Chapter 12
Thermal Energy
12.1- Temperature and Thermal
Energy
• Thermodynamics- the study of heat
transformations into other forms of energy
– began with 18th century steam engines
Thermal Energy
• Thermal Energy- total energy of a molecule
– From this the average energy per molecule can be
calculated
Hot Objects
• What will happen to this balloon if it is placed
in a refrigerator? What about over a pot of
boiling water?
Solids
• Particles cannot move freely- Vibrate
Thermal Energy and Temperature
• Group 1
• Temperature- depends on the average kinetic
energy of particles; does not depend on mass
• How much energy would a 2 kg block have to
have compared to 1 kg block at the same
temperature?
• Energy DOES depend on mass
•
Average Kinetic Energy per particle= Total Kinetic Energy/ Number of Particle
Equilibrium and Thermometry
• Conduction- transfer of kinetic energy when
particles collide
Thermal Equilibrium
• Thermal Equilibrium- the state in which the
rate of energy flow between the two objects is
equal and the objects are at the same
temperature
• Thermometers: GROUP 2
Temperature Scales
• Celsius- developed with
water in mind
• Kelvin- no negative
temperatures
• TC+273=TK
• Temperature limits
– No upper limit
– Lower limit is absolute zero
(-273.15 oC)
Heat and Flow of Thermal Energy
• Heat- energy that is
transferred between
objects
– Always flows from hot to
cold
• Conduction and
Convection- GROUP 3
• RADIATION- GROUP 4
Specific Heat
• The amount the
temperature increases
depends on the mass
and type of object.
• The amount of energy
that must be added to
the material to raise the
temperature of a unit
mass by one
temperature unit.
• J/kg K
• Table 12-1 page 318
• Heat Transfer Q=mC∆T
– Heat transfer is equal to the mass of an object
times the specific heat of the object times the
difference between the final and initial
temperatures.
Math Examples
Calorimetry: Measuring Specific Heat
• Calorimeter-device
used to measure
changes in thermal
energy
• Tf=mACATA + mBCBTB
mACA + mBCB
Math Practice
12.2 Changes of State and the Laws of
Thermodynamics
• Changes of State
– As the thermal energy of an object increases, the
motion of the particles __________, and the
temperature __________.
Melting Point
• Change from a solid to a liquid
– All energy goes to break forces between particles.
– No energy increase KE
– Temperature ____________________.
Boiling Point
• Change from a liquid to a gas
– Temperature ____________________.
Heat of Fusion
• Amount of energy needed to melt 1 kg of a
substance
• Q=mHf
Heat of Vaporization
• Thermal energy needed to vaporize 1 kg of a
liquid
• Q=mHv
• What would the equation be for the freezing
of a substance?
Math Examples
• You will have all day on Thursday to work on
Book Work, the Laboratory Analysis, or the
Chapter 12 Study Guide.
•
•
•
•
Friday we will finish Chapter 12 Notes
Monday we be doing another lab.
Tuesday we will grade the Study Guides
Test Wednesday
•
•
•
•
1st Law of
Thermodynamics
Heat Engines
Efficiency
Refrigerators
Heat Pumps
2nd Law of
Thermodynamics
• Entropy
• Violations of the 2nd Law