Chapter 13 The Atomic Nucleus and Radioactivity
13.1 Radioactivity
1) Radioactivity is a tendency for an element or a material to ________.
A) emit radiation
B) emit light
C) emit electrons
D) glow in the dark
E) radiate heat
Answer: A
The image below shows a beam of radiation passing between two electrically charged plates.
2) Which of the beams is due to alpha particles?
A) a
B) b
C) c
D) all of the above
E) none of the above
Answer: C
3) Which of the beams is due to an energetic light wave?
A) a
B) b
C) c
D) all of the above
E) none of the above
Answer: B
4) Which of the beams is actually composed of particles?
A) a
B) b
C) c
D) a and c
E) all of the above
Answer: D
5) Which of the beams is due to a high energy electron?
A) a
B) b
C) c
D) all of the above
E) none of the above
Answer: A
6) Which of the beams is due to a positively charged helium nucleus?
A) a
B) b
C) c
D) all of the above
E) none of the above
Answer: C
7) Which of the following provides the minimum amount of protection you need to block the
following form of radiation?
alpha
A) lead suit
B) suntan lotion
C) thick leather
D) T-shirt
E) none of the above
Answer: B
8) Which of the following provides the minimum amount of protection you need to block the
following form of radiation?
beta
A) lead suit
B) suntan lotion
C) thick leather
D) T-shirt
E) none of the above
Answer: C
9) Which of the following provides the minimum amount of protection you need to block the
following form of radiation?
gamma
A) lead suit
B) suntan lotion
C) thick leather
D) T-shirt
E) none of the above
Answer: A
10) You are given three radioactive samples (α, β, and γ) and can only dispose of one. The other
two you must keep, one in your hand, the other in your pocket. How would you minimize your
exposure risk?
A) keep α in hand, keep β in pocket, and dispose of γ
B) dispose of α, keep β in hand, and keep γ in pocket
C) dispose of α, keep β in pocket and keep γ in hand
D) keep α in pocket, dispose of β, and keep γ in hand
E) keep α in hand, dispose of β, and keep γ in pocket
Answer: A
11) Is it at all possible for a hydrogen nucleus to emit an alpha particle?
A) yes, because alpha particles are the simplest form of radiation
B) no, because it would require the nuclear fission of hydrogen, which is impossible
C) yes, but it does not occur very frequently
D) no, because it does not contain enough nucleons
Answer: D
12) Alpha and beta rays are deflected in opposite directions in a magnetic field because
A) they have opposite charges.
B) they spin in opposite directions.
C) alpha particles contain nucleons and beta particles do not.
D) all of the above
Answer: A
13) The alpha particle has twice the electric charge of the beta particle but deflects less than the
beta in a magnetic field because it
A) moves much slower.
B) moves much faster.
C) has much more inertia.
D) has much less inertia.
Answer: C
14) People who work around radioactivity wear film badges to monitor the amount of radiation
that reaches their bodies. These badges consist of small pieces of photographic film enclosed in a
light-proof wrapper. What kind of radiation do these devices monitor?
A) Alpha radiation
B) Beta radiation
C) Gamma radiation
D) all of the above
Answer: C
15) Why would you expect alpha particles to be less able to penetrate materials than beta
particles of the same kinetic energy?
A) Alpha particles pick up electrons to become harmless helium atoms.
B) Alpha particles carry twice the electric charge.
C) Alpha particles move much slower for a given kinetic energy.
D) Two of the above answers are reasonable.
Answer: D
16) Which of the following statements about radiation is true?
A) Radiation can be a useful tool. Like fire, it is only dangerous when misused.
B) Radiation is new: It is a man-made phenomenon.
C) Radiation has no beneficial health applications.
D) all of the above
E) only A or B
Answer: A
17) Which of the following sources of radiation provides most of our yearly exposure?
A) background radiation
B) smoke detectors
C) living near nuclear power plants
D) televisions (cathode ray tubes)
E) dental and medical X-rays
Answer: A
18) Which of the following professions would likely have the highest occupational exposure to
radiation per year?
A) airline pilot
B) quarterback for the Denver Broncos
C) center for the L.A. Lakers
D) deep sea diver
E) lifeguard
Answer: A
19) What is a rem?
A) A rem is a unit for measuring radiation exposure.
B) A rem is the maximum exposure limit for occupational safety.
C) Rem stands for Rapid Electron Motion.
D) A rem is the number of radiation particles absorbed per second.
E) Rem is an '80s rock group.
Answer: A
20) Which of the following statements about radiation is true?
A) Your body contains a number of radioactive isotopes.
B) One rem is enough to kill approximately 50 percent of the average population.
C) Radiation damages cells beyond repair.
D) Several small exposures over time has the same negative effect as one large exposure that
totals the same amount.
E) Radiation can make you glow in the dark.
Answer: A
21) Which of the following emits more radiation?
A) a coal-fired power plant
B) a nuclear power plant
C) fallout from nuclear tests in the '50s and '60s
D) a television set
E) a computer monitor
Answer: A
22) Which of the following might be considered a viable application of a radioactive tracer?
A) adding a stream of radioisotopes to waste water to examine where pollution goes when it
flows into the ocean
B) placing radioactive sources around a room to trace the location of people as they move
through the room
C) embedding a radioactive plug in a valuable necklace so that its location can be determined
using a Geiger counter
D) all of the above
E) none of the above
Answer: A
23) Which of the following types of radiation might be best for medical imaging?
A) Gamma radiation would be best because it penetrates the best.
B) Alpha radiation would be best because it penetrates the least and therefore does the least
damage.
C) Beta radiation would be best because it can be measured electrically.
D) Only X-rays are used for medical imaging.
E) none of the above
Answer: A
24) In the 19th century the famous physicist Lord Kelvin estimated the age of Earth to be much
much less than its present estimate. What information did Kelvin not have to account for his
error?
A) Lord Kelvin knew only classical physics and had no knowledge of anthropological dating.
B) Lord Kelvin had no knowledge of radio waves for measuring distance and age of planets
since they have not yet been introduced into science.
C) Lord Kelvin was not aware of radioactive decay, a source of energy to keep Earth warm for
billions of years.
D) Lord Kelvin never gave any estimate of the age of Earth.
Answer: C
25) A sample of radium is usually a little warmer than its surroundings because
A) it efficiently absorbs and releases energy from sunlight.
B) its atoms are continually being struck by alpha and beta particles.
C) it is radioactive.
D) it emits alpha and beta particles.
Answer: B
26) Which type of radiation from cosmic sources predominates on the inside of a high-flying
commercial airplane: alpha, beta, or gamma?
A) alpha radiation
B) beta radiation
C) gamma radiation
D) None of these predominate as all three are abundant.
Answer: C
27) You and your friend journey to the mountain foothills to get closer to nature and escape such
things as radioactivity. While bathing in the warmth of a natural hot spring she wonders aloud
how the spring gets its heat. What do you tell her? You tell her that the hot water is the result of
A) industrial thermal pollution.
B) radioactivity.
C) chemical reactions involving the atomic nucleus.
D) nuclear fission.
Answer: B
28) Coal contains only minute quantities of radioactive materials, yet there is more
environmental radiation surrounding a coal-fired power plant than a fission power plant. This
indicates that
A) the coal-fired power plant's radiation shields need to be strengthened.
B) the coal-fired power plant has been contaminated.
C) the coal-fired power plant contains none of the radiation it releases.
D) the news media is biased in its coverage.
Answer: C
29) A friend produces a Geiger counter to check the local background radiation. It ticks. Another
friend, who normally fears most that which is understood least, makes an effort to keep away
from the region of the Geiger counter and looks to you for advice. What do you say?
A) Run away as fast as you can!
B) The Geiger counter is emitting radiation.
C) The Geiger counter is detecting naturally occurring radiation from your body.
D) Wear heavy clothes.
Answer: C
30) When food is irradiated with gamma rays from a cobalt-60 source, does the food become
radioactive? Why?
A) Yes. This is why irradiation with cobalt-60 is no longer approved by the FDA.
B) Yes. However, the radioactivity resulting is well below the danger level established by the
FDA.
C) No. The gamma rays do not have sufficient energy to initiate the nuclear reaction in the atoms
of the food.
D) Yes and No. Although the gamma rays initiate the nuclear reaction the radioactivity does not
show up until the food is ingested.
Answer: C
13.2 The Atomic Nucleus and the Strong Force
1) Which of the following statements best describes why a large nucleus is more likely to
undergo radioactive decay?
A) The nuclear forces are not as strong as the repulsive electrical forces between nucleons.
B) The nuclear force between the nucleons are very strong and squeeze out other nucleons.
C) The nucleon-nucleon attraction is stronger than the proton-proton repulsion.
D) The proton-proton repulsion cannot overcome the nucleon attraction.
E) All nuclei are equally likely to undergo radioactive decay.
Answer: A
2) Which of the following statements best describes the strong nuclear force?
A) The force is very strong but has a very short range.
B) The electrical force is stronger than the nuclear force.
C) The force is very strong and works over very long distances.
D) The strength of the force increases with distance.
E) The force has two sides: the light side and the dark side.
Answer: A
3) Which of the following statements best describes the role of neutrons in the nucleus?
A) The neutrons stabilize the nucleus by attracting other nucleons.
B) The neutrons stabilize the nucleus by forming bonds with other neutrons.
C) The neutrons stabilize the nucleus by attracting protons.
D) The neutrons stabilize the nucleus by balancing charge.
E) The neutrons stabilize the nucleus by adding mass.
Answer: A
4) Why is the combination of two protons and two neutrons stable, but two protons and one
neutron is not?
A) There are not enough neutrons to overcome the electrical repulsion of the protons.
B) There are not enough neutrons to overcome the nuclear repulsion of the protons.
C) The nuclear attraction between protons is greater than that between neutrons.
D) The electrical repulsion between the two protons is greater in one case than the other.
E) none of the above
Answer: A
5) The element uranium (U, atomic no. = 92) often has 146 (or more) neutrons but it will still
undergo radioactive decay. Which statement might best describe why?
A) The attractive force of the nucleons has a limited range.
B) The isolated neutron is not stable and will undergo spontaneous transformation into a proton
and an electron.
C) The force is strong with U, but tainted with the dark side it is.
D) both A and B
E) none of the above
Answer: D
6) Why are smaller nuclei such as carbon-14 often radioactive? (carbon-12 is the most common
and most stable form of carbon.)
A) The attractive force of the nucleons has a limited range.
B) The isolated neutron is not stable and will undergo spontaneous transformation into a proton
and an electron.
C) Hmmm... mysterious are the ways of the force.
D) both A and B
E) none of the above
Answer: B
7) Just after an alpha particle leaves the nucleus, would you expect it to speed up? Why?
A) No. Once the alpha particle leaves the nucleus it is slowed by the repulsion of the next closest
atom's nucleus.
B) No. As the alpha particle leaves the nucleus it is slowed by the constant attraction of the
electrons surrounding the nucleus.
C) Yes. Once the alpha particle leaves the nucleus there are no more forces acting on it and it
therefore accelerates.
D) Yes. Once the alpha particle leaves the nucleus it accelerates because of mutual electric
repulsion with the nucleus from which it escaped.
Answer: D
8) A pair of protons in an atomic nucleus repel each other, but they are also attracted to each
other. Why?
A) The pair repel each other by nuclear force but attract one another by an electrical force.
B) The pair repel each other since they are both positively charges but they are held together by
much stronger forces known as quarks.
C) The pair attract each other by nuclear force but also repel one another by a weaker electrical
force.
D) Although it is known that protons repel each other at short distances because of like charge, it
is not known what actually holds protons together in the nucleus because we have never seen the
nucleus of an atom.
Answer: C
9) If an atom has 104 electrons, 157 neutrons, and 104 protons, what is its approximate atomic
mass?
A) The approximate atomic mass is 365.
B) The approximate atomic mass is 261.
C) The approximate atomic mass is 157.
D) The approximate atomic mass is cannot be determined with the information given.
Answer: B
10) In bombarding atomic nuclei with proton "bullets," the protons must be accelerated to high
energies to make contact with the target nuclei
A) because the target nuclei are so small.
B) because the target nuclei are negatively charged.
C) in order to penetrate through the electrons that surround each target nucleus.
D) because the target nuclei are positively charged.
Answer: D
11) What evidence supports the contention that the strong nuclear force is stronger than the
electrical interaction at short inter-nuclear distances?
A) Protons are able to exist side-by-side within an atomic nucleus.
B) Neutrons spontaneously decay into protons and electrons.
C) Uranium deposits are always slightly warmer than their immediate surroundings.
D) The radio interference that arises adjacent to any radioactive source.
Answer: A
12) Your friend says that the helium used to inflate balloons is a product of radioactive decay.
Another friend says no way. With whom do you agree?
A) If helium were a product of radioactive decay, we would all be radioactive. Agree with the
friend that says "no way."
B) Radioactive decay produces alpha particles, not helium. Agree with the friend that says "no
way."
C) Your first friend is correct. Radioactive isotopes emit alpha particles which, in turn, capture
electrons and become helium atoms.
D) Helium is an element of the periodic table, not some product of any reaction. Agree with the
friend that says "no way."
Answer: C
13.3 Half-Life and Transmutation
1) What is a half-life?
A) It is the time it takes for 1/2 of the material to undergo radiodecay.
B) It is the time needed until 1/2 of the radiation is gone.
C) It is the time it takes for 1/2 of the material to decompose.
D) It is half of the lifetime of the radioactivity in a sample.
E) all of the above
Answer: A
2) What property of half-lives makes radioactive material so problematic?
A) There is no known way to shorten a half-life.
B) Radioactivity is limited by the natural decay-time to stable isotopes.
C) All half-lives are long.
D) There is no known way to measure half-lives with any accuracy.
E) both A and B
Answer: E
3) If a material has a half-life of 24 hours, how long do you have to wait until the amount of
radioisotope is 1/4 its original amount?
A) 12 hours
B) 24 hours
C) 48 hours
D) 72 hours
E) practically forever, but it may be safe by then
Answer: C
4) If three samples have the half-lives listed below, which is the most radioactive?
A) a sample with a half-life of 20 minutes
B) a sample with a half-life of 20 hours
C) a sample with a half-life of 20 years
D) a sample with a half-life of 20 million years
E) none of the above
Answer: A
5) If three samples have the half-lives listed below, which sample would remain radioactive the
longest?
A) a sample with a half-life of 20 minutes
B) a sample with a half-life of 20 hours
C) a sample with a half-life of 20 years
D) a sample with a half-life of 20 million years
E) none of the above
Answer: D
6) What is transmutation?
A) changing one element into another by adding or removing protons from the nucleus
B) changing one element into another by adding or removing electrons from the nucleus
C) changing one element into another by adding or removing neutrons from the nucleus
D) a process that emits radiation
E) alteration in DNA due to radioactivity
Answer: A
7) Which of the following nuclear equations correctly describes alpha emission?
E) none of the above
Answer: A
8) Which of the following nuclear equations correctly describes beta emission?
E) none of the above
Answer: E
9) Which of the following nuclear equations correctly describes beta emission?
E) none of the above
Answer: A
10) Which of the following nuclear equations correctly describes alpha emission?
E) none of the above
Answer: E
11) Complete the following nuclear equation:
Tl →
A)
Pb + ??
e
B) He
C) gamma ray
D) both A and B
E) none of the above
Answer: A
12) Complete the following nuclear equation:
Bi →
A)
e
B) He
Tl + ??
C) gamma ray
D) both A and B
E) none of the above
Answer: B
13) Complete the following nuclear equation:
Bi → ?? +
A)
Po
B)
Pb
C)
Pb
D)
Th
e
E) none of the above
Answer: A
14) Complete the following nuclear equation:
Po → ?? + He
A)
Po
B)
Pb
C)
Pb
D)
Rn
E) none of the above
Answer: B
15) Complete the following nuclear equation:
?? →
Rn + He
A)
Ra
B)
At
C)
Po
D)
Rn
E) none of the above
Answer: A
16) Complete the following nuclear equation:
?? →
At +
A)
Ra
B)
At
C)
Po
D)
Rn
e
E) none of the above
Answer: C
17) Which type of radiation is being emitted in the following incomplete nuclear equation:
Pb →
Bi + ??
A) alpha
B) beta
C) gamma
D) A and B
E) none of the above
Answer: B
18) Which type of radiation is being emitted in the following incomplete nuclear equation:
Po →
Pb + ??
A) alpha
B) beta
C) gamma
D) A and B
E) none of the above
Answer: A
1
9) If carbon-14 is a beta emitter, what is the likely product of radioactive decay?
A) nitrogen-14
B) carbon-12
C) oxygen-18
D) berrylium-10
E) none of the above
Answer: A
20) Which type of radiation—alpha, beta, or gamma—results in the greatest change in atomic
mass number?
A) alpha radiation
B) beta radiation
C) gamma radiation
D) They all result in the same change in atomic mass number.
Answer: A
21) Which type of radiation—alpha, beta, or gamma—results in the least change in atomic
number?
A) alpha radiation
B) beta radiation
C) gamma radiation
D) They all result in the same change in atomic mass number.
Answer: C
22) When the isotope bismuth-213 emits an alpha particle, what new element results?
A) lead
B) platinum
C) polonium
D) thallium
Answer: D
23) When
Ra decays by emitting an alpha particle, what is the atomic number of the resulting
nucleus? What is the resulting atomic mass?
A) atomic number = 86; atomic mass = 222
B) atomic number = 87; atomic mass = 226
C) atomic number = 86; atomic mass = 224
D) atomic number = 87; atomic mass = 224
Answer: A
24) When
Po emits a beta particle, it transforms into a new element. What are the atomic
number and atomic mass of this new element?
A) atomic number = 84; atomic mass = 219
B) atomic number = 86; atomic mass = 214
C) atomic number = 85; atomic mass = 218
D) atomic number = 82; atomic mass = 214
Answer: C
25) How is it possible for an element to decay "forward in the periodic table"--that is, to decay to
an element of higher atomic number?
A) When the decay is instigated by a collision with a proton.
B) As a beta particle is released, a neutron transforms into a proton.
C) This only occurs during nuclear fusion.
D) It is not possible. Radioactive decay always results in an isotope with the same or lower
atomic number.
Answer: B
26) Elements above uranium in the periodic table do not exist in any appreciable amounts in
nature because they have short half-lives. Yet there are several elements below uranium in
atomic number with equally short half-lives that do exist in appreciable amounts in nature. How
can you account for this?
A) These are isotopes formed by living bodies.
B) These isotopes were placed in nature by the testing of nuclear bombs.
C) These isotopes were formed from the fusion of even smaller isotopes.
D) These isotopes result from the radioactive decay of uranium.
Answer: D
27) How many alpha particles are emitted in the series of radioactive decay events from a U-238
nucleus to a Pb-206 nucleus?
A) 32
B) 16
C) 8
D) 4
Answer: C
28) If a nucleus of
Th absorbs a neutron and the resulting nucleus undergoes two successive
beta decays (emitting electrons), what nucleus results?
A) americium-232
B) plutonium-232
C) thorium-233
D) uranium-233
Answer: D
29) If Uranium-234 decays via alpha emission, what is the likely product of radioactive decay?
(U, atomic no. = 92)
A)
Th
B)
Np
C)
Th
D)
Np
E) none of the above
Answer: A
13.4 Radiometric Dating
1) How come an animal's carbon-14 levels do not start to decrease until it dies?
A) because it constantly replenishes its carbon-14 supply by eating plants with carbon-14 in them
B) because it constantly replenishes its carbon-14 supply by breathing air with carbon-14 in it
C) because it is constantly being bombarded with cosmic rays
D) carbon-14 only starts to decay after the animal dies
E) the carbon-14 levels do not decrease because the carbon-13 in its skin protects it from cosmic
rays
Answer: A
2) How can a half-life be used to tell the age of a sample?
A) The half-life of an isotope is constant.
B) The amount of radioactive form depends on the amount of radiation in the surroundings.
C) The ratio between the radioactive form and the stable form depends on the archaeological
record.
D) The ratio between the radioactive form and stable form varies regularly with time.
E) both C and D
Answer: D
3) The half-life of carbon-14 is 5,730 years. A sample is found to have one-eighth the original
amount of carbon-14 in it. How old is the sample?
A) 5,730 years
B) 716 years
C) 4,5800 years
D) 17,200 years
E) none of the above
Answer: D
4) Which of the following statements about carbon-14 dating is true?
A) Carbon-14 dating is very accurate because the amount of carbon-14 in the atmosphere is
constant.
B) Carbon-14 can be used to date anything younger than 50,000 years.
C) Carbon-14 dating can be used to date stone tools as well as bone.
D) all of the above
E) none of the above
Answer: E
5) Why wouldn't you use carbon-14 dating on a piece of shell that was estimated to be 1 million
years old?
A) Sea shells do not have radioisotopes.
B) Carbon dating is only useful on plants.
C) Uranium dating is better for items older than 1/2 million years.
D) Carbon dating can only be used on items that were once alive.
E) The amount of radioactive carbon in the sample would probably too small to measure.
Answer: E
6) Radium-226 is a common isotope on Earth, but has a half-life of about 1600 years. Given that
Earth is some 5 billions years old, why is there any radium at all?
A) Radium-226 is one of several self-trans mutating isotopes of the elements of the periodic
table and is able to replenish itself so that it is never depleted.
B) Radium-226 and Radium-218 undergo a series of transmutation reactions of alpha and beta
decay to repeatedly become one another approximately every 1600 years.
C) Radium-226 is a "daughter" isotope and the result of the radioactive decay of uranium.
D) Radium-226 and Astatine-218 are converted back and forth via transmutation to one another
at each of their respective half-life cycles.
Answer: C
7) Why is the carbon-14 dating not accurate for estimating the age of materials more than 50,000
years old?
A) This form of radioactive dating is only accurate back 1,400 years.
B) The concentration of carbon-14 in a body after 50,000 years is too low.
C) Living organisms are too decomposed after 50,000 years.
D) Actually, carbon-14 dating is accurate back to around 5 million years ago.
Answer: B
8) The age of the Dead Sea Scrolls was found by carbon-14 dating. Could this technique have
worked if they were carved in stone tablets? Explain.
A) Yes, because there are appreciable levels of carbon even in stone.
B) No, this method of dating requires a material that was once living.
C) Yes, because X-ray images could be collected instead.
D) No, the stones in the arid environment of the Dead Sea would have lost all of their carbon-14
by now.
Answer: B
9) A certain radioactive element has a half-life of one hour. If you start with a 1-g sample of the
element at noon, how much of this same element will be left at 3:00 PM?
A) 0.5 gram
B) 0.25 gram
C) 0.125 gram
D) 0.0625 gram
Answer: C
10) The isotope Cesium-137, which has a half-life of 30 years, is a product of nuclear power
plants. How long will it take for this isotope to decay to about one-sixteenth its original amount?
A) 480 years
B) 240 years
C) 120 years
D) 960 years
Answer: C
13.5 Nuclear Fission
1) Otto Hahn and Fritz Strassmann discovered fission by bombarding uranium with neutrons.
Their discovery was made possible by finding one of the fission products, barium (Ba, atomic
no. = 56). What is a reasonable explanation for why they were unable to initially observe the
other product, krypton (Kr, atomic no. = 36)
A) Krypton is a noble gas and it may have diffused out of the sample.
B) The isotope of krypton generated might have a short half-life and had undergone radioactive
decay to some other element.
C) Krypton is a noble gas and therefore chemically unreactive, making it difficult to characterize
by chemical means.
D) both A and B
E) all of the above
Answer: E
2) Which of the following statements about fission is true?
A) The amount of energy released in the fission of large nuclei is very large.
B) The amount of energy released in the fusion of small nuclei is very large.
C) Bombarding a nucleus with neutrons always leads to fission.
D) The fragments of a fusion reaction are always the same size.
E) none of the above
Answer: A
3) Which of the following statements about chain reactions is true?
A) The key requirement for a chain reaction is that more neutrons are produced than are
absorbed.
B) Three or more neutrons must be released to sustain a chain reaction.
C) Only uranium isotopes are capable of supporting a chain reaction.
D) It is not possible to stop or control a chain reaction once it has been started.
E) A chain reaction will only take place when a critical mass of material has been assembled.
Answer: A
4) Which of the following statements best describes a critical mass?
A) A critical mass is the minimum amount of material that will undergo nuclear detonation.
B) A critical mass is the minimum amount of material that will spontaneously undergo a chain
reaction.
C) A critical mass cannot be assembled from smaller, noncritical pieces of material.
D) A critical mass will detonate when it is separated into subcritical pieces.
E) none of the above
Answer: A
5) How do fission power plants work?
A) The heat from a nuclear reaction is used to boil water.
B) The neutrons from a nuclear reaction undergo fusion with water to produce hydrogen gas,
which drives a turbine.
C) The electrons from a nuclear reaction are harnessed to produce an electrical current.
D) The krypton gas generated in the fission process is used to drive a turbine.
E) none of the above
Answer: A
6) Which of the following is a major advantage of nuclear-fission-based power plants?
A) The amount of energy per kilogram of fuel is greater than any other fuel source.
B) The byproducts of the fission process are radioactive and have very long half-lives.
C) The reactors can be used to produce their own fuel.
D) The power plants are complex and there are many safety requirements to prevent
contamination of the environment.
E) A and C
Answer: E
7) Which of the following is a major disadvantage of nuclear-fission-based power plants?
A) The reactors can be used to produce their own fuel.
B) The byproducts of the fission process are radioactive and have very long half-lives.
C) The amount of energy per kilogram of fuel is greater than any other fuel source.
D) The power plants are complex and there are many safety requirements to prevent
contamination of the environment.
E) B and D
Answer: E
8) Why doesn't uranium ore spontaneously undergo a chain reaction?
A) Uranium ore must be "weapons' grade" in order for it to undergo chain reaction.
B) Uranium ore is mostly non-fissionable isotope U-238 and undergoes a chain reaction only if
mixed with a moderator to slow down the neutrons.
C) Uranium ore does spontaneously undergo slow chain reaction over time finally resulting in it
becoming lead.
D) Uranium ore, mostly U-235, must be enriched with U-238 in order for it to undergo a chain
reaction.
Answer: B
9) Why will nuclear fission probably not be used directly for powering automobiles?
A) Massive shielding would be required to protect against radioactivity exposure.
B) Radioactive wastes could not be adequately controlled.
C) It's more practical for cars to use the electricity generated by nuclear fission power plants.
D) All of the above are true.
Answer: D
10) Does the average distance that a neutron travels through fissionable material before escaping
increase or decrease when two pieces of fissionable material are assembled into one piece? Does
this assembly increase or decrease the probability of an explosion?
A) The average distance increases while the probability of an explosion also increases.
B) The average distance decreases while the probability of an explosion decreases.
C) The average distance increases while the probability of an explosion decreases.
D) The average distance decreases while the probability of an explosion increases.
Answer: A
11) Which shape is likely to need more material for a critical mass, a cube or a sphere? Why?
A) a sphere because it has the greater surface area to volume ratio.
B) a sphere because it has the smaller surface area to volume ratio.
C) a cube because it has the greater surface area to volume ratio.
D) a cube because it has the smaller surface area to volume ratio.
Answer: C
12) A neutron makes a better nuclear bullet than a proton or an electron because it
A) has the greatest mass.
B) carries no electrical charge.
C) can be accelerated by electromagnetic fields.
D) all of the above
Answer: B
13) Why does plutonium not occur in appreciable amounts in natural ore deposits?
A) Most naturally occurring plutonium deposits have already been depleted in the creation of
nuclear weapons.
B) Plutonium is strictly a human-made element.
C) Any plutonium initially in the earth's crust has long since decayed.
D) Plutonium loses electrons to form positively charged particles that have long since washed
into the oceans.
Answer: C
14) Why is carbon better than lead as a moderator in nuclear reactors?
A) Carbon produces the high energy, high speed neutrons necessary for maintaining the nuclear
chain reaction.
B) Carbon slows down the neutrons making them more effective in stimulating the nuclear chain
reaction.
C) Lead absorbs the neutrons rather than allowing them to rebound to maintain the nuclear chain
reaction.
D) Lead slows down the neutrons making them less effective in stimulating the nuclear chain
reaction.
Answer: B
15) After a uranium fuel rod reaches the end of its fuel cycle (typically 3 years) most of its
energy comes from the fissioning of plutonium because
A) fissionable Pu-239 is formed as the U-238 absorbs neutrons from the fissioning U-235.
B) fissionable Pu-239 is formed as the U-235 absorbs neutrons from the fissioning U-238.
C) fissionable Pu-239 is formed as the U-238 absorbs alpha particles from the fissioning U-235.
D) fissionable Pu-239 is formed as the U-235 absorbs alpha particles from the fissioning U-238.
Answer: A
16) Uranium-235 releases an average of 2.5 neutrons per fission, while plutonium-239 releases
an average of 2.7 neutrons per fission. Which of these elements might you therefore expect to
have the smaller critical mass?
A) plutonium-239
B) uranium-235
C) The number of neutrons per fission will not effect the size of critical mass.
D) The critical mass of these elements cannot be determined from only the number of neutrons
per fission.
Answer: A
17) If a nucleus of
Th absorbs a neutron and the resulting nucleus undergoes two successive
beta decays (emitting electrons), what nucleus results?
A) Americium-232
B) Plutonium-232
C) Thorium-233
D) Uranium-233
Answer: D
18) The original reactor built in 1942 was just "barely" critical because the natural uranium that
was used contained less than 1% of the fissionable isotope U-235 (half life 713 million years).
What if, in 1942, the Earth had been 9 billion years old instead of 4.5 billion years old? Would
this reactor have reached critical stage with natural uranium? Why?
A) No. The age of the Earth has nothing to do with the reactor reaching critical stage with U-235.
B) No. 1% of the fissionable isotope U-235 is insufficient for the reactor to reach critical stage
no matter what the age of the Earth.
C) Yes. If the Earth had been twice as old there would have then been twice as much fissionable
U-235 present and the reactor would have reached critical stage.
D) No. The increased age of the Earth would mean that there would be a much smaller
percentage of U-235, thus not enough for the reactor to reach critical stage.
Answer: D
13.6 Mass-Energy Equivalence: E = mc2
2
1) What does Einstein's energy equation (E = mc ) say about the energy that is derived from
nuclear fission reactions?
A) The energy released is due to the missing mass of the products compared to the mass of the
starting materials.
B) The energy is proportional to the mass of the atom undergoing fission.
C) The energy is derived from the light that is emitted when the atom splits.
D) The energy equation does not apply towards fission, only fusion.
E) none of the above
Answer: A
2) Which of the following statements regarding a nucleon is true in regards to nuclear reactions?
A) A nucleon inside a nucleus has a lower mass than a nucleon outside of the nucleus.
B) The number of nucleons changes in a nuclear reaction, therefore the mass changes.
C) A nucleon has a higher energy inside a nucleus, and releases it when it undergoes nuclear
reactions.
D) A nucleon's mass is constant.
E) A nucleon is more stable outside the nucleus.
Answer: A
3) Which of the following statements regarding a nucleon is true?
A) Attraction between nucleons changes their mass.
B) The mass of a nucleon depends on which nucleus it is in.
C) Some of the mass of a nucleon can be converted into energy by breaking certain nuclei.
D) both A and C
E) all of the above
Answer: E
4) Which of the following does not describe a nuclear fission reaction?
A) The number of nucleons in the products is different from the number of nucleons in the
starting material.
B) The mass of the products is less than the mass of the reactants.
C) The energy released is proportional to the mass difference in the system.
D) All of the above describe a fusion reaction.
E) None of the above describe a fusion reaction.
Answer: A
5) Which of the following elements is the most stable from a nuclear point of view?
A) iron
B) hydrogen
C) argon
D) uranium
E) All are equally stable.
Answer: A
6) Why might the following nuclear reaction not be very good for energy production in a fission
reactor?
U→
Ba +
Kr + 1 neutron
A) The material only produces one neutron so the chain reaction will not be very efficient.
B) The products are too large.
C) There are too many products produced.
D) The mass of the byproducts is too high and therefore the energy released will not be high
enough.
E) Interatomic attraction between the products will impede the efficient separation of the atoms
from the unstable nuclei.
Answer: A
7) Why might the following nuclear reaction not be very good for energy production in a fission
reactor?
U→
Th + He + 3 neutrons
A) The material only produces a few neutrons so the chain reaction will not be very efficient.
B) The reactants are too small to obtain much energy from the missing mass due to the strong
nuclear force.
C) The products are not the right size to obtain much energy from missing mass due to strong
nuclear force.
D) The mass of the byproducts is too high and therefore the energy released will not be large
enough.
E) Interatomic attraction between the products will impede the separation of the atoms from the
unstable nuclei.
Answer: C
8) Why might the following nuclear reaction not be very good for energy production in a fission
reactor?
Fe →
Si +
Mg + 3 neutrons
A) The material only produces a few neutrons so the chain reaction will not be very efficient.
B) The reactants are too small to obtain energy from the missing mass due to strong nuclear
force.
C) The products are not the right size to obtain much energy from the missing mass due to the
strong nuclear force.
D) The mass of the byproducts is too high and therefore the energy released will not be high
enough.
E) Interatomic attraction between the products will impede the separation of the atoms from the
unstable nuclei.
Answer: B
9) To predict the approximate energy release of either a fission or a fusion reaction, explain how
a physicist uses a table of nuclear masses and the equation E = m .
A) find the change in mass and divided by the speed of light squared
B) find the change in mass and multiply by the speed of light squared
C) find the change in mass, square it, and multiply by the speed of light
D) take the square root of the change in mass and multiply by the speed of light
Answer: B
10) Light nuclei can be split. For example, a deuteron, which is a proton-neutron combination,
can split into a separate proton and separate neutron. Does such a process yield energy or cost
energy? Why?
A) Yields energy. Splitting nuclei of any sort is a basic example of a nuclear reaction releasing
massive amounts of energy.
B) Neither. The amount of energy required to split the light nuclei is exactly the same as that
released. This is the basis of the Law of Conservation of Energy.
C) Costs energy. This fact is consistent with the sum of the masses of the separated proton and
neutron being greater than the mass of the original deuteron.
D) Yields energy. This fact is consistent with the sum of the masses of the separated proton and
neutron being less than the mass of the original deuteron.
Answer: C
13.7 Nuclear Fusion
1) Which are older, the atoms in the body of an elderly person or those in the body of a baby?
A) a baby because this is surely a trick question
B) an elderly person because they have been around much longer
C) They are of the same age, which is appreciably older than the solar system.
D) It depends upon their diet.
Answer: C
2) Where did the atoms that make up a newborn baby originate?
A) in the womb of the baby's mother
B) in the digestion of the food that the mother ate
C) in the earth through geological processes
D) in the explosions of ancient stars
Answer: D
3) What is the main technical difficulty in dealing with fusion reactions?
A) The amount of energy needed to overcome the electrical repulsion of the reactants is
extremely high.
B) The reactants are highly toxic and extremely radioactive.
C) The mass of the reactants is less than the mass of the products.
D) It isn't possible to artificially generate the conditions needed for fusion.
E) none of the above
Answer: A
4) Which of the following statements about fusion is true?
A) Fusion reactions have no critical-mass requirement.
B) Fusion is easier than fission.
C) Fusion reactions can be easily controlled to make energy.
D) Fusion produces no harmful radiation.
E) none of the above
Answer: A
5) Where does the earth receive most of its energy?
A) external fusion
B) internal fusion
C) internal fission
D) external fission
E) internal combustion
Answer: A
6) Which of the following statements about fusion is the most accurate?
A) The mass of the products is less than the mass of the reactants.
B) The mass of the reactants is less than the mass of the products.
C) A nuclear fusion will always release energy.
D) Overcoming the strong nuclear force results in the release of a large amount of energy.
E) Fission releases more energy than fusion.
Answer: A
7) Why might the following nuclear reaction not be very good for energy production in a fusion
reactor?
Fe +
Fe →
Te
A) The material only produces a few neutrons so the chain reaction will not be very efficient.
B) The reactants are too stable and it would cost energy to produce the product due to strong
nuclear force.
C) The products are not the right size to obtain any energy from the missing mass due to the
strong nuclear force.
D) The mass of the byproducts is too high and therefore the energy released will not be high
enough.
E) Interatomic attraction between the products will impede the separation of the atoms from the
unstable nuclei.
Answer: B
8) Which process would release energy from gold, fission or fusion? From carbon?
A) gold: fission; carbon: fusion
B) gold: fusion; carbon: fission
C) gold: fission; carbon: fission
D) gold: fusion; carbon: fusion
Answer: A
9) If uranium were to split into three segments of equal size instead of two, would more energy
or less energy be released?
A) Less energy would be released because of less mass per nucleon.
B) Less energy would be released because of more mass per nucleon.
C) More energy would be released because of less mass per nucleon
D) More energy would be released because of more mass per nucleon.
Answer: C
10) Is the mass of an atomic nucleus greater or less than the sum of the masses of the nucleons
composing it? Why don't the nucleon masses add up to the total nuclear mass?
A) Greater. We need to add the masses of the surrounding electrons to the masses of the
nucleons.
B) Neither. The mass of the atomic nucleus is exactly the sum of the masses of the nucleons.
C) Less. The individual nucleons have greater mass when separated from the nucleus. This
additional mass is a result of the energy of separation.
D) Greater. The mass of the atomic nucleus also has mass of the "atomic glue" that holds the
nucleons together in the nucleus.
Answer: C
11) Which produces more energy, the fissioning of a single uranium nucleus or the fusing of a
pair of deuterium nuclei? Why?
A) Fusing a pair of deuterium nuclei produces more energy because, unlike fission, there is no
radioactive waste product.
B) Fissioning a single uranium nucleus produces more energy since its mass is much greater than
that of a pair of deuterium nuclei.
C) Both the fissioning of a single uranium nucleus and the fusing of a pair of deuterium nuclei
produce the same amount of energy since the resulting products are the same.
D) Neither the fissioning of a single uranium nucleus nor the fusing of a pair of deuterium nuclei
produce any net amount of energy. On the contrary, both processes require more energy than
they produce.
Answer: B
12) If a fusion reaction produces no appreciable radioactive isotopes, why does a hydrogen bomb
produce significant radioactive fallout?
A) The fallout is only the radioactive remnants of the bomb's structure and casing.
B) It is a misconception that fusion reactions produce no appreciable radioactive isotopes.
Therefore, radioactive fallout is unavoidable.
C) The radioactive fallout is a result of the fission reaction used to ignite the thermonuclear
fusion reaction.
D) Once a hydrogen bomb is exploded, all matter within nearly 100 miles becomes radioactive
fallout.
Answer: C
13) Explain how radioactive decay has always warmed the earth from the inside, and nuclear
fusion has always warmed the earth from the outside.
A) Much heat was released as matter coalesced to form the earth. This heat resulted in the
production of radioactive isotopes, which still reside within the earth today and are a source of
internal heat. Our primary external source of heat is from the fusion of hydrogen within the sun.
B) The inner Earth is made of fissioning heavy elements while the sun is made of lighter fusing
elements.
C) Radioactive elements have been within Earth since it was created while the sun is made of
fusing hydrogen atoms.
D) All of the above are reasonable answers.
Answer: C
14) Ordinary hydrogen is sometimes called a perfect fuel, because of its almost unlimited supply
on Earth, and when it burns, harmless water is the product of the combustion. So why don't we
abandon fission energy and fusion energy, not to mention fossil-fuel energy, and just use
hydrogen?
A) The oil companies have lobbied the federal government to continue fossil fuel usage because
it would mean huge profit losses for all the major oil conglomerates.
B) The conversion of current energy consuming vehicles and other machinery to hydrogen,
although simple, is going to be very costly to the consumer and difficult to legislate.
C) The political, economic, and corporate pressures being exerted to oppose abandoning the
other energy sources are the only obstacles to moving to the use of hydrogen as the nation's
primary energy source.
D) Hydrogen represents a viable solution for stored energy but not as a general energy source
since obtaining the hydrogen from water requires more energy than is produced when you burn
it.
Answer: D
15) What are some of the optimistic worldwide changes that may follow the advent of successful
fusion reactors?
A) Economies will be geared to relative abundance rather than scarcity.
B) Humans will have more opportunities to focus on social issues, such as world hunger.
C) There will be fewer hostilities between nations.
D) all of the above
Answer: D
Test Bank for Conceptual Physical Science
Paul Hewitt, John Suchocki, Leslie Hewitt
9780321752932, 9780134060491
