Nuclear Fission and Fusion

Identify whether nuclei are heavy or light. For fission, describe splitting, emitted neutrons, and possible chain reaction. For fusion, describe combination of light nuclei and need for high temperature. Use binding energy per nucleon to explain energy release. For numericals, calculate mass difference and convert to MeV.

A comparison diagram may show a heavy nucleus splitting into two fragments and neutrons for fission, and two light nuclei combining for fusion. If linked to the binding energy graph, mark heavy nuclei moving left toward higher binding energy per nucleon and light nuclei moving right toward higher binding energy per nucleon.

A common wrong answer is that fusion occurs easily at room temperature because it releases energy. Fusion needs extremely high temperature because positively charged nuclei must come close enough for nuclear force to act.

Nuclear fission is the splitting of a heavy nucleus into two medium-mass nuclei with release of energy and usually neutrons. Nuclear fusion is the combination of light nuclei to form a heavier nucleus with release of energy under extremely high temperature and pressure conditions.

Nuclear fission is the splitting of a heavy nucleus into two medium-mass nuclei with release of energy and usually neutrons. Nuclear fusion is the combination of light nuclei to form a heavier nucleus with release of energy under extremely high temperature and pressure conditions. Energy released Q = (mass of reactants - mass of products)c^2 when the product mass is smaller. In nuclear units, Q in MeV = mass difference in u x 931.5. Fission is favoured for very heavy nuclei, while fusion is favoured for light nuclei because both can move products toward higher binding energy per nucleon. In a fission chain reaction, one neutron absorbed by uranium-235 can produce fission fragments, energy, and additional neutrons. In the Sun, fusion of light nuclei is responsible for the large energy output.

Energy is released in both processes because the products have greater binding energy per nucleon than the reactants. In fission, a heavy nucleus such as uranium-235 may absorb a neutron and split into fragments, releasing more neutrons that can continue a chain reaction. In fusion, light nuclei such as hydrogen isotopes combine, but high temperature is needed to overcome electrostatic repulsion between positively charged nuclei. The binding energy curve explains both processes as movement toward more stable nuclei near the peak region. Energy released Q = (mass of reactants - mass of products)c^2 when the product mass is smaller. In nuclear units, Q in MeV = mass difference in u x 931.5. Fission is favoured for very heavy nuclei, while fusion is favoured for light nuclei because both can move products toward higher binding energy per nucleon. If a nuclear reaction has total reactant mass 235.124 u and total product mass 234.904 u, mass difference = 0.220 u. Energy released = 0.220 x 931.5 MeV = 204.93 MeV. Since product mass is smaller, the reaction releases about 205 MeV of energy. This concept is asked through comparison tables, binding-energy curve reasoning, chain reaction explanation, and mass-energy numericals for energy released. A common wrong answer is that fusion occurs easily at room temperature because it releases energy. Fusion needs extremely high temperature because positively charged nuclei must come close enough for nuclear force to act.