Questions about Conservation of Mass and Energy in Nuclear Reactions
Conservation of Mass and Energy in Nuclear Reactions
Multiple Choice Questions
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1. What law is primarily applied to nuclear reactions involving mass and energy?
A) Newton’s Third Law
B) Law of Definite Proportions
C) Law of Conservation of Mass-Energy
D) Law of Constant Composition
E) Ohm’s Law
2. Who proposed the mass-energy equivalence principle E=mc2E = mc^2E=mc2?
A) Isaac Newton
B) Marie Curie
C) Albert Einstein
D) Niels Bohr
E) Max Planck
3. In nuclear reactions, a small amount of mass is converted into:
A) Light
B) Sound
C) Energy
D) Particles
E) Heat only
4. What is the result of mass defect in nuclear fission?
A) Loss of atoms
B) Decrease in gravity
C) Release of energy
D) Increase in mass
E) Decrease in temperature
5. What does the "c" represent in the equation E=mc2E = mc^2E=mc2?
A) Mass
B) Charge
C) Speed of sound
D) Speed of light
E) Capacitance
6. Which of the following is true about total energy and mass in a closed nuclear reaction?
A) Mass is lost forever
B) Energy increases indefinitely
C) Total mass and energy remain constant
D) Only kinetic energy is conserved
E) Both mass and energy increase
7. The mass of a nucleus is _____ than the sum of the individual nucleons.
A) Greater
B) Equal
C) Less
D) Same
E) Variable
8. The missing mass in a nucleus is known as the:
A) Isotope gap
B) Quantum void
C) Mass defect
D) Atomic decay
E) Fusion lag
9. What is the primary source of energy in nuclear power plants?
A) Combustion
B) Fission and mass-energy conversion
C) Magnetic force
D) Friction
E) Photosynthesis
10. In nuclear fusion, energy is released due to:
A) Absorption of photons
B) Mass gain
C) Mass-to-energy conversion
D) Splitting of atoms
E) Loss of electrons
11. Which nuclear process powers the sun?
A) Fission
B) Alpha decay
C) Beta decay
D) Gamma emission
E) Fusion
12. A nuclear reaction conserves which of the following?
A) Mass only
B) Energy only
C) Mass and energy combined
D) Volume
E) Color
13. Which unit is commonly used to express energy in nuclear reactions?
A) Watt
B) Joule
C) Calorie
D) Electronvolt (eV)
E) Mole
14. Why does nuclear fusion release energy?
A) Mass increases
B) Electrons collide
C) Mass of products is less than mass of reactants
D) Magnetic fields align
E) Neutrons absorb energy
15. How does the conservation of mass-energy apply in beta decay?
A) Mass disappears
B) Mass is unchanged
C) Some mass is converted into kinetic and radiation energy
D) New atoms are created
E) Electrons gain mass
16. Why is mass considered a form of energy in nuclear physics?
A) Mass can conduct electricity
B) Mass causes chemical reactions
C) It can be transformed into energy
D) It radiates photons
E) It resists gravity
17. What explains the energy released in both fission and fusion?
A) Increase in particle charge
B) Increase in nuclear size
C) Mass defect and E=mc2E = mc^2E=mc2
D) Decrease in kinetic energy
E) Heat gain
18. During radioactive decay, what happens to mass and energy?
A) Both are lost
B) Both are gained
C) Both are conserved
D) Energy is lost, mass is gained
E) Neither is involved
19. A small loss of mass in a nuclear reaction is converted into a:
A) Decrease in temperature
B) Gain in atom count
C) Significant amount of energy
D) Weak magnetic field
E) Negative charge
20. Which of the following reactions best illustrates mass-energy conversion?
A) Neutralization
B) Photosynthesis
C) Fission of uranium-235
D) Dissolving salt
E) Boiling water
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Answer Key with Explanations
1. C – The law of conservation of mass-energy states that the total of both remains constant in a closed system.
2. C – Einstein introduced E=mc2E = mc^2E=mc2, showing that mass and energy are interchangeable.
3. C – In nuclear reactions, some mass is converted to energy.
4. C – Mass defect leads to energy release in fission.
5. D – “c” is the speed of light in a vacuum (~3.0 × 10⁸ m/s).
6. C – Total mass and energy are conserved; they can convert into each other.
7. C – The actual nuclear mass is less due to mass defect.
8. C – Mass defect refers to the "missing mass" that appears as energy.
9. B – Nuclear power uses fission, where mass is converted into energy.
10. C – Fusion releases energy when mass is transformed into energy.
11. E – The sun uses nuclear fusion, mainly of hydrogen atoms.
12. C – Mass and energy together are conserved in nuclear reactions.
13. D – Energy in nuclear physics is often measured in electronvolts (eV).
14. C – Fusion creates products with less mass than the reactants.
15. C – The mass difference appears as energy in beta decay.
16. C – Mass is energy in another form, per Einstein’s equation.
17. C – The mass defect is the key source of energy in fission and fusion.
18. C – Mass and energy are both conserved; some mass becomes energy.
19. C – Even a tiny mass can yield significant energy due to E=mc2E = mc^2E=mc2.
20. C – Fission of uranium-235 is a clear example of mass converting into energy.
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