Latest Physical Science Reviewer 6

1. When work is done by a system, what happens to its temperature assuming that no heat is added to it?

A. Decreases

B. Increases

C. Remains the same

D. None of these

Ans: A. Decreases

-If work is done on the system, the internal energy of the system increases. If work is done by the system, the internal of the system decreases.

2. Which states that “when two systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with each other?

A. Zeroth Law of Thermodynamics

B. First Law of Thermodynamics

C. Second Law of Thermodynamics

D. Mechanical Equivalent of Heat

Ans:  A. Zeroth Law of Thermodynamics

-The Zeroth Law of thermodynamics states that if two system are at the same in thermal equilibrium with a third system, they are in thermal equilibrium with each other. The First Law of Thermodynamics states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system. The Second Law of Thermodynamics states that in a natural, thermodynamic process, there is an increase  in the sum of the entropies of the participating systems.

3. What happens in an adiabatic process?

A. No heat enters or leaves the system.

B. The pressure of the system remains constant.

C. The temperature of the system remains constant.

D. The system does no work nor work is done on it.

Ans: A. No heat enters or leaves the system.

-An adiabatic is one in which heat is gained or lost by the system. A good example of this is the rapid compression of the air in tire pump.

4. What thermodynamic process is involved in a closed car inside a hot garage?

A. Adiabatic

B. Isobaric

C. Isochoric

D. Isothermal

Ans: C. Isochoric

-Isochoric is a thermodynamic process that takes place at constant volume so that no work is done on or by the system. A good example is that of a closed car inside a hot garage. Energy is transferred by heat into a car, the system’s volume is kept nearly constant by car’s sealed windows and doors.

5. Consider the thermal energy transfer during a chemical process. When heat is transferred to the system, the process is said to be __________ and the sign of H is ___________.

A. endothermic, positive

B. endothermic, negative

C. exothermic, positive

D. exothermic, negative

Ans: A. endothermic, positive

-Enthalpy is a thermodynamic potential, designated by letter “H”, that constants of the internal energy of the system plus the product of pressure and volume of the system. The change in enthalpy is positive in endothermic reactions, and negative in heat-releasing exothermic process.

6. Which of the following statements is FALSE?

A. Entropy increases with the number of microstates of the system.

B. Any irreversible process results in an overall increase in entropy.

C. The total entropy of the universe in any spontaneous process.

D. The change in entropy in a system depends on the initial and final states of the system and the path taken from one state to the order.

Ans: D. The change in entropy in a system depends on the initial and final states of the system and the path taken from one state to the order.

-Entropy is the natural tendency of systems to become disordered. It is a function of the number of particles and the total energy available to those particles. The difference in entropy, in any process, chemical or physical, is the entropy of the final situation minus the entropy of the initial situation. For a chemical reaction, this is the difference between the products entropy, called entropy change.

7. During a refrigeration cycle, heat is rejected by the refrigerant in ___________.

A. compressor

B. condenser

C. evaporator

D. expansion valve

Ans: B. condenser

-Heat absorbed in the refrigeration cycle, including both the heat extracted in the evaporator and the energy used to drive the cycle, must be rejected to the outside environment. The heat exchanger that rejects heat from condensing refrigerant to an external medium is known as condenser.

8. Which of the following CORRECTLY describes a refrigeration system?

A. Rejects energy to a low temperature body.

B. Rejects energy to a high temperature body.

C. Removes heat from a low temperature body and delivers it to a high temperature body.

D. Removes heat from a high temperature body and delivers it to a low temperature body.

Ans: D. Removes heat from a high temperature body and delivers it to a low temperature body.

-Refrigeration is the process in which work is done to move heat from one direction to another. It is usually the removal of heat from a high temperature body and delivers it to a low temperature body since heat naturally flows from hot to cold.

9. Which of the following refrigerant has the maximum ozone depletion potential in the stratosphere?

A. Ammonia

B. Carbon dioxide

C. Fluorine

D. Sulfur dioxide

Ans: C. Fluorine

Fluorine is a major component of chlorofluorocarbon (CFC’S) which are mainly responsible for man-made chemical ozone depletion . Their atoms acts as a catalyst that can break down tens of thousands of ozone molecules before can be removed from the stratosphere.

10. Which phenomenon  is BEST explains by the particle nature of light?

A. Doppler effect

B. Interference

C. Photoelectric effect

D. Polarization

Ans: C. Photoelectric effect

-Under the right circumstance, light can be used to push electrons, freeing them from the surface of a solid. This process is called the photoelectric effect, a material that can exhibit this phenomenon is said to be photoemissive, and the ejected electrons are called photoelectrons.

11.According to the quantum theory of light, the energy of light is carried in discrete unit called _____.

A. alpha particles

B. photoelectrons

C. photons

D. protons

Ans: C. Photons

-A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation. It is the force carrier for the electromagnetic force.

12. Ruther ford observed that most of the alpha particles directed at a metallic foil appear to pass through unhindered, with only a few deflected at large angles. What did he conclude?

A. Atoms can easily absorb and re-emit alpha particles

B. Atoms consist mainly of empty space and have small, dense nuclei.

C. Alpha particles behave like waves when they interact with atom.

D. Atoms have most of their mass distributed loosely in an electron cloud.

Ans: B. Atoms consist mainly of empty space and have small, dense nuclei.

-From the result of the scattering experiment on gold foil, Rutherford concluded that since most of the alpha particles went straight through the foil, most of the space taken up by the atoms must be empty. Also since some of the positively charged alpha particles were scattered back towards the emitted, they must be repelled by a positive part of the atom.

13. When an electron change from a higher energy to a lower energy state within an atom, a quantum of energy is___________.

A. absorbed

B. emitted

C. fissioned

D. fused

Ans: B. emitted

-If an atom, ion, or molecules is at the lowest possible energy level, it and its electrons are said to be in the ground state. If it is at a higher energy level, it is said to be excited. Such a species can be excited to a higher energy level by absorbing a proton whose energy is equal to the energy difference between the levels. Conversely, an excited species can go to a lower energy level by spontaneously emitting a photon equal to the energy difference.

14. When does nuclear fission occur?

A. When we cut nuclei into two with a very small cutting device

B. When one nucleus bumps into another causing a chain reaction

C. When a nucleus divides spontaneously, with no apparent reason

D. When electrical force inside a nucleus overpower forces

Ans: D. When electrical force inside a nucleus overpower forces

-The splitting of atomic nuclei is called nuclear fission occurs when the repelling electrical forces within a nucleus overpower the attracting nuclear strong forces.

15. When does nuclear fusion release energy?

A. When uranium emits a neutron

B. When heavy ions fuse together

C. When very light nuclei fuse together

D. When uranium spits into two fragments

Ans: C. Very light nuclei fuse together

-Nuclear fusion is a nuclear reaction in which two or more atomic nuclei collide at a very high speed and join to form a new type of atomic nucleus. It generally occurs at lighter elements only.

16. Albert Einstein’s Second postulate of Special Relativity state that the speed of light_____.

A. can decrease if the speed of the observer decreases

B. can increase if the speed of the observer increases

C. randomly changes depending upon its original light source

D. is constant regardless of the speed of the observer or the light source

Ans: D. is constant regardless of the speed of the observer or the light source

-As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is dependent if the state of motion of the emitting body. That is, light in vacuum propagates with the speed c (a fixed constant, independent of direction) in at least one system of inertial coordinates (the “stationary system”), regardless of the state of motion of the light source.

17. A passenger train travels east at high speed. One passenger is located at the east side of one car, another is located at the west side of that car. In the train’s frame, these two passengers glance up the same time. In the earth’s frame ____________.

A. they glance up simultaneously

B. the passengers glance sideways

C. the passenger at the east side glances up first

D. the passenger at the west side glances up first

Ans: D.

-The relatively of simultaneity is the concept that distant simultaneity – whether two spatially separated events occur at the same time – is not absolute, but depends on the observer’s reference frame. Based on this context, rear events happen first.

18. Benie11 travels at high speed from Earth to the star Alpha Centauri which four light years away. Which one is CORRECT in Benie11’s frame?

A. The clocks on earth and on Alpha Centauri are synchronized.

B. The trip takes more time than it does in the earth’s frame

C. Benie11 travels to Alpha Centauri over a length that is shorter than four light years.

D. Alpha Centauri travels to Benie11 over a length that is shorter than four light years.

Ans: D. Alpha Centauri travels to Benie11 over a length that is shorter than four light years.

-The Law of Contraction states that the length of any object an a moving frame will appear foreshortened in the direction of motion, or contracted. The amount of contraction can be calculated from the Lorentz transformation. The length is maximum in the frame in which object is at rest.

19. One clock is placed on top of a mountain and another clock is at the bottom the mountain. Ignore the rotation of the earth. Which clock ticks more slowly?

A. They tick at the same rate.

B. The one on top of the mountain.

C. The one at the bottom of the mountain.

D. Cannot be determined.

Ans: C. The one at the bottom of the mountain.

Gravitational time dilation is a form of time dilation, an actual difference of elapsed time between two events as measured by observers situated at varying distances from a gravitating mass. The stronger the gravitational potential (the closer the clock is to the source of gravitation), the slower time passes.

20. You are in a windowless spacecraft. What do you need to do determine whether your space ship is moving at constant non-zero velocity, or is at rest, in an inertial frame of earth?

A. Make very precise time measurements.

B. Make very precise mass measurements.

C. Make very precise length and time measurements.

D. Nothing, because you cannot succeed no matter what you do.

Ans: D. Nothing, because you cannot succeed no matter what you do.

-Since the windowless spacecraft is moving at a constant velocity in an inertial reference frame and all of the law of physics are the same in any inertial frame, there is no way for you to tell if you are moving or not.

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