Heat, Temperature, Heat Transfer, Thermal Expansion & Thermodynamics

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1. Heat, Temperature, Heat Transfer, Thermal Expansion & Thermodynamics
2. Heat vs. TemperatureHeatA form of energyMeasured in
3. Heat Transfer Conduction - requires direct contact
4. Thermal EquilibriumA system is in thermal equilibrium
5. Temperature ScalesThere are four temperature scales –
6. Comparing Temperature ScalesFreezing = 0°C = 273
7. Change of StateTemp ° CIncreasing Heat Energy
8. Specific HeatThe amount of heat energy needed
9. Latent Heat (Latent) Heat of fusion –
10. Heat CalculationsQ = mcΔTTemperature ChangeQ = heat
11. Melting & Boiling PointMelting or Freezing Point
12. Thermal ExpansionSubstances expand as they heat and
13. Thermal Expansion - LinearΔLLinear expansion: objects expand
14. Thermal Expansion (Volume) Volume expansion: since objects
15. ThermodynamicsThe study of changes in thermal properties
16. 1st Law of ThermodynamicsThe total increase in
17. Heat enginesConvert thermal energy to mechanical energyRequire
18. Refrigerators and Heat PumpsIt is possible to
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Heat vs. TemperatureHeatA form of energyMeasured in calories or Joules There is no “coldness” energyAny object with temperature above zero Kelvin has heat energyTemperatureAvg. Kinetic Energy of the particlesMeasured in C,

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Heat, Temperature, Heat Transfer, Thermal Expansion & Thermodynamics

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Слайд 1Heat, Temperature, Heat Transfer, Thermal Expansion & Thermodynamics

Слайд 2Heat vs. Temperature
Heat
A form of energy
Measured in calories or Joules

There is no “coldness” energy
Any object with temperature above zero

Kelvin has heat energy

Temperature
Avg. Kinetic Energy of the particles
Measured in C, F, K
“hot” & “cold are relative terms
Absolute zero is zero Kelvin

Heat vs. TemperatureHeatA form of energyMeasured in calories or Joules There is no “coldness” energyAny object with

Слайд 3Heat Transfer
Conduction - requires direct contact or

particle to particle transfer of energy; usually occurs

in solids
Convection - heat moves in currents; hot air rises and cold air falls; only occurs in fluids
3.Radiation - heat waves travel through empty space, no matter needed; sun

Heat Transfer Conduction - requires direct contact or particle to particle transfer

Слайд 4Thermal Equilibrium
A system is in thermal equilibrium when all of

its parts are at the same temperature.
Heat transfers only from

high to low temperatures and only until thermal equilibrium is reached.

Thermal EquilibriumA system is in thermal equilibrium when all of its parts are at the same temperature.Heat

Слайд 5Temperature Scales
There are four temperature scales – Celsius (Centigrade), Kelvin,

Fahrenheit
Celsius, C – metric temp. scale
Fahrenheit, F – customary (english)

temp. scale
Kelvin, K – metric absolute zero temp. scale
Rankine, R – english absolute temp. scale

Temperature ScalesThere are four temperature scales – Celsius (Centigrade), Kelvin, FahrenheitCelsius, C – metric temp. scaleFahrenheit, F

Слайд 6Comparing Temperature Scales
Freezing = 0°C = 273 K = 32°F
Boiling

= 100°C = 373 K = 212 °F

Conversions between Scales
°F

= 1.8 x°C+32 = 9/5 °C + 32
°C = (°F – 32) / 1.8 = 5/9 (°F – 32)
K = °C + 273 or °C = K - 273

(All temperatures listed are for water)

Comparing Temperature ScalesFreezing = 0°C = 273 K = 32°FBoiling = 100°C = 373 K = 212

Слайд 7Change of State
Temp ° C
Increasing Heat Energy (Joules)
-20
100
0
ice
water
steam
melting
vaporization
condensation
freezing
As heat is

added to a substance it will either be absorbed to

raise the temperature OR to change the state of matter.
It can NEVER do both at the same time!
Temperature will NOT change during a phase change!

Heat of vaporization

Heat of fusion

Change of StateTemp ° CIncreasing Heat Energy (Joules)-201000icewatersteammeltingvaporizationcondensationfreezingAs heat is added to a substance it will either

Слайд 8Specific Heat
The amount of heat energy needed to raise the

temperature of 1 gram (or kg) of a substance by

1°C (or 1 K).
Substances with higher specific heats, such as water, change temperature more slowly.

Symbol : c units : cal/(g°C) or J/(kg°C)

For water: c = 4.186 J/(g°C) = 4186 J/(kg°C)
or c = 1 cal/ (g°C)

Specific HeatThe amount of heat energy needed to raise the temperature of 1 gram (or kg) of

Слайд 9Latent Heat
(Latent) Heat of fusion – the heat energy

needed to melt (solid→liquid) or freeze (liquid → solid)

one gram (or kg) of a substance. For water: Hf =334,000 J/kg or 80 cal/g

(Latent) Heat of vaporization – the heat energy needed to vaporize (liquid→gas) or condense (gas→liquid) one gram (or kg) of a substance. For water: Hv = 2.26 x 105 J/kg or 540 cal/g

Latent Heat (Latent) Heat of fusion – the heat energy needed to melt (solid→liquid) or freeze

Слайд 10Heat Calculations
Q = mcΔT
Temperature Change
Q = heat absorbed or released,

J
m = mass of substance being heated, kg
c = specific

heat of substance, J/(kg°C)
ΔT = change in temp.,°C or K

Phase Change

Q = mHf Q = mHv

Q = heat absorbed or released
m = mass of substance changing phase, kg
Hf = heat of fusion, J/kg (liquid solid)
Hv = heat of vaporization, J/kg
J/kg (liquid gas)

Heat CalculationsQ = mcΔTTemperature ChangeQ = heat absorbed or released, Jm = mass of substance being heated,

Слайд 11Melting & Boiling Point
Melting or Freezing Point – the temperature

at which a substance melts or freezes. Water: 0°C
Boiling or

Condensation Point – the temperature at which a substance vaporizes or condenses. Water: 100°C
For other substances, refer to your chart.

Melting & Boiling PointMelting or Freezing Point – the temperature at which a substance melts or freezes.

Слайд 12Thermal Expansion
Substances expand as they heat and contract as they

cool.
The rate of expansion depends on the substance’s coefficient of

expansion ( α for linear, β for volume)
The exception to this rule is water. As water is cooled from 4°C to 0°C, it expands which explains why ice floats (it is less dense than water).

Thermal ExpansionSubstances expand as they heat and contract as they cool.The rate of expansion depends on the

Слайд 13Thermal Expansion - Linear
ΔL
Linear expansion: objects expand along linear dimensions

such as length, width, height, diameter, etc.
ΔL = Loα ΔT

LF = L0 + ΔL

ΔL = change in length measurement, (same units as original length)
Lo = original length, (any length unit – m, cm, in)
ΔT = change in temperature (°C) = Tf – Ti
α = coefficient of linear expansion (1 / °C or °C -1 )
LF = final length, (same units as original length)

Thermal Expansion - LinearΔLLinear expansion: objects expand along linear dimensions such as length, width, height, diameter, etc.ΔL

Слайд 14Thermal Expansion (Volume)
Volume expansion: since objects expand in all dimensions,

volume also expands.
ΔV = Voβ ΔT VF =

VO + ΔV

ΔV = change in volume (same units as original volume)
Vo = original volume, (any volume units – L, mL, cm3 )
ΔT = change in temperature (°C) = Tf – Ti
β = coefficient of volume expansion (1 / °C or °C -1 )
VF = final volume, (same units as original)

Thermal Expansion (Volume) Volume expansion: since objects expand in all dimensions, volume also expands.ΔV = Voβ ΔT

Слайд 15Thermodynamics
The study of changes in thermal properties of matter
Follows Law

of Conservation of Energy
1st Law – the total increase in

the thermal energy of a system is the sum of the work done on it and the heat added to it
2nd Law – natural processes tend to increase the total entropy (disorder) of the universe.

ThermodynamicsThe study of changes in thermal properties of matterFollows Law of Conservation of Energy1st Law – the

Слайд 161st Law of Thermodynamics
The total increase in the thermal energy

of a system is the sum of the work done

on it and the heat added to it.

ΔU = W + Q

ΔU = change in the thermal energy of the system
W = work done on the system (W = Fd or W=ΔK)
Q = heat added to the system
(Q is + if absorbed, Q is – if released)
*All measured in Joules*

1st Law of ThermodynamicsThe total increase in the thermal energy of a system is the sum of

Слайд 17Heat engines
Convert thermal energy to mechanical energy
Require high temp heat

source and low temp heat sink. (Takes advantage of heat

transfer process)
Examples: Steam engine, Automobile engine

Heat enginesConvert thermal energy to mechanical energyRequire high temp heat source and low temp heat sink. (Takes

Слайд 18Refrigerators and Heat Pumps
It is possible to remove heat from

a cold environment and deposit it into a warmer environment.
This

requires an outside source of energy.
Examples: Refrigerators, Air conditioning units
Heat pumps are refrigeration units that work in either direction.

Refrigerators and Heat PumpsIt is possible to remove heat from a cold environment and deposit it into

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Heat, Temperature, Heat Transfer, Thermal Expansion & Thermodynamics

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Слайды и текст этой презентации

Слайд 1Heat, Temperature, Heat Transfer, Thermal Expansion & Thermodynamics

Слайд 2Heat vs. TemperatureHeatA form of energyMeasured in calories or Joules

There is no “coldness” energyAny object with temperature above zero

Слайд 3Heat Transfer Conduction - requires direct contact or

particle to particle transfer of energy; usually occurs

Слайд 4Thermal EquilibriumA system is in thermal equilibrium when all of

its parts are at the same temperature.Heat transfers only from

Слайд 5Temperature ScalesThere are four temperature scales – Celsius (Centigrade), Kelvin,

FahrenheitCelsius, C – metric temp. scaleFahrenheit, F – customary (english)

Слайд 6Comparing Temperature ScalesFreezing = 0°C = 273 K = 32°FBoiling

= 100°C = 373 K = 212 °FConversions between Scales°F

Слайд 7Change of StateTemp ° CIncreasing Heat Energy (Joules)-201000icewatersteammeltingvaporizationcondensationfreezingAs heat is

added to a substance it will either be absorbed to

Слайд 8Specific HeatThe amount of heat energy needed to raise the

temperature of 1 gram (or kg) of a substance by

Слайд 9Latent Heat (Latent) Heat of fusion – the heat energy

needed to melt (solid→liquid) or freeze (liquid → solid)

Слайд 10Heat CalculationsQ = mcΔTTemperature ChangeQ = heat absorbed or released,

Jm = mass of substance being heated, kgc = specific

Слайд 11Melting & Boiling PointMelting or Freezing Point – the temperature

at which a substance melts or freezes. Water: 0°CBoiling or

Слайд 12Thermal ExpansionSubstances expand as they heat and contract as they

cool.The rate of expansion depends on the substance’s coefficient of

Слайд 13Thermal Expansion - LinearΔLLinear expansion: objects expand along linear dimensions

such as length, width, height, diameter, etc.ΔL = Loα ΔT

Слайд 14Thermal Expansion (Volume) Volume expansion: since objects expand in all dimensions,

volume also expands.ΔV = Voβ ΔT VF =

Слайд 15ThermodynamicsThe study of changes in thermal properties of matterFollows Law

of Conservation of Energy1st Law – the total increase in

Слайд 161st Law of ThermodynamicsThe total increase in the thermal energy