Thermodynamics
Phase Change
• Three states of matter (Solid, liquid, gas)
• With increase in thermal energy a
substance can
– Increase temp or
– Change phase
• Draw phase change diagram
• Evaporation:
– Adding energy to a liquid until a phase change to gas.
• Condensation:
– Humidity is the amount of water vapor contained in the air.
Saturation is the point when the air cannot hold any more water.
• Sublimation/ dissolution
– Changing phase by skipping liquid phase.
Zeroth Law
• When two objects of dissimilar temp come
into contract heat transfer occurs.
1st Law
• When heat flows from a system, the
system gains or loses an amount of
energy equal to the amount transferred.
• Heat Added = increase in Internal Energy
+ Work
• Gas-Piston-Cylinder
– Adiabatic system. No heat is lost to the
enviroment.
2nd Law
• Heat of itself never flows from a cold
object to a hot object.
• Work is required to make heaters and AC
work. (example: opening a C02 cylinder)
• Perpetual motion of the 2nd kind.
3rd Law
• There is no temperature below Absolute
Zero.
Efficacy
• Efficacy defines how much work was
done.
• Describe a 4 stroke combustion engine.
Entropy – a measure of disorder
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Order tends to become disorder.
Higher Quality energy (i.e. Chemical).
useful energy turns in thermal energy.
Thermal energy is dissipated across the
universe.