Thermo Exam 1
How many kJ is 5 Btu of energy using conversion ratio to make calculation?
1 btu = 1.0551 kJ 5(1.0551) = 5.276 kJ
match the following 1) hf 2) hfg 3) hg
1) enthalpy of saturated liquid 2) enthalpy of vaporization 3) enthalpy of saturated vapor
What are the units for each of the following? 1) heat transfer 2) heat transfer per unit mass 3) rate of heat transfer
1) kJ 2) kJ/kg 3) kW
Statistical Thermodynamics
A microscopic approach, based on the average behavior of large groups of individual particles.
work is the energy transfer associated with ___________ acting through a distance
force
a tank contains 5 kg of a saturated liquid-vapor mixture with 2 kg in the vapor phase. Determine the quality of the mixture
0.4
Following the formal sign convention, please match the heat and work interactions with their appropriate signs 1) work done by system 2) work done on system 3) heat transfer into system 4) heat transfer out of system
1) positive work 2) negative work 3) positive heat 4) negative heat
how many seconds are equal to 1 nanosecond?
10^-9
a potato is baked in the oven. disregarding moisture loss, and assuming potato is well insulated, if 2kJ of heat is transferred into potato, what is the energy change of the potato
2 kJ
10 kJ of heat is transferred to a control volume and 7 kJ of work is done on the control volume. Some mass also enters or leaves the system. If the energy change of the system is zero, the energy of the mass entering or leaving the system is...
3 kJ out
The density of water is assumed to be 1000kg/m^3. If the gage pressure of a water column 10m high is 10kPA, then the gage pressure of a water column 30m high should be ____________
30 kPa
heat is added to a system to raise its temperature 10 degrees C in 20 minutes. If the rate of heat transfer were cut in half, how long would the process have to run in order to transfer an equivalent amount of heat
40 min
The rankine scale of temperature equals the Fahrenheit scale plus __________
459.67
If the gas pressure inside a sealed tank is 689 kPa absolute, what is this pressure in lbs force per square inch
6.89 kPa = 1 psi = 100 psia
select the correct statements regarding the definition of a cycle.
A cycle has identical initial and final states a cycle may include multiple processes a cycle always returns to its initial state at the end of a process
Classical Thermodynamics
A macroscopic approach to the study of thermodynamics that does not require a knowledge of the behavior of individual particles.
which of the following statements are true regarding the similarities between heat and work?
both are associated with a process both are path functions both can cross the boundary of a system
knowing the compressibility factor of the following gases, which gas's behavior below deviates the most from ideal gas behavior?
gas E, z=0.2
An adiabatic process is one in which there is no ____________ _____________
heat transfer
In engineering, all equations must be dimensionally __________________ , which implies that every term must have the same unit.
homogeneous
consider the following example. a liquid is heated at a constant pressure until it exists as a gas. At which of the following states would it be considered a saturated vapor?
all of the mass is in vapor phase, and substance is at boiling point. if any heat were lost, substance would start to condense.
consider the following example. a liquid is heated at constant pressure until it exists as a gas. at which of the following states would it be considered a compressed liquid?
all of the mass is liquid, and it is not about to vaporize
if the system reaches a given state, which of the following is true?
all of the properties have fixed values
select the statements that best express the first law of thermodynamics
energy cannot be created or destroyed energy is conserved the change in total energy of a conserved system during an adiabatic process must be equal to the net work input
which one of the following selections is a solid?
ice
saturated vapor is vapor in a state that is not about to condense.
false
Intensive properties are those whose values depend on the size or extent of the system
False
determine the barometric reading at a location where the atmospheric pressure is 110kPa and the gravitational acceleration is g=9.085 m/s^2. Assume the temp of mercury is 10 degrees C. At which its density is 13570 kg/m^3
P=pgh 110=13750(9.085)(h) 0.8267m
Which of the following units are units of pressure?
Pa mmHg psi
We can approximate 1 atm by 100kPa. If a tire's gage pressure is 200 kPa, what is its corresponding absolute pressure
Pgage=Pabs-Patm Pabs=Pgage+Patm 200+100=300kPa
a manometer is used to measure ______________
differential pressure
It is assumed that the density of water is 1000 kg/m^3. If the specific gravity of mercury is 13.6, what is the density of mercury?
SG=density/density of water 13.6=density/1000 density = 13,600 kg/m^3
heat is a form of energy transfer by virtue of a _____________ difference
temperature
first law of thermodynamics
The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.
for an ideal gas under constant pressure, if the volume is doubled, the temp of the gas will _____________
double
System
a quantity of matter or a region of space chosen for a study
which of the following are applications of thermodynamics?
a solar hot water system refrigerator car engine
Select all that can be classified as purified substances
a tank containing liquid nitrogen a glass of ice water a liquid-vapor mixture of ammonia
the conservation of energy principle is also known as an expression of the
first law of thermodynamics
For a compressible system, the change in total energy of a system during a process is affected by
changes in potential, kinetic, and internal energy
a substance initially exists as a compressed liquid at a pressure below the critical point. It is heated at constant pressure until it becomes a superheated vapor. Put the following phases in the order they would occur in the process. Begin with compressed liquid at the top.
compressed liquid saturated liquid saturated liquid-vapor mixture saturated vapor superheated vapor
which of the following devices is not suitable for using a control volume (open system) in the thermodynamic analysis of the system?
compressed nitrogen in a sealed tank
__________________ is the transfer of energy from the more energetic particles of a substance to the adjacent less energetic ones as a result of interaction between the particles.
conduction
On a t-v diagram, the point where the saturated vapor line and saturated liquid line meet is called the ___________ point
critical
on a p-t diagram, the vaporization line ends at the ____________ point because no distinction can be made between liquid and vapor phases above it
critical
the electrical power equals to a square of the _______________ multiplying the resistance
current
a system is said to have undergone a _____________ if it returns to its initial state at the end of the process
cycle
When mass enters a system, energy in the system
increases
The sum of all the microscopic forms of energy is called the ______________________ energy
internal
if the gas in a piston-cyclinder device undergoes a quasi-equilibrium compression, the pressure in a system...
is approximately uniform throughout the system at each moment in time.
which of the following statements describes a saturated vapor?
it is still 100% vapor it is about to condense any heat removed will cause the vapor to condense it refers to a point on the T-v diagram at a specific temp
what is the specific enthalpy?
kJ/kg
which energy forms of the following are macroscopic?
kinetic energy potential energy
amount of energy absorbed or released during a phase change process is called the _______________ heat
latent
the amount of energy released during a phase change process is called the _______________ heat
latent
for linear elastic springs, the displacement of the spring is ______________ to the force applied
linearly proportional
the term uniform flow implies flow with no change with a specific ________________
location
for a given pressure, a compressed liquid has ___________ temp than a saturated liquid
lower
which of the following properties are extensive?
mass weight volume
select the primary or fundamental dimensions of a system
mass (kg) length (m) time (s) temperature (K)
Besides length and time, which of the following is a primary dimension of the SI metric system?
mass in kg
the density of a substance is most likely dependent on
temperature and pressure
on a t-v diagram, the region under the dome between the saturated liquid and saturated vapor lines, the substance exists as a _____________________
mixture of liquid and vapor
which of the following are true regarding gases?
molecules move about at random the molecules are far apart from each other, and a molecular order is non-existent it must release a large amount of energy before it can condense when compared to a solid
a system is a simple compressible system in the absence of ____________ and surface tension effects
motion gravitational magnetic electrical
which of the following energy forms are microscopic?
nuclear energy latent energy sensible energy
efficiency can be described in terms of the desired ___________ divided by the required ________________.
output, input
the series of states through which a system passes during a process is called the _____________ of the process
path
the p-t diagram is often called the ____________ diagram since all three phases are separated from each other by three lines
phase
the electrical power is defined by the product of the ___________ difference and the __________________
potential, current
for the following properties select one that is not an extensive property momentum volume pressure mass kinetic energy
pressure
the saturation temperature of a substance is affected by which of the following properties?
pressure
from the following properties, select those that characterize a system, also known as the system's properties
pressure thermal conductivity viscosity
which of the following is true for pressure?
pressure is defined as a normal force exerted by a fluid per unit are pressure in fluid systems is similar to normal stress for a solid
any equation that relates the ___________________, _______________________, and specific volume of a substance is called an equation of the state
pressure, temperature
second law of thermodynamics
the entropy of the universe is always increasing or constant
the derivation of a gas from ideal-gas behavior is ___________________ in the vicinity of the critical point
the greatest
the second law of thermodynamics asserts that energy has _______________ as well as _____________
quality, quantity
on a t-v diagram, the saturated liquid states can be connected by a line called the ____________ liquid line, and the saturated vapor states can be connected by the ______________ vapor line
saturated, saturated
which one of the following are examples of mechanical work?
shaft work spring work
take a look at the systems below. Select the ones where conservation of energy plays a critical role
solar battery charger a human body that undergoes metabolism an automobile engine a turbine in a hydro powerplant
a property that combines internal energy and the product of pressure and specific volume, represented by the symbol h, is known as ____________ _____________
specific enthalpy
Conservation of energy principle
states that during an interaction, energy can change from one form to another but the total amount of energy remains constant, energy cannot be created or destroyed
The mass or region outside of the system is called the _________________________
surroundings
which of the following is a primary dimension of the english system?
temp (R) mass (lbm) length (ft)
an isothermal process is a process during which _____________ remains constant
temperature
which of the following best defines a liquid?
the molecular spacing is similar to that of a solid, but the molecules are not fixed with respect to each other
select all of the following that are true about the critical point
the saturated vapor state is identical to the saturated liquid state at pressures above the critical pressure, there is no distinct phase change process
consider the following example. a liquid is heated at a constant pressure until it exists as a gas. At which of the following states would it be considered a saturated liquid-vapor?
the substance is at boiling point and both liquid and vapor phases are present
select all of the ways in which a process can be adiabatic
the system is well insulated the system is at the same temp as the surroundings
two bodies are brought into contact in an isolated enclosure until they both reach the same temperature. The two bodies have reached a state of __________________________
thermal equilibrium
which of the following is not a pressure measurement device?
thermocouple
the power transmitted by a shaft is proportional to the __________ applied and the __________________ speed
torque, rotational
the point at which solid, liquid, and vapor coexist in equilibrium on the p-t diagram is called the _______________ point
triple
Gage pressure can be positive or negative
true
Specification of two independent intensive properties in a simple compressible system is sufficient to define a state
true
extensive properties per __________ are called specific properties
unit mass
which of the following systems/devices demonstrates application of thermodynamic principles
water heater pressure cooker car radiator humidifier
power is defined by ___________ done per unit __________
work, time
System A is a thermometer. Systems A, B, and C are not in contact with one another, but are all the same temperature. It can be stated that system B and C are in thermal equilibrium because of the ___________________ law of thermodynamics
zeroth