Pre-AP Physics Unit 6: Thermodynamics. “Thermodynamics”  Is derived from Greek meaning “movement of heat.”

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Pre-AP Physics Unit 6: Thermodynamics

“Thermodynamics”  Is derived from Greek meaning “movement of heat.”

The First Law of Thermodynamics  Official Definition: When heat flows in or out of a system, the energy it gains or loses is equal to the amount of heat transferred.  Or… Heat = Energy !  Is analogous to the Law of Conservation of Energy  We are now dealing with Internal Energy

Temperature:  What is it?  How “Hot” or “Cold” a substance is.  Temperature represents the average translational kinetic energy of the individual particles in a system.  The Temperature Scales  Fahrenheit – water freezes at 32 o F and boils at 212 o F  Celsius – Water freezes at 0 o C and boils at 100 o C  Kelvin – is based off of Absolute Zero  Absolute Zero  So cold that all particles stop moving!  Total energy of the particles is 0.

Temperature: 

Specific Heat Capacity  What is it?  The resistance to change in temperature of a substance.  The Equation:  Q = mcΔT  Examples:

The Second Law of Thermodynamics  Official Definition: Heat, of itself, never flows from a colder object to a warmer object.  Energy always flows from Hot to Cold  This law is also called the Law of Entropy

What is Entropy?  The amount of disorder in a system  The universe is always moving towards more entropy  Examples:  Ice melting  Liquid water evaporating  It takes Work (energy) to decrease Entropy

Types of Heat Transfer  Conduction  Heat transfer between materials that are in direct contact with each other.  Convection  Transfer in a fluid by movement of the substance itself.  Radiation  Energy transmitted by electromagnetic waves.

Phase Changes  The States of Matter:

Phase Changes  Types of Phase Changes:  Melting  Evaporation  Condensation  Boiling  Sublimation Melting Condensation Evaporation Boiling Sublimation

Phase Changes  How do you change the melting point or boiling point of a substance?  Add a solute  Change the pressure

Phase Changes  Energy During Phase Changes  What happens to the temperature of water as heat is added?  It Increases.  What happens to the temperature during a phase change?  It remains constant.

Phase Changes  Latent Heat  Latent Heat of Fusion  The amount of energy required to change a unit mass of any substance from a solid to a liquid (and vice versa).  Abbreviated L f (or H f )  Latent Heat of Vaporization  The amount of energy required to change a unit mass from liquid to gas (and vice versa).  Abbreviated L v (or H v ) LvLv LfLf

Phase Changes  Latent Heat  Equation: Q = mL Where: Q = heat added during phase change m = mass of sample L = Latent Heat (of fusion or vaporization)  Examples:

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