Chapter 4: Thermodynamics Flashcards
The zeroth law of thermodynamics states:
objects are in thermal equilibrium (there is no net transfer of heat) when they are at the same temperature; if a=b and b=c, then a=c
Temperature is:
a physical property of matter related to the average kinetic energy of particles.
Differences in temperature determine:
the direction of heat flow (heat flows from hot to cold)
Heat (energy) spontaneously flows from:
hot temperatures to cold temperatures
If no net heat flows between two objects in thermal contact, we can say that:
their temperatures are equal and they are in thermal equilibrium
Absolute zero
the temperature at which all random atomic motion stops because there is zero thermal energy (0 degrees Kelvin is absolute zero)
Kelvin to Celsius Equation
Tc = Tk - 273
Celsius to Fahrenheit Equation
Tf = (9/5)Tc + 32
Thermal Expansion is:
The change in an object’s size with a change in temperature. In general, objects expand as the temperature increases.
The change in length of a solid object due to temperature can be found with what equation?
ΔL = αLΔT
(where ΔL is the change in length; L is the original length; ΔT is the change in temperature; and α is the coefficient of linear expansion of the object)
The change in volume of a liquid or solid object due to temperature can be found with what equation?
ΔV = **βVΔT**
(where ΔV is the change in volume; β is 3α; V is the original volume; and ΔT is the change in temperature)
First Law of Thermodynamics states:
the change in the total internal energy of a system is equal to the amount of energy transferred in the form of heat to the system, minus the amount of energy transferred from the system in the form of work.
The internal energy of a system can be increased by:
adding heat, doing work on the system, or some combination of both processes.
The change in internal energy (ΔU) of a system is calculated from what equation?
ΔU = Q - W
(where ΔU is the change in internal energy of the system; Q is the energy transferred through heat to the system; and W is the work done by the system).
NOTE: work done on the system and heat flow out of the system are always negative; opposite is positive.
Work done by a system is always:
positive
Work done on a system is always:
negative
Heat flow into a system is always:
positive
Heat flow out of a system is always:
negative
A system is:
the object we are paying attention to
An environment is:
everything surrounding the system that is not a part of the system
Energy be can be neither:
created or destroyed. Thus, the energy of a closed system will always be constant.
Work is the process by which:
energy is transferred as the result of force being applied through some distance (W=Fdcosθ)
The only two process by which energy can be transferred from one object to another are:
work and heat
Heat is the process of:
energy transfer between two objects at different temperatures and one that will continue until the two objects come into thermal equilibrium (i.e. reach the same temperature)
In regards to heat, the second law of thermodynamics states:
objects in thermal contact and not in thermal equilibrium will exchange heat energy such that the object with the higher temperature will give off heat energy to the object with a lower temperature until both objects have the same temperature (i.e. reach thermal equilibrium)
The four different units of heat:
Joules (J); calories (cal); British Thermal Unit (Btu); Calorie (Cal)
The conversion factors between the units of heat:
1 Cal = 103cal = 3.97 Btu = 4,184 J
The three means by which heat can transfer energy:
conduction, convection, and radiation
Conduction is:
the direct transfer of energy from molecule to molecule through molecular collisions (there must be physical contact between two objects for conduction to occur)