Chapter 1: Intro to thermodynamics Flashcards
Where does the energy go when our body looses internal energy?
Heat transfer, doing work, stored fat, cell repair/growth (small fraction)
what is a system?
A quantity of matter or a region in space chosen for study
what are surroundings?
The mass or region outside the system (we do our measuring in the surroundings)
What are boundaries?
Real or imaginary surface that separates the system from its surroundings.
It can be fixed or movable.
what is a closed system?
Matter can not go in and out of the system, but energy and volume can.
what is an open system?
Volume stays constant, but both mass and energy can cross the boundary.
ex: blood of human heart
what is an isolated system?
No mass, heat or work may cross the boundaries. It is a closed system with no energy crossing.
what are intensive properties?
Independent of mass of system, such as temperature, pressure and density
what are extensive properties?
Values that depend on size or extent, such as total mass & total volume
what are specific properties?
Extensive properties (depend on size) per unit mass
what is a state?
Condition of a system defined by properties.
At a given state, all properties of a system have fixed values, if one value changes, the state changes
what is the state postulate?
state of a simple compressible system is completely specified by 2 independent, intensive properties
what is a simple compressible system?
if a system involves no electrical, magnetic, gravitational, motion and surface tension effects
what is a single-phase system?
temperature and pressure are independent
what is a multi-phase system?
temperature and pressure are dependant
what is thermal equilibrium?
temperature is the same throughout the entire system
what is mechanical equilibrium?
no change in pressure at any point of the system with time
what is phase equilibrium?
the system involves 2 phases and when the mass of each phase reaches an equilibrium level and stays there, hence no exchange of mass between the 2 phases
what is a process?
change from state 1 to state 2
what is a path?
series of states through which a system passes during a process
what is a cycle?
process during which the initial and final states are identical
what is the quasistatic or quasi-equilibrium process?
- process that remains infinitely close to equilibrium state at all times.
- It is sufficiently slow process that allows system to adjust itself internally so properties in one part of system do not change any faster than those other parts.
- each and every second can be considered quasi-stable.
when do work-producing devices deliver the most amount of work?
when they operate on a quasi-equilibrium process.
Ex: boiling water in microwave
what is isothermal process?
temperature constant
what is isobaric process?
pressure constant
If temperature increases slowly, cylinder will expand to keep pressure constant
what is isochoric (isometric) process?
volume constant
what is a diathermic (diabetic) system?
energy is allowed in and out in the form of heat, system is in thermal contact with surroundings
what is adiabatic system?
no heat is allowed in or out, such as an insulated system
closed system
what is endothermic process?
process that absorbs heat
what is exothermic process?
process that releases heat
what happens to an endothermic process in a diathermic container?
decreases temperature of surroundings
what happens to exothermic process in diathermic container?
increases temperature of surroundings
what is a steady process?
does not change with time
what is a uniform process?
no change with location
what is the steady-flow process?
through a control volume, the mass and energy contents remain constant (steady process) but fluid properties may change with position (but not with time).
what are examples of steady-flow processes?
turbines, pumps, boilers, condensers, heat exchangers, power plants, refrigeration systems
what is absolute pressure?
actual pressure at a given position. It is measured relative to absolute vacuum (i.e. absolute zero pressure)
what is vacuum pressure?
pressure below atmospheric pressure
what is gauge (relative) pressure?
measured relative to local atmospheric pressure
what is atmospheric/barometric pressure
air pressure in atmosphere (what you measure) at a given point
Hydrostatic pressure
pressure exerted by a fluid at equilibrium at my point in time due to force of gravity
pressure is the same at all points in horizontal place regardless of geometry (changes in vertical plane)
what is the pressure inside of cylinder equal too?
sum of all pressures applied on it
hence combination of atmospheric pressure, pressure due to weight of piston and pressure applied by spring.
what is absolute temperature?
pressure of matter is zero, absolute zero kelvin, hence particles in substance are motionless
