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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
Thermodynamics
• “The study of heat”
• Kinetic-molecular theory
• Thermal Energy– Overall energy of motion of the particles
that make up an object
• Temperature
Celsius and Kelvin
• Celsius– Water freezes at 0°C– Boils at 100°C
• Kelvin– Water freezes at 273 K
• Absolute Zero– -273°C– 0 K
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 = mCΔT
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
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?
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
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
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
RefrigerationRefrigeration-- Cooling by evaporation. Compress & cool to liquefy a gas (outside the fridge) then boil it in a vacuum (inside the fridge) to absorb heat.
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
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?
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 _________.
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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