Nuclear fusion — Science definition
The joining of light nuclei into a heavier nucleus, releasing even more energy; it powers the Sun.
Where it is taught
- Nuclear Chemistry — Redox, Cells & Nuclear Chemistry, Physical Science: Chemistry, Grade 11
Questions using nuclear fusion
Problem 1
Explain the difference between nuclear fission and nuclear fusion, and give one real-world example of each.
Answer and explanation
Fission splits a heavy nucleus into lighter ones — for example, uranium-235 splitting inside a nuclear power reactor. Fusion joins light nuclei into a heavier one — for example, hydrogen fusing into helium in the core of the Sun. Both release large amounts of energy.
Problem 2
Explain why nuclear fusion releases energy, and give the most important real-world example of it.
Answer and explanation
In fusion, light nuclei are forced together into a heavier nucleus, and a tiny amount of mass is converted directly into energy according to E = mc², releasing an enormous amount of energy. The most important example is the Sun, where hydrogen nuclei fuse into helium, producing the light and heat that reach Earth.