week 1 Flashcards
what is a system in thermodynamic
system is a universe defined by a boundary
what is a boundary in thermodynamic
this can be an actual or imaginary limitation of an area
what is a control volume in thermodynamic
if a boundary is fixed, then it is controlled via ‘control volume’
what is a surrounding in thermodynamic
what is outside the actual system
what are the types of systems called (2)
open and closed systems
what is an open system?
one where mass many enter or leave the system (in this case at the same rate, not gathering more mass)
what is the difference between gas constant and universal gas constant
gas constant is depending on the substance
the universal gas constant depends on nature
what is the difference between gas constant and universal gas constant
gas constant is depending on the substance
the universal gas constant depends on nature (always constant)
what is molar mass
this is mass of a given chemical element or compound divided by the amount of substance
what is the equation for 1st law of thermodynamics (energy transfer into our out of system )
Q - W = (Change in) U
heat transfer - work done = change in internal energy
how many independent parameters of state does air have
2 independent parameters
pressure and volume or pressure and temperature
temperature and volume and so on…..
different combinations but only 2 can be used to describe the air
the equation to find the perfect gas
the equation of state:
pressure = desnity X gas constant X ABS temperature
what is the value and units of universal gas constant
8.3J /mol K
what is the gas constant of air
287 J/kg·K
what does the air contain?
21% oxygen and 79% nitrogen
what is the molar mass of air
28.97 g/mol
what is entropy
measurement of disorder
measure of randomness or irreversibility of the system
what does the first law show us
it shows us the energy balance equation:
Q - W = change in internal energy
what does the second law show us (2)
entropy always increases or remains constant
thermal efficacy of any heat engine is always BELOW 100% (engine always produces heat)
what does the second law show us (2)
entropy always increases or remains constant
thermal efficacy of any heat engine is always BELOW 100% (engine always produces heat)
what does the third law show us
entropy is zero at zero temperature
what does irreversibility mean, from the point of view of the behaviour of the system
entropy increases in irreversible processes
how many processes does a cycle have
each cycle has 2 process as a minimum, mostly 4 but at least 2
what thermodynamics processes are there (4)
adiabatic - no heat exchange
isobaric - pressure
isochoric - volume
isothermal - temperature
