unit 4
each fission en=vent produces:
1 or more neutrons
a large nuclei with ___ or more protons arent stable
84
A sample originally contained 1.28 g of a radioisotope. It now contains 1.12 g of its daughter isotope. How many half-lives have passed since the sample originally formed? A:3 B:4 C:8 D:16
A
A small amount of americium-241 is used in smoke detectors. A stream of radiation flows between two electrodes. If smoke interrupts the stream, the alarm goes off. What feature of the radioisotope americium-241 would be most helpful for the smoke detector to work? A:long half-life B:short half-life C:over-sensitive detection D:less sensitive detection
A
According to most scientists, cold fusion A:will not be a practical source of energy on Earth. B:would be a practical source of energy on Earth if it were less expensive. C:will be a practical source of energy on Earth within the next few decades. D:will always continue to be a practical source of energy on Earth.
A
An isotope undergoes radioactive decay by emitting radiation that has a -1 charge. What other characteristic does the radiation have? A:some shielding required B:no mass C:large mass D:high penetrating power
A
What can form as a result of a chemical reaction? A:compounds B:isotopes C:alpha particles D:beta particles
A
Which answer choice best explains why uranium-238 can be used in power plants to generate electricity? A:Nuclides of uranium-238 decay over time. They release large amounts of energy as their nuclei break apart. B:Nuclides of uranium-238 are extremely stable. They can absorb large amounts of energy without breaking apart, so they rarely need to be replaced. C:Because atoms of uranium-238 have many more electrons than protons, they release steady streams of electric current. D:Because atoms of uranium-238 have many more protons than neutrons, they attract large numbers of electrons from the surrounding environment.
A
Why is it important for scientists to replicate each other's experiments? A:to determine if important scientific results are repeatable B:to help the research of other scientists C:to determine if slight alterations in the experiment can affect the result D:to further their own research
A
what is an isotope
An isotope of a chemical element is an atom that has a different number of neutrons than the standard for that element. The atomic number is the number of protons in an atom's nucleus.
How is half-life most likely used with respect to this fossil? A:to find the mass of the fossil B:to find the age of the fossil C:to determine the species shown by the fossil D:to determine if radiation is being emitted from the fossil
B
In reaction A, each sodium atom gives one electron to a chlorine atom. In reaction B, an isotope of oxygen decays to form an isotope of nitrogen. Which statement best describes the energy that is released per gram by these reactions? A:Reaction A releases more energy than reaction B releases. B:Reaction B releases more energy than reaction A releases. C:Reaction A and reaction B release equal amounts of energy. D:Neither reaction A nor reaction B releases energy.
B
Sodium-24 has a half-life of 15 hours. After 45 hours, how much sodium-24 will remain of an original 50.0-g sample? A:5.56 g B:6.25 g C:16.7 g D:25.0 g
B
What is a key difference between chemical and nuclear reactions? A:In chemical reactions, new compounds are formed. In nuclear reactions, compounds are destroyed. B:Chemical reactions involve electron rearrangements. Nuclear reactions involve changes to the nucleus. C:Chemical reactions involve large changes in energy. Nuclear reactions absorb or release small amounts of energy. D:In chemical reactions, only alpha radiation is emitted. In nuclear reactions, alpha, beta, and gamma decay may occur.
B
What is the most penetrating kind of radiation product that can be shielded with aluminum foil? A:alpha particles B:beta particles C:gamma rays D:high-energy photons
B
What property of radioactive nuclear waste makes it so difficult to dispose of responsibly? A:It is extremely volatile. B:It has a very long half-life. C:It is extremely corrosive. D:It emits carbon dioxide.
B
Which can have either a positive charge or a negative charge when they are released during radioactive decay? A:alpha particles B:beta particles C:positrons D:photons
B
Which energy transformation occurs in the core of a nuclear reactor? A:nuclear energy mc027-1.jpg mechanical energy B:nuclear energy mc027-2.jpg thermal energy C:thermal energy mc027-3.jpg nuclear energy D:mechanical energy mc027-4.jpg nuclear energy
B
Which is a characteristic of nuclear fusion but NOT nuclear fission? A:releases large amounts of energy B:is the energy source of stars C:is used in electric power plants D:requires little energy to occur
B
Which is a characteristic of nuclear fusion? A:produces radioactive waste B:involves the collision of two nuclei C:commonly used by humans as an energy source D:requires very little activation energy
B
Which process occurs in a fission nuclear reactor? A:Nuclei combine. B:Nuclei split apart. C:Neutrons combine. D:Neutrons split apart.
B
A scientist is trying to determine whether a certain substance is radioactive. Which question would be most helpful to ask? A:Does the substance have a positive electric charge or a negative electric charge? B:Can the substance be used to generate electricity in a power plant? C:Do the atoms that make up the substance have nuclei that split apart over time? D:Do the nuclei of the substance's atoms contain more neutrons than protons?
C
An atom that has 84 protons and 86 neutrons undergoes a reaction. At the end of the reaction, it has 82 protons and 84 neutrons. What happened to the atom? A:It accepted radiation in a chemical reaction. B:It donated neutrons to another atom in a chemical reaction. C:It emitted an alpha particle in a nuclear reaction. D:It accepted protons in a nuclear reaction.
C
How does critical mass play a role in nuclear reactions? A:It is the minimum amount of material needed to start a fission reaction. B:It is the minimum amount of material needed to start a fusion reaction. C:It is the minimum amount of material needed to sustain a fission reaction. D:It is the minimum amount of material needed to sustain a fusion reaction.
C
How much of a sample remains after three half-lives have occurred? A:1/16 of the original sample B:1/9 of the original sample C:1/8 of the original sample D:1/3 of the original sample
C
The nuclei of most atoms contain multiple protons. Each proton has a positive charge. If objects that have like charges repel each other, why do the protons in the nuclei of most atoms not fly apart? A:The charges of protons and neutrons cancel each other out. B:Electrons outside the nucleus push on protons. C:A strong nuclear force between an atom's protons and neutrons holds together the atom's nucleus. D:Protons experience a more powerful attraction to the negatively charged particles in an atom's nucleus.
C
The original amount of a radioactive sample should be multiplied by which expression to calculate the amount of the sample that remains after n half-lives have passed? A:(1/2)xn B:(1/n)2 C:(1/2)n D:1/(2n)
C
Which answer choice best explains why nuclear reactions release more energy than chemical reactions? A:Electrostatic forces of repulsion are thousands of times stronger than gravitational forces. B:Gravitational forces are thousands of times stronger than electrostatic forces of repulsion. C:The force that binds together protons and neutrons is stronger than the force that attracts and repels protons and electrons. D:The force that attracts and repels protons and electrons is stronger than the force that binds together protons and neutrons.
C
Which component within a nuclear reactor directs neutron bombardment? A:turbine B:generator C:control rod D:chain reaction
C
Which sequence is an example of radioactive decay? A:The nuclei of two hydrogen atoms fuse together, forming a helium nuclide. B:A calcium atom gives its electrons to two fluorine atoms, forming a formula unit of calcium fluoride. C:A polonium isotope becomes a lead isotope when the polonium nuclide emits two protons and two neutrons. D:Energy from an electric current splits a water molecule into two hydrogen atoms and one oxygen atom.
C
Which statement correctly compares chemical reactions with nuclear reactions? A:In chemical reactions, new isotopes are formed. In nuclear reactions, new compounds are formed. B:Chemical reactions can be represented by balanced equations. Nuclear reactions cannot be represented by balanced equations. C:In chemical reactions, small amounts of energy can be absorbed or released. In nuclear reactions, changes in energy are much larger. D:In chemical reactions, only protons and neutrons are affected. In nuclear reactions, only electrons are affected.
C
A(n _____ reaction is a self-sustaining series of chemical reactions in which the products of one reaction are the reactants in the next reaction.
CHAIN
A benefit of using nuclear energy could be the abundance of uranium in nature. Which human risk about mining is the most important to consider? A:the use of a nonrenewable resource B:the location of storage of the radioactive waste C:the cost of setting up a uranium mine operation D:the health hazards that are associated with uranium mining
D
An article about half-lives describes a parent isotope. What is a parent isotope? A:the isotope that forms from the radioactive decay of a less stable isotope B:the isotope that forms from the radioactive decay of a more stable isotope C:an isotope that undergoes radioactive decay to form a less stable isotope D:an isotope that undergoes radioactive decay to form a more stable isotope
D
Carbon-14 has a half-life of 5,730 years. How long will it take for 112.5 g of a 120.0-g sample to decay radioactively? A:5,730 years B:11,460 years C:17,190 years D:22,920 years
D
How are energy and mass connected during the formation of an atom? A:Energy is absorbed, so the mass is increased. B:Energy is released, so the mass is increased. C:Energy is absorbed, so the mass is reduced. D:Energy is released, so the mass is reduced.
D
How is half-life most likely used with respect to this fossil? A:to find the mass of the fossil B:to find the age of the fossil C:to determine the species shown by the fossil D:to determine if radiation is being emitted from the fossil
D
If each fission reaction in a nuclear reactor emits three neutrons, how many neutrons are produced from three fission reactions? A:one B:three C:six D:nine
D
Which answer choice best explains why atoms of carbon-14 (C-14) are unstable? A:Atoms of C-14 have too many negatively charged electrons and too few positively charged protons. B:Atoms of C-14 have too many positively charged protons and too few negatively charged electrons. C:The attractive force that the protons in the nuclei of C-14 atoms generate is not strong enough to overcome the repulsive force that the neutrons generate. D:The attractive force that the neutrons in the nuclei of C-14 atoms generate is not strong enough to overcome the repulsive force that the protons generate.
D
Which is most likely why many scientists reject the cold fusion theory? A:There is too much waste involved in the process. B:Cold fusion experiments have been conducted at room temperature only. C:The process does not produce enough energy to meet the needs of modern humans. D:The original results have not been replicated consistently and reliably.
D
A large atom decays and emits a particle. After the reaction is complete, the atom's mass has changed substantially. What kind of particle has most likely been emitted? a:alpha particle b:beta particle c:positron d:photon
a
A sample contains 25% parent isotope and 75% daughter isotopes. If the half-life of the parent isotope is 72 years, how old is the sample? a:144 years old b:216 years old c:288 years old d:360 years old
a
A shield of material that reflects neutrons is placed around a radioactive sample. Which change in the nuclear reaction is most likely to happen? a:A chain reaction will be sustained in a subcritical mass. b:The chain reaction in a critical mass will stop. c:A chain reaction will occur at a constant rate in a critical mass. d:The chain reaction in a supercritical mass will slow down.
a
If an unshielded sample of radioactive material emits alpha particles, what effect will it have on a person sitting in the next room? (Assume the wall between rooms is composed of concrete.) a:None, because the wall will block the radiation. b:The radiation will travel through the person's body. c:None, because the radiation will bounce off the person's body. d:The radiation will be totally absorbed by the person's body.
a
Potassium-40 has a half-life of 1.277 mc013-1.jpg 109 years. After 1.022 mc013-2.jpg1010 years, how much potassium-40 will remain from a 500.3-g sample? a:approximately 1.95 g b:approximately 3.91 g c:approximately 62.54 g d:approximately 71.47 g
a
What effect does supercritical mass have on a nuclear reaction? a:The reaction rate increases. b:The reaction produces less energy. c:The reaction involves increased fusion. d:The reaction produces fewer neutrons.
a
Which best describes what forms in nuclear fission? a:two smaller, more stable nuclei b:two larger, less stable nuclei c:one smaller, less stable nucleus d:one larger, more stable nucleus
a
what is a radio isotope
a atom with an unstable nucleus that will go through radioactive decay
what is fission
a heavy nucleus splits in to 2 large fragments to form more stable/smaller nuclei resulting in the relapse of great amounts of energy (radioactive waste is produced) (occurs naturally)
half life and isotopes:
all radio isotopes have a half life half lives are constant for each isotope half lives vary dramatically from isotope to isotope half lives are not affected by temp, pressure, density, or concentration
whats supercritical mass
amount of fissionable material that produces an accelerating rate of fission
whats subcritical mass
amount of fissionable material too small to sustain a constant rate of fission: reaction slows and stops
whats critical mass
amount of fussionable material capable of sustaining a constant rate of fission
what us a parent isotope
an isotope that goes undergoes radioactive decay
These statements describe three different reactions. 1 - An atom shares electrons with another atom. 2 - The nucleus of an atom is split apart. 3 - An atom gains an electron from another atom. Which reaction(s) most likely release the greatest amount of energy? A:1 b:2 c:1 and 3 d:2 and 3
b
What occurs during one half-life? a:Half of a daughter isotope undergoes radioactive decay to form a parent isotope. b:Half of a parent isotope undergoes radioactive decay to form a daughter isotope. c:All of a daughter isotope undergoes radioactive decay to form a parent isotope. d:All of a parent isotope undergoes radioactive decay to form a daughter isotope.
b
Which issue poses the greatest long-term challenge in the development of new nuclear power plants? a:controlling carbon dioxide emissions b:storage of radioactive waste c:controlling fission reactions d:mining of uranium
b
Which statement about the half-life of a radioactive sample is true? a:It is an exact measure of the decay of an individual atom. b:It measures the tendency of a radioisotope to decay radioactively. c:It is affected by the concentration of the radioactive d:substance that is present. It can be calculated based on neutron number.
b
chemical reactions change:
bonding patterns and electron arrangements
when radio isotopes go through radioactive decay it
captures or releases particles to become an isotope of a different element until a stable isotope is formed
difference between a chemical reaction and a nuclear reaction
chemical reaction is interaction between electrons w/ no change in mass nuclear reaction involves splitting of the nucleus and releases more energy than chemical reactions and violates law of conservation of mass
cold fusion controversy
claim that people were able to create energy through fusion at room temp scientific community wasnt able to test studys validity
whats fusion
collision of 2 nuclei ( lighter atomic nuclei combine to form more stable heavier nucleus resulting in a great amount of released energy cant happen on earth
what is alpha decay?
contains 2 neutrons and 2 protons represented by 4/2HE and is least powerful
After a radioactive atom decays, it is the same element that it was before with no measurable change in mass. Which kind of decay has occurred, and how do you know? a:alpha decay because alpha particles have no mass b:beta decay because this kind of decay cannot change one element into another c:alpha decay because it creates a new isotope of the same element d:gamma decay because photons have no mass
d
Which best describes nuclear fusion? a:A nucleus spontaneously splits and absorbs energy. b:Two nuclei spontaneously combine and absorb energy. c:A nucleus collides with a neutron and splits, releasing energy. d:Nuclei combine to form a heavier nucleus, releasing energy.
d
Which procedure will most increase the energy output of a nuclear reactor? a:exposing the core to the outside world b:removing fissile material from the core c:decreasing the amount of steam produced d:raising the control rods out of the reactor
d
what is beta decay
emmission of electron or proton, are stronger than the alpha decay
what is gamma decay
emmission of photon (smallest quantity of light) no charge or mass highest energy (strongest)
whats the law of conservation of energy
energy cant be created or destroyed
both chemical and nuclear reactions involve
energy changes
whats nuclear binding energy
energy needed to split the nucleus of atom in separate proton/neutron
whats cold fusion
fusion reactions that can generate energy csn br carries out at room temp, produces minimal waste most scientists dont think this is possible
what is critical mass
in a chain reaction its the amount of fissionable material capable of sustaining a constant rate of fission
whats a daughter isotope
isotope formed formed from radioactive decay of another isotope knwon as the the parent isotope
whats einsteins law
mass/energy equivilence E=mc2 E= energy m=mass c=speed of light (matter can be converted to energy)
whats the law of conservation of mass
matter cant be created or destroyed
cause of radioactive decay depends on
neutron: proton ratio and the size of nucleus
chemical reactions result in new compounds new elements
new compounds
nuclear reactions result in new compounds new elements
new elements
what are the different energy changes in chemical and nuclear reactions
nuclear: large energy changes chemical: small energy changes
whats radioactive decay
particles from the nucleus of an unstable atom, when its released nucleus becomes more stable c
a mass defect is always positive negative neutral
positive
what is in the middle of the nucleus proton electron neutron
proton and neutron
nuclear reactions change
protons or neutrons
what is a chain reaction
self sustaining fission reaction spread by neutrons that occurs in nuclear reactors and and bombs
how do nuclear reactions react with an isotope
show different behavior, produces different products
how do chemical reactions react with an isotope
shows similar behavior, produces the same chemical compounds
whats half life
time required for half the radiocative nuclei in a sample to decay
