B4

• internal energy


  the sum of the kinetic energy and the potential energy
• open system


  a system that can exchange thermal energy, work and matter with its surroundings
• closed system


  a system that can exchange thermal energy or work with its surroundings, but not matter
• isolated system


  a system that cannot exchange energy, work or matter with its surroundings
• isobaric process


  a process occurring at the gas with constant pressure
• isovolumetric process


  a process occuring at the gas with constant volume
• isothermal process


  a process occuring at the gas with constant temperature
• adiabatic process


  no thermal energy transfer between the gas and its surroundings in this process
• Entropy


  a thermodynamic quantity that relates to the degree of disorder of the particles in a system
• microstate


  a specific molecular configuration
• macrostate


  a larger-scale, measurable outcome, resulting from the outcome of each of the smaller microstates
• spontaneously


  one that occurs on its own, without any energy input from the outside
• heat engine


  a device which converts heat into useful mechanical energy
• the clausius statement


  It is impossible to construct a device which works on a cycle and produces no effect other than heat transfer from a cool body to a hot body
• the kelvin statement


  it is impossible to devise a heat engine that takes heat from the hot reservoir ( Q H ) and converts all the energy into useful external work without losing heat to the cold reservoir ( Q C )
• high entropy = high disorder
• the first law of thermodynamics


  The thermal energy entering a closed system is equal to the sum of the change in internal energy of the system and the work done by the system.
• the second law of thermodynamics

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• when Q is positive, thermal energy is supplied to the gas
• when Q is negatice, thermal energy is removed from the gas
• when the △U is positive, there is an increase in internal energy (kinetic energy increased, temperature increased)
• when the △U is negative, there is an decrease in internal energy (kinetic energy decreased, temperature decreased)
• when W is positive, work is being done by the gas (expansion)
• when W is negative, work is being done on the gas (compression)
• for isothermal process, △U = zero

  no change in temp = no change in KE
• for adiabatic process, Q is always zero
• adiabatic expansion results in cooling
• adiabatic compression results in heating
• there is no change in entropy in a carnot cycle
• a carnot cycle is an reversible heat engine
• Second Law of Thermodynamics

  The total entropy of an isolated system always increases over time
• Entropy (S)


  A measure of disorder or randomness in a system
• Enthalpy (H)


  A measure of the total energy of a system, including internal energy and the energy associated with the pressure and volume of a system
• Heat (Q)


  Energy transferred from one body to another due to a temperature difference
• Work (W)


  Energy transferred from one body to another due to a force applied over a distance
• Carnot Efficiency


  The maximum possible efficiency of a heat engine, given by η = 1 - (Tc/Th)
• Thermal Efficiency


  The ratio of the work output to the heat input, given by η = W/Q
• adiabatic process happens quickly = there isn't sufficient time for heat to be exchanged between the surroundings and the gas
• when the process is irreversible, entropy is increasing throughout the process