Mass Defect Basics Physics Quiz: Understand Nuclear Mass

Grade 10th

Reviewed by Ekaterina Yukhnovich

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By Thames

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| Questions: 20 | Updated: Mar 11, 2026

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1. If the sum of separate nucleon masses is larger than the nucleus mass, the difference is the .

That’s the definition. It is specifically the 'sum of parts' mass minus the 'bound nucleus' mass.

Explanation

That’s the definition. It is specifically the 'sum of parts' mass minus the 'bound nucleus' mass.

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About This Quiz

Mass Defect Basics Physics Quiz: Understand Nuclear Mass - Quiz

This assessment delves into the fundamentals of mass defect in nuclear physics. It evaluates your understanding of nuclear mass, binding energy, and the relationship between mass and energy. By mastering these concepts, learners can gain insights into nuclear stability and reactions, making this knowledge essential for students and enthusiasts of... see morephysics. see less

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2. Mass defect is mainly a sign that:

Nuclei lose matter over time

Binding a nucleus changes the system’s mass because mass and energy are equivalent

Protons are unstable in all atoms

Chemical bonds are stronger than nuclear bonds

It shows mass–energy equivalence in nuclei. When nucleons bind, energy changes, and that energy change is reflected as a measurable mass difference.

Explanation

It shows mass–energy equivalence in nuclei. When nucleons bind, energy changes, and that energy change is reflected as a measurable mass difference.

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3. The mass defect is typically a tiny fraction of the nucleus’s total mass.

True

False

The relative change is small but meaningful. Even a tiny fraction of mass corresponds to a large amount of energy because of c².

Explanation

The relative change is small but meaningful. Even a tiny fraction of mass corresponds to a large amount of energy because of c².

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4. The 'missing mass' in mass defect is best thought of as converted into:

Electrons

Energy (binding energy)

Water

Heat only

It corresponds to energy. That energy may appear as radiation or kinetic energy when the nucleus forms, and it is the same energy you would need to supply to fully separate the nucleus.

Explanation

It corresponds to energy. That energy may appear as radiation or kinetic energy when the nucleus forms, and it is the same energy you would need to supply to fully separate the nucleus.

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5. Why is mass defect not a violation of conservation laws?

Laws don’t apply in nuclei

Total mass–energy is conserved; energy released accounts for the difference

Conservation is only for chemistry

Because mass is imaginary

Mass–energy conservation holds. The 'missing mass' is not lost; it has been converted into energy that left the system during formation (or is stored as binding energy).

Explanation

Mass–energy conservation holds. The 'missing mass' is not lost; it has been converted into energy that left the system during formation (or is stored as binding energy).

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6. A more tightly bound nucleus generally has a larger binding energy, which often means a larger mass defect.

True

False

More binding energy corresponds to a larger energy (and mass) difference. If more energy is released (or would be required to separate the nucleus), the associated mass defect is typically larger.

Explanation

More binding energy corresponds to a larger energy (and mass) difference. If more energy is released (or would be required to separate the nucleus), the associated mass defect is typically larger.

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7. Mass defect is connected to:

Binding energy

Mass–energy equivalence

Nuclear stability trends

Refraction of light

A–C are linked; refraction is unrelated. Mass defect is tied to how strongly nuclei are bound and helps explain energy scales and stability, not optical effects.

Explanation

A–C are linked; refraction is unrelated. Mass defect is tied to how strongly nuclei are bound and helps explain energy scales and stability, not optical effects.

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8. Which statement is correct?

All nuclei have zero mass defect

Most bound nuclei have nonzero mass defect

Mass defect only happens in gases

Mass defect only happens in chemistry

Binding lowers mass relative to free nucleons. Any nucleus with binding energy will show a mass defect because the bound state has lower energy (and thus lower mass) than separated nucleons.

Explanation

Binding lowers mass relative to free nucleons. Any nucleus with binding energy will show a mass defect because the bound state has lower energy (and thus lower mass) than separated nucleons.

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9. Mass defect is measured in units of mass (like kg or atomic mass units).

True

False

It is a mass difference. You can express it in kg (SI) or in atomic mass units (u), depending on what’s most convenient.

Explanation

It is a mass difference. You can express it in kg (SI) or in atomic mass units (u), depending on what’s most convenient.

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10. Mass defect is evidence that:

Energy is not conserved

Mass and energy are linked

Electrons control the nucleus

Light has no energy

It demonstrates mass–energy equivalence. The fact that binding energy shows up as a mass difference is direct evidence that mass and energy are connected.

Explanation

It demonstrates mass–energy equivalence. The fact that binding energy shows up as a mass difference is direct evidence that mass and energy are connected.

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11. “Mass defect” refers to the fact that:

Mass is lost to the air

A nucleus has slightly less mass than the total mass of its separated protons and neutrons

Electrons lose mass when they move

Mass is not conserved

The bound nucleus has lower mass than the sum of free nucleons. This happens because forming a bound system releases energy, and lower total energy corresponds to slightly lower mass.

Explanation

The bound nucleus has lower mass than the sum of free nucleons. This happens because forming a bound system releases energy, and lower total energy corresponds to slightly lower mass.

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12. In the context of nuclei, 'defect' means:

A mistake

A broken nucleus

A difference between two mass values

Radioactive decay

It’s the difference between the sum of free nucleons and nucleus mass. It does not mean something is wrong; it’s just a measured difference that reflects binding energy.

Explanation

It’s the difference between the sum of free nucleons and nucleus mass. It does not mean something is wrong; it’s just a measured difference that reflects binding energy.

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13. Mass defect can be used to calculate binding energy.

True

False

E=Δmc². Once you know the mass defect, converting it with e=mc² gives the binding energy associated with forming the nucleus.

Explanation

E=Δmc². Once you know the mass defect, converting it with e=mc² gives the binding energy associated with forming the nucleus.

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14. Mass defect is most directly related to:

Chemical bonding

Nuclear binding energy

Temperature

Sound

It’s a nuclear effect, not chemical. Mass defect quantifies how much mass corresponds to the binding energy that holds the nucleus together.

Explanation

It’s a nuclear effect, not chemical. Mass defect quantifies how much mass corresponds to the binding energy that holds the nucleus together.

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15. Which is the best interpretation of mass defect?

The nucleus is missing particles

Some energy was released when the nucleus formed, so the bound system has less mass

Protons evaporate

Gravity removes mass

Lower energy bound state corresponds to lower mass. The nucleus isn’t missing matter; it has released energy during formation, and that released energy accounts for the mass difference.

Explanation

Lower energy bound state corresponds to lower mass. The nucleus isn’t missing matter; it has released energy during formation, and that released energy accounts for the mass difference.

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16. Mass defect is typically very small, but it corresponds to a large amount of energy.

True

False

Because c² is huge. Multiplying a tiny m by c² converts it into a significant energy value on nuclear scales.

Explanation

Because c² is huge. Multiplying a tiny m by c² converts it into a significant energy value on nuclear scales.

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17. Mass defect occurs mainly because when nucleons bind, the system’s total energy becomes:

Higher

Lower

Zero

Infinite

Bound states have lower energy; the difference corresponds to binding energy. Since energy contributes to mass, lowering the energy lowers the mass of the bound nucleus compared to free nucleons.

Explanation

Bound states have lower energy; the difference corresponds to binding energy. Since energy contributes to mass, lowering the energy lowers the mass of the bound nucleus compared to free nucleons.

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18. The speed of light is represented by the symbol ______ in e=mc^2.

C is the speed of light. It appears squared in the formula, which is why even tiny mass differences correspond to big energies.

Explanation

C is the speed of light. It appears squared in the formula, which is why even tiny mass differences correspond to big energies.

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19. The equation that links mass and energy is:

F=ma

V=ir

E=mc^2

P=iv

Mass–energy equivalence says mass and energy are interchangeable in a precise way. In nuclear processes, small mass differences can represent large energy changes because of the factor c².

Explanation

Mass–energy equivalence says mass and energy are interchangeable in a precise way. In nuclear processes, small mass differences can represent large energy changes because of the factor c².

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20. Mass defect is connected to nuclear binding energy.

True

False

Binding energy corresponds to an energy difference linked to a mass difference. The mass defect is the 'mass equivalent' of that binding energy through mass–energy equivalence.

Explanation

Binding energy corresponds to an energy difference linked to a mass difference. The mass defect is the 'mass equivalent' of that binding energy through mass–energy equivalence.

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