When calculating the energy change of a nuclear reaction using mass difference, what does a negative deltaE indicate?

When calculating the energy change of a nuclear reaction using mass difference, what does a negative deltaE indicate?

• A. Energy released.
• B. Energy absorbed.
• C. No energy change.
• D. Energy converted to mass.

Answer: (A)

The energy change in a nuclear reaction is tied to the mass difference through E = Δm c^2, with the sign set by how you define ΔE. If you take ΔE as the final energy minus the initial energy, a smaller final energy means ΔE is negative. In many nuclear processes the products are lighter than the reactants, so mass is lost (a positive mass defect), and that lost mass becomes energy. Therefore the final state has less energy than the initial state, producing a negative ΔE, which corresponds to energy being released as kinetic energy of the products or radiation. If instead the products were heavier, ΔE would be positive and the system would absorb energy. If masses are equal, ΔE would be zero and there’s no energy change.

The energy change in a nuclear reaction is tied to the mass difference through E = Δm c^2, with the sign set by how you define ΔE. If you take ΔE as the final energy minus the initial energy, a smaller final energy means ΔE is negative. In many nuclear processes the products are lighter than the reactants, so mass is lost (a positive mass defect), and that lost mass becomes energy. Therefore the final state has less energy than the initial state, producing a negative ΔE, which corresponds to energy being released as kinetic energy of the products or radiation. If instead the products were heavier, ΔE would be positive and the system would absorb energy. If masses are equal, ΔE would be zero and there’s no energy change.