# Shared Flashcard Set

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Chapter 24: Thermodynamics Questions
Chapter 24: Thermodynamics Questions
19
Physics
01/05/2012

Term
 As disorder increases, entropy _______________________________
Definition
 increases
Term
 Define: entropy
Definition
 A measure of the disorder of a system. Energy allowed to transform freely goes to an energy form that has greater disorder (dissipated heat)
Term
Definition
 No heat enters or leaves a system when the system contracts or expands
Term
 A chunk of iron has a temperature of 0oC. If a second, identical chunk of iron is twice as hot (has twice the absolute temperature), what is its temperature in degrees Celsius?
Definition
 273oC. The 0oC iron has an absolute temperature of 273oK. When that is doubled, it is 547oK. Converting K to C, subtract 273o, so the temperature of the iron 2X as hot is 273oC.
Term
 Thermodynamics is the study of _____________ and ____________
Definition
 heat and work
Term
 Define: absolute zero
Definition
 When molecules have a minimum KE
Term
 If 10 J of energy is added to a system that does no external work, by how much will the internal energy of that system be raised?
Definition
 10 J
Term
 If 10 J of energy is added to a system that does 4 J of external work, by how much will the internal energy of that system be raised?
Definition
 6J. 10J-4J = 6J
Term
 State the first law of Thermodynamics.
Definition
 ∆Heat = ∆internal energy + workHeat added to a system = the increase in internal energy + external work done by the system.
Term
 The process of compression and expansion of gases in the cylinders of an automobile engine happen so quickly that the process is considered ___________________
Definition
 adiabatic. (Heat doesn’t have time to enter or leave the system so the energy becomes mostly work.)
Term
Definition
 No. When pressure↑, temp ↑ and When pressure ↓, temp↓ for an adiabatic process.
Term
 When diesel fuel is compressed in a diesel engine, the temperature gets so high the fuel __________________ combusts without a spark plug.
Definition
 spontaneously
Term
 Give me an equation for the adiabatic form of the 1st law of Thermodynamics.
Definition
 ∆T ≈ ∆P and ↑P≈↑T
Term
 What is a heat engine?
Definition
 Any device that changes internal energy into mechanical work.
Term
 State the second law of Thermodynamics.
Definition
 Heat will never of itself flow from a cold object to a hot object. No heat engine can convert all heat input into mechanical energy.
Term
 When you are dealing with changing internal energy into mechanical energy, is there always “heat exhaust”?
Definition
 yes. Heat exhaust is always produced when internal energy is changed into mechanical energy.
Term
 What is the common name for undesirable heat exhaust from a heat engine?
Definition
 Thermal pollution
Term
 Give me the equation for Carnot efficiency.
Definition
 Ideal efficiency = (Thot – Tcold) /Thot T must be in Kelvin
Term
 In Carnot’s equation, the greater the temperature differences between the input and output, the _____________ the efficiency.
Definition
 greater
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