used in sciencenot used in science

•For WaterFor Water–Freezing point: 32Freezing point: 32°F°F–Boiling point: 212°FBoiling point: 212°F

CelsiusCelsius •Also known as Also known as CentigradeCentigrade

•For waterFor water–Freezing point: Freezing point: 00°C°C

–Boiling point: Boiling point: 100°C100°C

•1°C= about 2°F1°C= about 2°F

KelviKelvinn

•SI unit to measureSI unit to measure

temperaturetemperature

•0 K is absolute zero=0 K is absolute zero=

-273.13 -273.13 °C°C

•Energy is minimal Energy is minimal and and

cannot go any lowercannot go any lower

Temperature ConversationTemperature Conversation K = °CK = °C + 273+ 273

°F = (9/5x °C) +32 °F = (9/5x °C) +32 °C = 5/9(°F-32) °C = 5/9(°F-32)

• Convert 58 °C to KConvert 58 °C to K

• Convert 58 °C to °FConvert 58 °C to °F

• Convert 358 K to °CConvert 358 K to °C

Energy Energy TransferTransfer

•Temperature is Temperature is energy transferred energy transferred as heatas heat

•Energy must move Energy must move for heat to occur.for heat to occur.

Energy Transfer cont.Energy Transfer cont.•Heat: transfer of Heat: transfer of

energy between the energy between the particles of 2 objects particles of 2 objects due to temperature due to temperature difference.difference.

•Heat flows from high Heat flows from high temperature temperature (energy) to low (energy) to low temperature temperature (energy)(energy)

Examples of energy Examples of energy transfertransfer•Freezing water for iceFreezing water for ice

•Dew evaporating in Dew evaporating in morning sunlightmorning sunlight

•Heating water for a Heating water for a showershower

Types of Energy Types of Energy TransferTransfer

1. 1. Conduction:Conduction: direct contact; direct contact; 2 objects in 2 objects in contact are at contact are at unequal unequal temperaturestemperatures

2. Convection:2. Convection:

movement of movement of warm fluids.warm fluids.

Movement of the Movement of the heated substance (liquid heated substance (liquid or gas)or gas)Convection Current: cycle Convection Current: cycle

of a heated fluid that rises, of a heated fluid that rises, cools, and fallscools, and falls

3. Radiation3. Radiation: no physical : no physical contact needed.contact needed.

Transfer of energy Transfer of energy through through electromagnetic electromagnetic waves (infrared, waves (infrared, visible light, visible light, ultraviolet)ultraviolet)No movement of No movement of mattermatter

–Example: standing in Example: standing in sunlightsunlight

Which type of heat transfer is Which type of heat transfer is illustrated below?illustrated below?

C

Conductors Conductors

•Any material Any material through which through which energy is energy is easily easily Transferred.Transferred.

•Usually solid metals Usually solid metals because their because their molecules are tightly molecules are tightly packed.packed.

•Gases and liquids are Gases and liquids are poor conductors poor conductors because the because the molecules are not as molecules are not as tightly packed tightly packed together.together.

InsulatorsInsulators•Slow down Slow down

heat transferheat transfer

•Poor Poor conductorsconductors

•Examples: Examples: rubber or rubber or woodwood

Specific HeatSpecific Heat•The amount of energy needed to The amount of energy needed to

raise 1kg of a substance by 1 Kraise 1kg of a substance by 1 K Q= cmQ= cmΔΔtt

– Q = heatQ = heat– c = specific heatc = specific heat– m= massm= mass– ΔΔt= change in temperaturet= change in temperature

•ΔΔt = final Temp – initial temp t = final Temp – initial temp –SI unit is Joules (J)SI unit is Joules (J)

Specific Heat CalculationsSpecific Heat Calculations

•Aluminum has a specific heat of Aluminum has a specific heat of 0.902 J/kg x 0.902 J/kg x °C°C.   How much heat .   How much heat is lost when a piece of aluminum is lost when a piece of aluminum with a mass of 23.984 kg cools with a mass of 23.984 kg cools from a temperature of 415.0 from a temperature of 415.0 °C°C to a temperature of 22.0 to a temperature of 22.0 °C°C? ?

Specific Heat CalculationsSpecific Heat Calculations1. How much heat is required to warm

275 kg of water from 76 °C°C to 87 °C°C? (specific heat of water is 4.179 J/g °C)°C)

•Remember…Remember…– energy is alwaysenergy is always

conserved.conserved.– Energy is transferred Energy is transferred

from higher temperatures to from higher temperatures to lower temperatures.lower temperatures.

– Insulation minimizes Insulation minimizes unwanted energy transfers unwanted energy transfers in walls, attics, etc.in walls, attics, etc.

Energy Transformations in Energy Transformations in IllustrationsIllustrations

Bouncing BallBouncing Ball• When dropping a ball it travels the When dropping a ball it travels the

following path where is thefollowing path where is theKinetic energy is decreasingKinetic energy is decreasingKinetic energy is increasingKinetic energy is increasingKinetic energy is the HIGHESTKinetic energy is the HIGHESTKinetic energy is the LOWESTKinetic energy is the LOWESTPotential energy is decreasingPotential energy is decreasingPotential energy is increasingPotential energy is increasingPotential energy is the HIGHESTPotential energy is the HIGHESTPotential energy is the LOWESTPotential energy is the LOWESTBoth KE and PE presentBoth KE and PE present

PendulumPendulum• A pendulum travels the following path A pendulum travels the following path

where is thewhere is theKinetic energy is decreasingKinetic energy is decreasingKinetic energy is increasingKinetic energy is increasingKinetic energy is the HIGHESTKinetic energy is the HIGHESTKinetic energy is the LOWESTKinetic energy is the LOWESTPotential energy is decreasingPotential energy is decreasingPotential energy is increasingPotential energy is increasingPotential energy is the HIGHESTPotential energy is the HIGHESTPotential energy is the LOWESTPotential energy is the LOWESTBoth KE and PE presentBoth KE and PE present

Reading Specific Heat TablesReading Specific Heat Tables• Recall specific heat tells Recall specific heat tells

you how much energy is you how much energy is needed to increase the needed to increase the temperature of 1 gram by temperature of 1 gram by 1 degree.1 degree.– What substance takes the What substance takes the

most energy to heat?most energy to heat?– What substance take the What substance take the

least energy to heat?least energy to heat?– What two substances listed What two substances listed

make good conductors?make good conductors?– What two substances make What two substances make

good insulators?good insulators?

K = °CK = °C + 273+ 273

°F = (9/5x °C) +32 °F = (9/5x °C) +32 °C = 5/9(°F-32) °C = 5/9(°F-32)

Kinetic Energy =1/2 (mass x velocityKinetic Energy =1/2 (mass x velocity22))

KE = ½ m vKE = ½ m v22

Potential Energy = mass x gravity x Potential Energy = mass x gravity x heightheight

PE = m g hPE = m g h

g = 9.8 m/sg = 9.8 m/s22

Heat = mass x specific heat x change in Heat = mass x specific heat x change in temptemp

Q = m c Q = m c ΔΔtt

ReviewReview1.1.What is temperature?What is temperature?

2.2.Name the 3 different Name the 3 different scales with which scales with which temperature is measured.temperature is measured.

3.3.Convert 51Convert 51°C to Kelvin°C to Kelvin..

4.4.Convert 324K to Convert 324K to Celsius.Celsius.

5.5.Name 3 methods of Name 3 methods of energy transfer and energy transfer and explain how they explain how they work.work.

6.6.Explain the difference Explain the difference between conductors between conductors

and insulatorsand insulators

Unit 4 Equations Unit 4 Equations K = °CK = °C + 273+ 273°F = (9/5x °C) +32 °F = (9/5x °C) +32 °C = 5/9(°F-32)°C = 5/9(°F-32)Kinetic Energy =1/2 (mass x velocityKinetic Energy =1/2 (mass x velocity22))

KE = ½ m vKE = ½ m v22

Potential Energy = mass x gravity x heightPotential Energy = mass x gravity x heightPE = m g hPE = m g h

g = 9.8 m/sg = 9.8 m/s22

Heat = mass x specific heat x change in Heat = mass x specific heat x change in temptemp

Q = m c Q = m c ΔΔttΔΔt = final temp – initial tempt = final temp – initial temp