The 7 Ideas that Shook the Universe Final Exam Part 2 of 3
At what temperature must the heat sink be held at to produce a perfect engine?
0 K
At what temperature does the volume of an ideal gas go to 0?
0 K, and -273.15 degrees celsius
Which is more efficient a Carnot engine using steam or a Carnot engine using Gasoline?
A Carnot engine using gasoline is more efficient
What were the characteristics of caloric fluid?
A fluid, colorless, massless, total amount is conserved
What kinds of energy are present in the following systems? (a) a car battery, (b) a rock on a mountain top, (c) burning gas
A. Heat energy B. Potential energy C. Heat energy
It is sometimes said that absolute zero is the temperature at which everything is "frozen solid," that is, all motion ceases. As will be pointed out in the sixth idea that shook the universe, this statement is incorrect. What might be a better definition for absolute zero?
Absolute zero means that there is no motion and the volume of the gas would be zero
What do we call a thermodynamic process where heat does not flow into or out of
Adiabatic
What is meant by the "Heat Death of the Universe" and how is this related to the second law of thermodynamics?
All of our sources of heat "will" die which will cause a lack of heat being added into the universe hence a heat death. It is related to the second law because entropy will continue to increase until it reaches equilibrium and can no longer increase
What is the relationship between entropy, probability, and disorder?
As entropy increases there is more disorder and lower probability of obtaining a specific outcome. As entropy decreases the disorder decreases and the probability of obtaining a specific outcome increases
Which requires more heat? A. Increase temp. of 0.5kg of water by 10˚C B. Increase temp. of 1kg of water by 5˚C C. Neither
C. Neither
Who's engine is considered an ideal engine?
Carnot's engine
A(n) ______ in physics is when the total amount of a quantity is constant
Conservation law
Who proposed the concept of the atom in 400BC
Democritus
From a practical standpoint, what is energy?
Energy is what is used to cause a change in an object. Some examples would be when an object is moved from one place to another, or changing the forms of an object
_______ is what makes the _______ go
Energy, Mechanism
Select the 3rd and 4th Ideas that Shook the Universe
Entropy and probability, the Energy concept
Carnot's engine is a perfect engine. (True/False)
False
Energy may appear to come from nothing in an isolated system(True/false)
False
What were the supposed properties of caloric fluid?
Fluid, colorless, massless, and conserved
Explain phase changes, including latent heats, in terms of kinetic molecular theory
For a phase change to occur extra energy has to be put in. Latent heat is the amount of energy needed to change an object from one form to another temp does not increase
In which direction is the natural flow of heat?
From hot to cold
What direction does heat flow?
From hot to cold
What were the characteristics of phlogiston?
Had mass could be absorbed or released during burning, was a fluid
What are the two important results of Joule's paddle wheel experiment?
He found that the mechanical work done on a system was equal to the heat produced. He discovered the value of J (Joule)
Who is Maxwell's Demon and what does he do?
He is an imaginary demon trapped in an isolated box and his job is to separate the fast gases from the slow gases decreasing entropy
Why did Count Rumford question the validity of caloric theory?
He questioned it because he believed that the amount of caloric fluid released should have melted the cannons but it didn't
Define heat capacity and specific heat
Heat capacity is the amount of heat needed to raise the given mass of material by 1 degree Celsius. Amount of temp needed to raise 1 gram of the material 1 degree Celsius
What is heat in terms of kinetic molecular theory?
Heat is molecular motion
How is temperature distinguished from heat?
Heat is the energy that flows to and from an object due to a temperature difference, it is the process that happens to objects. Temperature is a parameter of the object, and a property of an object
Joule's paddle wheel showed the equivalence of which 2 forms of energy?
Heat, Mechanical Energy
Give an example of a nearly elastic collision, besides billiard balls. Give an example of a highly inelastic collision
Hitting a baseball would be an example of an elastic collision. Running into a brick wall would be a highly inelastic collision
If you were told that some company had invented a new kind of electric power plant that was, in theory, three times more efficient than the best present-day power plants, would you invest money in that company?
I would want to actually see what they're doing first; I would invest in them as long as it is more efficient than previous ones
Which law describes the macroscopic properties of gases?
Ideal gas law
What is the Zeroth Law of Thermodynamics?
If 2 thermodynamic systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other
What do we call a line on a P-V diagram that corresponds to an unchanging temperature?
Isothermal
Define the terms isothermal and adiabatic
Isothermal means that there is a constant temperature. Adiabatic means that there is no heat flow
Why is the Carnot engine important?
It is important because it is the engine with the maximum "attainable" efficiency
Why is entropy referred to as "time's arrow"?
It is referred to as "time's arrow" because entropy in an isolated system always increases and never decreases. So as time goes on entropy will continue to increase
Why should the equilibrium distribution be the most probable distribution?
It is the most probable distribution because over time an equilibrium will be reached
Why is potential energy referred to as "potential" energy?
It is the stored-up energy in an object when the object is still at rest. It has the possibility(potential) to use that stored energy. An object having the ability to acquire kinetic energy
If you double your speed, by how much does your kinetic energy increase?
It quadrupoles
How does recognizing heat as a form of energy "save" the conservation of energy principle for a real pendulum?
It shows where the energy that seemed to disappear or be destroyed went. Heat being recognized shows that energy is conserved
Why is it understandable that scientists first believed heat to be a fluid?
It was believed to be like the soul of matter and that it would flow into objects and cause them to heat up or would be released when an object was heated up. It is understandable because they believed that it was something that they could see
Which theory is used to describe the microscopic nature of gases?
Kinetic Molecular Theory
What is conserved in an elastic collision?
Kinetic energy and momentum
List 5 basic forms of energy
Kinetic, Potential, Heat, Radiant, Mass
The 1st law of thermodynamics is a restatement of which law of thermodynamics?
Law of Conservation of Energy
What is conserved in an inelastic collision?
Momentum
What is conserved in an elastic collision?
Momentum and kinetic energy
What is the difference between momentum and kinetic energy?
Momentum is the product of mass times velocity. Kinetic energy is the energy of motion it gets very big very fast because of the velocity squared term. Kinetic energy is half the mass times velocity squared while momentum is mass times velocity
Does Maxwell's Demon violate the 2nd law of thermodynamics? (Yes/No)
No
Is it possible to convert all of the heat energy that flows through an engine into work? (Yes/No)
No
How much heat can be transferred into a system during an adiabatic process?
No heat can be transferred since there is no heat flow
People sometimes talk about putting "cold" into a system. Can this be explained by the caloric theory of heat, or any other theory of heat? Justify your response
No, all of the heat theories have to do with adding temperature to things and they point out that heat cannot be turned back into other forms of energy. Cold can be added into a Non-isolated system
When hot food is placed in a working refrigerator its entropy decreases. Is this a violation of the Second Law of Thermodynamics? Justify your response
No, it is not a violation because the refrigerator has to be plugged in or get power from something to allow it to cool off, so it is not an isolated system
Do all systems have the same equation of state?
No, the equation depends on all the parameters that are in the system being observed
What is an "isolated" system?
Nothing from the inside is lost and nothing from the outside is added. There are no outside influences. No where else for stuff to go
What is meant by a conservative system? Give an example of a conservative system
Nothing is gained or lost in the system, things only change properties in the system but are always there. The entire Universe
What is meant by the "energy distribution for the molecules of a system"?
Over time the distribution of energy in a system moves towards a state of equilibrium
What is meant by a parameter of a System?
Parameters are measurable or calculable properties in a system
Why is heat a degraded form of energy?
The energy put into the heat sink is considered degraded because it is no longer available for transformation, no longer useful as input heat
Which of the following is an isolated system?
The entire Universe
What is the First Law of Thermodynamics? How does it apply to systems that are not Isolated?
The first law states that the total amount of energy is conserved in an isolated system. For a system that isn't isolated the change in the Internal Energy of that System equals the Heat added to the System minus the Work done by the System
What is meant by an equation of state? How is an equation of state used to determine the temperature of a system?
The mathematical relationship among all the parameters of the system. It tells us how the change in one parameter affects the other parameters which you can use to determine the temperature of a system
Heat is allowed to flow from a high-temperature reservoir to a low temperature reservoir. How can the resulting entropy increase be minimized?
The resulting entropy increase can be minimized by putting both temperature reservoirs into a very cold room and close the room off
What is the difference between heat and temperature?
The temp. of an object is the average kinetic energy per molecule. The heat content of an object is the total kinetic energy of all the molecules
Define work in the 'physics' sense of the word
The work done is equal to the change in energy
State the Law of Conservation of Energy in your own words
There is a fixed amount of total energy in an isolated system
We say 2 objects are in _________ when heat no longer flows between them
Thermal equilibrium
List all of the forms of the Second Law of Thermodynamics discussed in class.
Version #1: "In an isolated system, there is no way to reverse the flow of Heat - it flows from higher temperature to lower temperature." Version #2: "It is impossible to have a Heat Engine work in a cycle that will result in complete (100%) conversion of Heat into Work." Version #3: "The entropy of an isolated system can never decrease; it can only increase or stay the same."
State the Third Law of Thermodynamics
Version #1: "It is not possible to reach the absolute zero of temperature in a finite number of steps."
What is a conservation law?
Very important laws, they provide a link between theory and physical reality. A conserved quantity is when nothing is gained or lost of something, it has a set amount. Conservation laws describe these things
Who developed the concept of energy conservation by observing the color of blood
Von Mayer
What is the connection between entropy change and probability?
When entropy increases the order in a system decreases which lowers the probability of obtaining a specific outcome. When entropy decreases the probability of obtaining a specific outcome increases
What do we call it when a force acts on an object over a distance?
Work
What does the area enclosed in a PV diagram represent?
Work
What were the supposed properties of phlogiston?
fluid
What is conserved in an inelastic collision?
momentum
