Class 4 Flashcards
Temperature is related to average _______ of molecules.
Kinetic energy
Is temperature an intensive property? What does that mean?
Yes. Doesn’t depend upon the amount of material
Is heat an intensive property?
No! It depends on the amount of material and is thus extrinsic.
Does a material change temperature during phase change
No
What is the Zeroth Law of Thermodynamics?
Defines temperature as a fundamental property of any substance. When two substances are in contact, heat transfers between them until they achieve the same temperature, i.e. thermal equilibrium.
What are 3 modes of heat transfer?
- Conduction
- Convection
- Radiation
What is conduction?
Heat transfer through solids in direct contact.
Ability to conduct is material-dependent.
What is convection?
Heat transfer through fluid circulation
What is radiation?
Heat transfer by emission and absorption of electromagnetic energy
What are the relative speeds of heating?
Conduction -> Convection -> Radiation
slowest fastest
What is the equation for the first law of thermodynamics?
(delta)E = Q - W
Work (W) is positive when what does the work?
The system. Work done ON the system will be negative
When is Q positive/negative in thermodynamics?
Positive Q means energy is put INTO the system.
For an ideal gas, the only internal energy is what? And how is this measured?
Only internal energy in an ideal gas is KE which directly correlates with temperature.
For a substance to change state (e.g. liquid to gas) must there by some sort of energy transfer?
Yes, and the total amount of energy between the two are conserved
What does isochoric mean?
constant volume (delta V = 0)
What does adiabatic mean?
There is no heat transfer (Q = 0)
Pressure = ?
Force/Area
If a gas exerts pressure on a piston head and moves it, is it doing work?
Yes.
Conversely, contraction of a gas and dropping of a piston head is negative work
What is the equation for the work done by an ideal gas (when in a container)
W = P(delta)V
In an isochoric process, what is the first law of thermodynamics (eqn)?
(delta)E = Q
The system CANNOT do work because the volume CANNOT change, and thus W = 0
What is the equation for an isothermal process (in terms of first law)
Q = W
Since temperature did not change, (delta)E = 0 and it drops out.
What is the first law for an adiabatic process?
(delta)E = -W
How can you determine/estimate the work done by a system using a P-V diagram?
Work = area under the curve
Work on a system = ?
(delta)KE + (delta)PE/ (delta)E
What is specific gravity?
Density of fluid/density of water
What is gauge pressure?
Difference between surface pressure and at some other point (essentially zeroed to atmosphere).
What
is true of weight and buoyant force for a floating object?
W = Fb
density object/density water = volume submerged/volume object
Assuming flow speed, v, is constant across area, A, flow = ?
f = Av
flow rate = area x flow speed
For an incompressible fluid, is flow rate constant throughout a pipe?
A1v1 = A2v2
Speed is inversely proportional to area
What is Bernoulli’s eqn?
P1 + rhogy1 + 1/2rhov1^2 = P2 + rhogy2 + 1/2rhov2^2
P1 + PE1 + KE1 = P2 + PE2 + KE2
Work = ?
Force x distance
Inside a pump, at a constant height, higher speed (v) = ________ pressure
Lower!
Kinda counterintuitive, right?
Is any fluid exposed to the atmosphere the same t all points?
Yes
