Reading Quiz

Question 1:

Answer:

1. one degree corresponds to Kinetic energy and one degree to Potential energy.
2. Each mode of vibrationhal energy counts as two degrees of freedom because one is for kinetic energy and the other for potential
3. One degree is for the vibrational kinetic energy, the other is for the potential energy.
4. One of the vibrational kinetic energy and one for the potential energy.
5. I'm not sure.
6. One degree of freedom is for the vibrational kinetic energy and the other is for the potential energy. Each mode of vibration counts as two degrees of freedom because the vibration of the atoms has both kinetic and potential energy associated with it.
7. Because there is one for the vibrational kinetic energy and one for the vibrational potential energy. This comes about from the simple harmonic oscillator, whose average kinetic and potential energies are equal.
8. Because the atoms vibrate in two dimensions.

Question 2:

Answer:

1. most of the time the vibrational degrees of freedom do not contribute to the molecule's energy at room temperature. Collisions that occur at room temperature rarely cause a molecule to vibrate, just rotate.
2. For molecules at room temperature, vibrational degrees of freedom do not contribute to the thermal energy. Collisions with molecules make an air molecule rotate but not vibrate.
3. At room temperature, vibrational degrees of freedom do not contribute to a molecule's thermal energy.
4. They are effectively "frozen out" b.c they are not significant enough to contribute to a molecules thermal energy.
5. There are 6. Two for each perpendicular direction
6. At room temperature the vibrational degrees of freedom do not contribute to the molecule's thermal energy.
7. At room temperature, many vibrational degrees of freedom do not contribute to a molecule's thermal energy. The modes are said to be "frozen out" at room temperature, but at higher temperatures, they do start to contribute. The reasoning lies in quantum mechanics.
8. The energy imput into a gas at room temperature is insufficient to induce vibration , so there are none.

Question 3:

Answer:

1. They both correspond to energy being taken out of a system, or put into a system.
2. Heat and work both transfer energy in or out of a system
3. Both heat and work refer to energy in transit.
4. They are two mechanisms for which energy can be put into or taken out of a system.
5. They can put energy into a system
6. Both heat and work refer to energy in transit. This means that heat and work deal with energy changes as in how much energy enters a system or how much energy was done on a system.
7. They both refer to energy in transit. We cannot talk of how much heat or work is in a system, only how much entered or was done on the system.
8. They both describe the movement of energy.

Question 4:

Answer:

1. 'change in heat' or 'change in work' are meaningless because they are ways in which energy is added to a system, they are not descriptions of the system themselves so they cannot be treated in the same way as a characteristic of the system, such as Temperature, would.
2. ? I thought that you can only discuss how much heat enters or leaves a system or how much work was done on a system but it is meaningless to discuss how much heat or work is in a system. Do I have this backward? the amount entered or leaving gives the change in energy
3. It would not make sense to say there is heat or work "in" a system. Heat enters a system, and work is done on a system.
4. heat and work describe energy in transit, and can only be discussed as heat entered, exchanged or work done. you can't for example, talk about how much work is in a system.
5. Not sure
6. Because there is no such thing as a total amount of heat or work inside of a system. A system does not have a total quantity of heat or work. Both heat and work say how the energy has changed in a system. So you cannot say what the change in heat is since the definition of heat deals with a change itself.
7. Because these are not elements of the system. They are external to the system, and thus cannot have a changing rate within the observed system.
8. Because these quantities are often considered as infinitesimal.

Question 5:

Answer:

1. The energy change of a system is equal to the work done on the system plus the heat added to that system. It is a statement of conservation of energy.
2. The change in energy is equal to the heat added plus the work done. It is basically conservation of energy.
3. DeltaU=Q+W : this equation means that the total change in energy DeltaU, is equal to the amounts of energy that enter a system as heat or work.
4. delta U = Q + W, this is a statement of conservation of energy... the total change in energy of a system is the sum of heat added to it and the work down on it.
5. Delta U = Q + W The change in energy equals the heat added plus the work done.
6. deltaU = Q + W. The change in the total energy in a system = The amount of energy that enters a system though heat + the amount of energy that eneters a system through work. Both the values for Q and W can be negative since energy can enter or leave as heat and work can be done on the system and by the system. Essentially the total energy change is found by adding the heat and work since these two quantities describe how energy enters and leaves a system.
7. (change in)U=Q+W. This is a statement of the law of conservation of energy, which says that U, the total energy inside the system, is the addition of Q, the amount of heat that enters the system, and W, the amount of work done on the system, over time.
8. energy equals heat plus work.