CBSE Class 10 Science 2019 · Paper 31/3/3 · Question 6

Process: nuclear fission. Explanation: In a nuclear reactor, the nucleus of a heavy atom such as uranium-235 is bombarded with slow (low-energy) neutrons. It splits into two lighter nuclei, releasing more neutrons and a tremendous amount of energy, because the small mass lost, $\Delta m$, is converted into energy ($E=\Delta m{c}^2$). The freed neutrons split more nuclei in a controlled chain reaction, and the heat produces steam that drives turbines to generate electricity. Advantages over fossil fuels (any two): (i) a very small amount of fuel gives an enormous amount of energy - the fission of one uranium atom releases about 10 million times the energy of burning one carbon atom of coal; (ii) it releases no carbon dioxide or smoke, so it gives clean electricity; (iii) the chain reaction is self-sustaining.