Chapter 25 Review

A uranium atom splits into thorium and helium.

A uranium atom splits into xenon and strontium plus a few neutrons.

A process where one event always triggers one or more additional events.

The minimum amount of mass necessary for one fission to trigger another.

A neutron changes into a proton and an electron.

Two hydrogen atoms combine to make a helium atom.

A nucleon jumps from a high energy level to a lower one and emits a photon.

The amount of time required for 1/2 of the remaining radioactive nuclei to decay.

The strong force between two protons is stronger than the electric repulsion between two protons.

True False

The electromagnetic force extends over a longer distance than the strong nuclear force.

True False

Charge is always conserved in an nuclear process.

True False

Mass changes in nuclear processes.

True False

If two large nuclei were to combine, the process would release energy.

True False

It is possible to predict exactly when a radioactive nucleus will decay.

True False

Which of the following is a legitimate radioactive decay because both charge and mass number are conserved?

198

79

Au →

198

80

Hg +

0

+1

positron +

0

neutrino

60

27

Co →

60

26

Fe +

0

-1

electron +

0

neutrino

212

84

Po →

208

82

Pb +

4

2

He

198

80

Hg +

0

-1

electron →

198

80

Hg +

0

gamma ray

11

6

C →

11

5

B +

1

+1

proton +

0

neutrino

Why is a high temperature required for nuclear fusion to occur?

High temperatures are required to allow the nuclei to have enough kinetic energy to overcome the electromagnetic repulsion and get close enough for the strong force. High temperatures magnify the strong force attraction and allow fusion to occur more readily. High temperatures are required to keep the fusion fuel, deuterium and tritium, stable. High temperatures cause the electromagnetic force to change from a repulsive force to an attractive force which helps the strong force combine the two nuclei.

The purpose of the control rods in a nuclear fission reactor is

to slow down the neutrons, since slower neutrons have a higher probability of causing fission. to absorb neutrons, thus limiting the number of nuclei undergoing fission. to increase the number of neutrons by causing nuclear reactions in the control rods, so that more nuclei in the fuel will undergo fission. to act as spacers to keep the fuel elements apart. to contain material to be transformed into new fissionable fuel by neutron irradiation.

Uranium-238 alpha decays, emitting a helium-4 nucleus. What is the mass number of the product?

230 234 238 242 246

The process known as nuclear fission is primarily responsible for

the energy produced by the sun. the explosion of a hydrogen bomb. the energy produced by a nuclear reactor. electron-positron annihilation. more than one of the above

Both fission and fusion can result in a release of energy. Why?

The strong force is attractive over short distances and repulsive at larger distances. Any change to a nucleus is going to convert mass into energy. The nuclei of atoms near the middle of the periodic table have the least energy and the nucleons with the smallest mass. Either combining large nuclei or splitting small nuclei results in an increase in energy. This energy is released as heat.

When you compare the mass of the products to the mass of the reactants in a fission reaction, what do you find? (note the question is asking about mass, not mass number)

The mass is the same on each side The products have more mass The reactants have more mass

Carbon-14 (¹⁴C) is not stable and it spontaneously decays into nitrogen-14 (¹⁴N) and an electron by a radioactive beta-decay. Which of the following is true about the decay?

Carbon-14 has more entropy than the products. The total charge of the carbon-14 is greater than the total charge of the products. One of the protons in carbon-14 changed into a neutron. The total number of nucleons stays the same. The mass of the nitrogen-14 plus the electron will be greater than the mass of the carbon-14 atom.

From the graphical information presented below, estimate the half-life of the radioactive element whose decay curve is plotted. A graph of radioactive decay.

1 year 1.5 years 2.5 years 5 years

In which of the following nuclear reactions is total charge conserved?

alpha decay beta decay gamma decay electron capture All of the above

Carbon-14 is a radioactive isotope of carbon. Nitrogen-14 is naturally occurring. If you compare the two, what would you expect to find?

A C-14 nucleus has more mass. An N-14 nucleus has more mass. The masses of the two are equal.

Which of the following nuclear reactions has a proton changed into a neutron?

¹⁴C → ¹⁴N + _-1e ²³⁸U → ²³⁴Th + ⁴He ⁴⁰K + _-1e → ⁴⁰Ar ²³⁵U + ¹n → ⁹²Kr + ¹⁴¹Ba + 3¹n

Which of the following is true regarding forces in nuclei?

The electromagnetic force is weaker than the strong force, and therefore has no important effects that need to be taken into account in studying nuclei or nuclear energy. The electromagnetic force, though weaker than the strong force, helps to bind nucleons together into nuclei. The electromagnetic force acts as a disruptive force in large nuclei, creating repulsions which help in fission. The electromagnetic force, although disruptive at long range, is attractive at short range and helps keep small nuclei together. The strong force is short-range, and therefore of no major importance in nuclear energy considerations. The electromagnetic force, on the other hand, is very important in fission and fusion reactions.

Which of the following would be the best fuel for a fission reaction?

Hydrogen Iron Plutonium

Which of the following is the biggest technical problem with using fusion as a source of energy?

The scarcity of fuel (deuterium). The danger of long-lived radioactive wastes. The danger of a runaway reaction. The energy needed to overcome the electromagnetic repulsion of like charges. The scarcity of suitable material for control rods.

An unstable nucleus which has a tendency to spontaneously change its form with the emission of high-energy particles or photons is said to be

ionized. radioactive. an isotope. annihilated. critical.

The process that produces most of the explosive energy of a hydrogen bomb, and that is believed to be responsible for the energy released by the sun, is called

artificial transmutation. nuclear fission. nuclear fusion. radioactivity. electron-positron annihilation.

Isotopes of an element are different atoms of the element that

have the same mass number, but differ in atomic number. have the same number of neutrons, but differ in mass number. have the same number of neutrons, but differ in atomic number. have the same number of protons, but differ in mass number. have the same number of protons, but differ in atomic number.

Nuclear fission is when

a large nucleus breaks apart into smaller pieces protons and neutrons decay into simpler particles electrons combine with protons to form neutrons small nuclei combine to form a larger nucleus

What is the approximate range of the nuclear strong force? (In other words, what is the distance over which the strong force is significant?)

much smaller than the size of a nucleus about the size of a nucleus about the size of an atom indefinite - nuclei feel each other's influence over arbitrary large distances

Chapter 25 Review

Video Review

Key Concept Summary

TA Summary

Vocabulary

True/False

Analysis

Free Response