3. Themodynamics (Physics) Flashcards
What is the zeroth law of thermodynamics?
The zeroth law of thermodynamics states that objects are in thermal equilibrium when they are at the same temperature.
What’s the relationship between temperature, heat, and kinetic energy?
Temperature is a qualitative measure of how hot or cold an object is; quantitatively, it is related to the average kinetic energy of the particles that make up a substance.
Temperature: measure of the average kinetic energy of the particles
Heat: transfer of thermal energy from a hotter object with higher temperature to a object with lower temperature.
(Equation) What is the equation for length change based on a temperature of a solid?
∆L= αL∆T
∆L= change in length
α= coefficient of linear expansion (given)
L= original length
∆T= change in temperature
(Equation) What is the equation for volume change based on a temperature of a liquid?
∆V= αV∆T
∆L= change in length
α= coefficient of linear expansion (given)
L= original length
∆T= change in temperature
What is the maximum distance that two objects can be from one another and still adhere to the zeroth law of thermodynamics?
Technically, none
Book: While there may be a distance at which thermal equilibrium is impractical, there is no theoretical maximum distance. As long as two objects are in thermal contact and at the same temperature, they are in thermal equilibrium.
Zeroth Law: The zeroth law of thermodynamics states that objects are in thermal equilibrium when they are at the same temperature.
How do the initial length of an object and the amount it expands for a given temperature change relate to one and other?
Book: Expansion is a result of an increase in dimension at all points along an object. If an object is initially longer, it will experience a greater expansion. This is also represented in the formula for thermal expansion because there is a direct relationship between length change and the initial length of an object.
True or False: the kelvin scale is the most accurate measurement for temperature because it is based on absolute zero.
False: they are all accurate, they just have different units they are measuring.
Which of the following thermodynamic systems transfer matters? Transfer energy?
Open System:
Closed System:
Isolated System:
Matter: open system
Transfer Energy: Closed and open systems
Isolated systems: no transfer of ANY energy or matter
(Equation) What is the first law of thermodynamics?
∆U= Q-W
∆U= change in internal energy= positive: increase temperature= neg: decrease temp
Q= heat= +: heat flows into system, - : heat flows out of system
W= work= +: work is done by the system (expansion), -: work is done on the system (compression).
You can think of T as temperature, Q as heat, and W as pressure.
The first law of thermodynamics is a statement of conservation of energy: the total energy in the universe can never decrease or increase.
(Equation) What is the equation for temperature change without phase change?
q=mc∆T
q= heat
m= mass
c= specific heat value
T= change in temperature (generally Kelvin)
True or false: to transfer heat, objects need to touch each other.
False. This can occur by convection or radiation.
Conduction is when they are both directly touching each other.
What type of phase (gas, liquid, solid) is the poorest conductor of heat, and why?
Gases are the poorest conductors of heat because there is so much space between the molecules.
(Equation): What is the equation for an isothermal process, and what is an example?
Q = W because (ΔU = 0)
Isothermal means no temperature change.
ΔU= temperature
Q= heat
W= work (or pressure)
Temperature= heat - pressure
An example would be a boiling pot of water. It stays the same temperature.
(Equation): What is the equation for an adiabatic process, and what is an example?
Adiabatic= no heat exchange
ΔU = −W because (Q = 0)
W=PΔV
Adiabatic= no heat exchange (A (absence diabtic= diablo- no heat)
ΔU= temperature
Q= heat
W= work (or pressure)
Example: Pot without a heat source, just being pressurized.
(Equation): What is the equation for an isobaric process, and what is an example?
Pressure is held constant.
Multiple forms.
A pot that is open to the air that is being heated.
It should be noted, something could be isobaric and isothermic.
(Equation): What is the equation for an isochoric process, and what is an example?
Isochoric= same volume, so there is no work
ΔU = Q because (W = 0)
An example is a pressure cooker with a lid. The volume is going to be the same.
Draw a representative graph of the temperature of a solid object as it is heated and goes through two phase changes to become a gas.
(Equation) What is the equation for entropy?
ΔS= entropy
Key concept: The universe is a closed, expanding system, so you know that the entropy of the universe is always increasing. The more space that appears with the expansion of the universe, the more space there is for the entire universe’s energy to be distributed and the total entropy of the universe to increase irreversibly.
