Fission: conserve charge and nucleons, account for energy
導入済み| English | 意味 |
|---|---|
| chain reaction/tʃeɪn rɪˈækʃn/ | 鎖反応 |
| fission/ˈfɪʃn/ | 核分裂 |
What would explain this observation?
- A neutron can trigger a heavy nucleus to split, releasing energy and further neutrons. Whether the process becomes a chain reaction 链式反应 depends on what happens to those neutrons.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- In nuclear fission 核裂变 a heavy nucleus splits into lighter nuclei. Proton number and nucleon number balance in a nuclear equation. The total rest mass can decrease; the difference corresponds to released energy through E = Δmc².
- fission: Splitting of a heavy nucleus into lighter nuclei; chain reaction: A sequence in which products initiate further events.
What permits a continuing fission chain reaction?
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
Each fission releases two or three neutrons, and if at least one triggers another fission the reaction sustains itself. Escaped neutrons break the chain, and charge conservation is never suspended.
Match each technical term to its precise meaning.
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Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Separate conservation of nucleon number from conservation of total energy. Released neutrons may initiate further fissions, escape or be absorbed. A controlled reactor and an uncontrolled chain reaction have different neutron-management conditions.
- Balance a supplied nuclear equation, use the specified mass data and identify the system. Analyse models or published reactor data; this is not a school attempt to produce fission or handle reactor materials.
Which two habits make the investigation or model in this case more defensible?
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: U-235 absorbs one neutron, forming Ba-141, Kr-92 and three neutrons. Nucleon balance: 235+1 = 141+92+3 = 236. Proton balance: 92 = 56+36. A mass decrease of 2.0×10⁻²⁸ kg corresponds to 1.8×10⁻¹¹ J using c=3.0×10⁸ m/s.
A U-235 nucleus plus one neutron produces fragments with mass numbers 141 and 92. How many neutrons balance the equation? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A U-235 nucleus plus one neutron produces fragments with mass numbers 141 and 92. How many neutrons balance the equation?
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
The result is 3 neutrons. Known: U-235 plus one neutron gives fragments 141 and 92. Nucleon balance: 235 + 1 = 141 + 92 + n, so n = 236 - 233 = 3 neutrons. Proton numbers must balance separately (92 = 56 + 36 for barium and krypton).
Check the conclusion and its limits
- Mass number is not a precise mass in kilograms. Balanced integer labels alone do not calculate the released energy. Radioactive decay and neutron-induced fission are not interchangeable descriptions.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
A balanced nucleon-number equation alone gives the energy release in joules. This claim is false: Integer mass and charge labels only check conservation; they say nothing about energy. The released energy comes from the small decrease in actual MASS via E = mc^2, which needs measured masses, not mass numbers.
Fission: conserve charge and nucleons, account for energy: Separate conservation of nucleon number from conservation of total energy. Released neutrons may initiate further fissions, escape or be absorbed. A controlled reactor and an uncontrolled chain reaction have different neutron-management conditions.
A balanced nucleon-number equation alone gives the energy release in joules.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
Integer mass and charge labels only check conservation; they say nothing about energy. The released energy comes from the small decrease in actual MASS via E = mc^2, which needs measured masses, not mass numbers.
Splitting of a heavy nucleus into lighter nuclei: write the technical term.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
fission means Splitting of a heavy nucleus into lighter nuclei.