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Level 147

Laws of Thermodynamics


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first law of thermodynamics
states that energy can be converted from one for to another but cannot be created or destroyed
Big Bang Theory
tells us that the universe began as an infinite amount of energy exploded and began to spread into the universe as we know it today
Spontaneous Process
a process that occurs without the need for additional energy
Law of Energy Conservation
first law of thermodynamics, energy cannot be created nor destroyed
Law of Entropy
second law of thermodynamics, the entropy of an isolated system never decreases
Isolated System
A system that has are no energy transfers between that system and its surroundings.
Thermodynamic Equilibrium
when there are no net flows of matter, energy, no phase changes, no driving forces within a system
Entropy
a measure of the degree of randomness of the particles, such as molecules, in a system.
Second Law of Thermodynamics
States that the entropy of an isolated system never decreases, because isolated systems spontaneously evolve towards thermodynamic equilibrium -- the state of maximum entropy.
Third Law of Thermodynamics
states that the entropy of a system approaches a constant value as the temperature approaches zero
kinetic energy
a running dog
Potential Energy
(mass) x (g) x (height)
inertia
_______ is the property of an object that leads it to resist any change in motion
weight
A force that comes from gravity pulling down on any object with mass
Free Falling
no other forces except gravity are acting on the object
Thermodynamics (definition)
The study of energy and energy transformations.
0th Law of thermodynamics (nickname)
If A and B are the same temperature and B and C are the same temperature then A and C are the same temperature.
1st Law of Thermodynamics
Conservation of energy. dU = 0 for isolated system.
An example of the First law of thermodynamics
Heat flows into water from the burner, increasing the water's internal energy.
Human Metabolism
An example of the First law of thermodynamics
specifics in the first law
because W in the equation represents work done BY the system, if work is done ON the system, W is negative (and U will increase) ... similarly, since Q is positive for heat ADDE…
2nd Law of Thermodynamics
Entropy in the universe increases.
3rd law of thermodynamics (def)
entropy for a perfect krystal at 0 K is Zero. Molecular vibrations from KE at temperature above zero Kelvin lead to disorder and an imperfect crystal
It can be converted, though heat is always generated.
Energy can neither be created nor destroyed. However, according to the first and second laws of thermodynamics, what can happen to it, and what is always generated?
Surroundings
Everything outside the energy system that you are talking about
Open System
A system in which both energy and matter can enter or exit
Closed System
A system containing a fixed amount of matter; it can still exchange energy with the surroundings.
Chemical reaction (definition)
Process during which chemical bonds of a molecule are broken or new ones are formed.
heat
What is q in the specific heat formula?
work
a force acting upon an object to cause a displacement. (key words: force, displacement, and cause)
isothermal process
a process where the temperature does not change (so ∆U = 0) ~ if carried out on the ideal gas, PV = nRT becomes PV = constant
PV diagram for an ideal gas undergoing isothermal processes at two different temperatures
both temperatures have the same curve, one is just above the other (T = constant, ∆U = 0, and Q = W) ~ when comparing PV of one temperature to another, their products must be EQUAL
for isothermal process to occur, we assume...
there is a heat reservoir (a body whose mass is so large that its temperature does not change significantly when heat is changed with out system), and the process of compression or expansion is …
adiabatic process
a process in which no heat is allowed to flow into or out of the system (Q = 0 and ∆U = -W) ~ this can occur if the system is completely insulated o…
Isobaric process
pressure is constant
isochoric (isovolumetric) process
velocity remains constant, so the process is represented by a straight vertical line on the PV diagram (W = 0) ~ if it's falling, temperature decreases (and vice-versa)
Heat Engine
a machine that transform heat into mechanical power: steam heating.
heat engine equation
Q(H) = W + Q(L)
operating temperatures
T(H) and T(L) of the engine
Efficiency
_______ compares the amount of output work to the input work.
Kelvin-Planck statement of the second law of thermodynamics
no device is possible whose sole effect is to transform a given amount of heat completely into work (i.e. no engine can be 100% efficient)
Adiabatic
different temperature
Endothermic
This is when energy flows INTO the SYSTEM from the surroundings.
Exothermic
This is when energy is flowing OUT of the SYSTEM.
Heat Pump
A machine that uses work to drive heat flow
Isobaric
constant pressure
Isolated Systems
A system in which neither energy nor matter can enter or exit.
Law of Conservation of Matter
A law stating that matter cannot be created or destroyed in chemical reactions; It can only be rearranged.
Potential Energy Diagram
A diagram that displays the potential energy of a system on the y-axis and the reaction progress on the x-axis.
Example of doing work to increase heat by increasing its kinetic energy.
Air in diesel engine has an initial temperature of 27 C. When this air is compressed by the piston until it occupies one-twentieth of the original volume. This raises the temperature to 721 C
Internal Energy
Energy stored in a system as kinetic energy and potential energy.
Heat & work
_______&_______are energy in transition
Movement
Dynamics=
Heat movement
Thermal dynamics
thermal energy
a hot coffee mug
u
average speed of a molecule
Q
energy transfer (Joules)
Joules (J)
Heat units