Thermal Energy

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Thermal Energy

• Milbank High School

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Sec. 12.1Temperature and Thermal Energy

• Objectives
• Describe the nature of thermal energy
• Define temperature and distinguish it from
  thermal energy
• Use the Celsius and Kelvin temperature scales and
  convert one to the other
• Define specific heat and calculate heat transfer

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Thermodynamics

• The study of heat
• Kinetic-molecular theory
• Thermal Energy
• Overall energy of motion of the particles that
  make up an object
• Temperature

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Equilibrium/Thermometry

• Conduction
• Thermal Equilibrium
• Thermometer

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Celsius and Kelvin

• Celsius
• Water freezes at 0C
• Boils at 100C
• Kelvin
• Water freezes at 273 K
• Absolute Zero
• -273C
• 0 K

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Heat and Thermal Energy

• Heat
• The energy that flows between two objects as a
  result of a difference in temperature (Q)
• Measured in Joules (energy)
• Convection
• Radiation
• Specific Heat
• Q mC?T

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Calorimetry

• A device used to measure changes in thermal
  energy
• Insulated
• Conservation of Energy in a closed system
• Example Problem
• Heat Transfer in a Calorimeter

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Review Concepts

• Temperature is proportional to the average
  ________________of its particles.
• Thermal energy is the measure of ______________.
• At absolute zero, ________________.
• Can you take the temperature inside of a vacuum?
• Which liquid would an ice cube cool faster, water
  or methanol?
• Why do easily vaporized liquids, such as acetone
  and methanol, feel cool to the skin?

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Sec. 12.2Change of State and Laws of
Thermodynamics

• Objectives
• Define heats of fusion and vaporization
• State the first and second laws of thermodynamics
• Define heat engine, refrigerator, and heat pump
• Define entropy

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Change of State

• Melting point
• Boiling point
• Heat of fusion
• Q mHf
• Heat of vaporization
• Q mHv
• Example Problem
• Melting a Solid and Warming the Resulting Liquid

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The First Law of Thermodynamics

• 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
• Heat Engine

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Refrigeration
Refrigeration-- Cooling by evaporation.
Compress cool to liquefy a gas (outside the
fridge) then boil it in a vacuum (inside the
fridge) to absorb heat.
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The Second Law of Thermodynamics

• Entropy
• Natural processes go in a direction that
  maintains or increases the total entropy on the
  universe
• Things become more disordered

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Review Concepts

• Can you add thermal energy to an object without
  increasing its temperature?
• When wax freezes, is energy absorbed or released
  by the wax?
• You are boiling pasta. Will it cook faster if
  the water is boiling vigorously or if it is
  boiling gently?

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Review

• The second law of thermodynamics states that
  natural processes go in a direction that
  maintains or increases total __________.
• First law of thermodynamics says that _________
  ____________________
• Heat of fusion
• Heat of vaporization
• The three types of thermal energy transfer are
  _________, _________, and _________.

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Review

• Entropy!
• How does it relate to creation/evolution?
• The entropy of the universe always ___________
  (increases or decreases).
• An internal combustion engine converts
  _________energy to ________ energy.
• _________ ________ is the quantity of heat
  required to raise the temperature of one kilogram
  of a substance by one kelvin.

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Review

• What does the kinetic-molecular theory state?
• _______________is the study of heat.
• When using a thermometer, energy is transferred
  via a process called ____________.