Electromagnetic Induction and Power Transmission Physics Montwood High School R. Casao.
Latent Heat Physics Montwood High School R. Casao.
-
Upload
garey-ryan -
Category
Documents
-
view
217 -
download
0
Transcript of Latent Heat Physics Montwood High School R. Casao.
![Page 1: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/1.jpg)
Latent Heat
Physics
Montwood High School
R. Casao
![Page 2: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/2.jpg)
Change of StateMatter exists in 3 states:
•Solid
•Liquid
•Gas
water steam
fusion (at melting point)
vaporization (takes place at boiling point)
solidification condensation
Consider water:
at freezing point at boiling point
ice
![Page 3: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/3.jpg)
Heats of Transformation
When energy is absorbed as heat by a solid or liquid, the temperature of the object does not necessarily rise.
The thermal energy may cause the mass to change from one phase, or state, to another.
The amount of energy per unit mass that must be transferred as heat when a mass undergoes a phase change is called the heat of transformation, L.
![Page 4: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/4.jpg)
Heat of Fusion To melt a solid means to change its
from the solid state to the liquid state. This process requires energy because the molecules of the solid must be freed from their rigid structure.
To freeze a liquid to form a solid is the reverse of melting and requires that energy be removed from the liquid so that the molecules can settle into a rigid structure.
![Page 5: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/5.jpg)
Heat of Fusion When the phase change is from
solid to liquid, the sample must absorb heat; when the phase change is from a liquid to solid, the sample must release heat.
The heat of transformation for these phase changes is called the heat of fusion, Lf.
Water: Lf = 334 J/g = 79.5 cal/g
fLmQ
![Page 6: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/6.jpg)
Heat of Vaporization To vaporize a liquid means to change it from the
liquid state to the vapor or gas state. This process requires energy because the molecules must be freed from the liquid state.
Condensing a gas to a liquid is the reverse of vaporizing; it requires that energy be removed from the gas so that the molecules can cluster together instead of flying away from each other.
The heat of transformation for these phase changes is called the heat of vaporization, Lv.
Water: Lv = 2256 J/g = 539 cal/g
vLmQ
![Page 7: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/7.jpg)
Phase Changes
![Page 8: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/8.jpg)
Copyright 1999, PRENTICE HALL
Chapter 118
Gas-Liquid Equilibration
![Page 9: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/9.jpg)
![Page 10: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/10.jpg)
Copyright 1999, PRENTICE HALL
Chapter 1110
Phase ChangesPhase Changes
Energy Changes Accompanying Phase Energy Changes Accompanying Phase ChangesChanges
![Page 11: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/11.jpg)
![Page 12: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/12.jpg)
Copyright 1999, PRENTICE HALL
Chapter 1112
Phase ChangesPhase Changes
Heating CurvesHeating Curves
![Page 13: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/13.jpg)
Copyright 1999, PRENTICE HALL
Chapter 1113
Heating Curve Illustrated
![Page 14: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/14.jpg)
![Page 15: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/15.jpg)
![Page 16: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/16.jpg)
Phase Change Diagram - Water
![Page 17: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/17.jpg)
vaporization
energy in
2260 kJ
fusion
energy in
334 kJ
condensation
energy out
2260 kJ
solidification
energy
out 334 kJ
steam(1 kg)
water(1 kg)
ice(1 kg)
Summary: Change of State
![Page 18: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/18.jpg)
Energy involved in heating 1 kg of water
icesteam(ice and water) melting
(334) (420)water
boiling
(water and stream)(2260) energy /
kJ
Summary: from ice to steam
0
100
![Page 19: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/19.jpg)
Heat of Combustion (HC)
The amount of heat released per unit mass or unit volume of a substance when the substance is completely burned.
Heats of combustion are used as a basis for comparing the heating value of fuels, since the fuel that produces the greater amount of heat for a given cost is the more economic.
Equation:
CHmQ
![Page 20: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/20.jpg)
Phase Change Example Heat is added to 0.5 kg of water at 20° C.
How many joules of heat energy are required to change the water to steam at 110° C?
Heat has to be added to the water to raise its temperature from 20° C to the boiling point 100° C.
Heat has to be added to vaporize all of the water that is at 100° C.
JQ
CCCkg
JkgTcmQ oo
o
167440
2010041865.0
![Page 21: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/21.jpg)
Phase Change Example
Heat has to be added to raise the temperature of all of the steam from 100° C to 110° C.
Total heat energy: Q = 167440 J + 1130000 J + 10050 J = 1307490 J
J1130000Q
kgJ
2260000kg5.0LvmQ
J10050Q
C100C110Ckg
J2010kg5.0TcmQ oo
o
![Page 22: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/22.jpg)
Final Temperature Example A 0.3 kg piece of ice at 0° C is placed in 1 kg of
water at 40° C in an insulated container. If no heat is lost to the container, what is the final temperature of the water?
Q lost water = Q gained ice + Q gained ice water (m·c·T)water = m·Lf + (m·c·T)ice water
FFo
oFo
Fo
o
TkgJ
1255.8J100200TCJ
4186J167440
C0TCkg
J4186kg0.3
kgJ
334000kg0.3TC40Ckg
J4186kg1
![Page 23: Latent Heat Physics Montwood High School R. Casao.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649e705503460f94b6eca9/html5/thumbnails/23.jpg)
Final Temperature Example
C.
CJ
5441.8
JT
TCJ
5441.8J
TCJ
4186TCJ
1255.8J100200J167440
o
o
F
Fo
FoFo
4251267240
67240