a) What is meant by the term "nuclear fission"? [1] b) Write the equation for the nuclear fission of uranium 235. [2] c) What are the uses of nuclear fission? [2]

^{235}_{92}U+^{1}_{0}nslow neutron^{141}_{56}Ba+^{92}_{36}Kr+33^{1}_{0}n

a) Meaning of Nuclear Fission

Nuclear fission is a nuclear reaction in which the nucleus of a heavy atom (like uranium or plutonium) splits into two smaller nuclei when bombarded with a slow-moving neutron. This process releases a large amount of energy and additional neutrons, which can trigger further fission reactions in other nuclei, creating a chain reaction.

^{235}_{92}Uslow neutron^{141}_{56}Ba+^{92}_{36}Kr+33^{1}_{0}n

b) Equation for Nuclear Fission of Uranium-235

The nuclear fission of uranium-235 can be represented as follows:

$${}_{}^{}{}_{92}^{235}\mathrm{U}+{}_{}^{}{}_0^1\mathrm{n}\to {}_{}^{}{}_{56}^{141}\mathrm{Ba}+{}_{}^{}{}_{36}^{92}\mathrm{Kr}+3{}_0^1\mathrm{n}+\text{Energy}$$

• Explanation:
  • A slow neutron (${}_0^{1}n$) strikes a uranium-235 nucleus (${}_{92}^{235}U$).
  • The uranium nucleus splits into barium-141 (${}_{56}^{141}Ba$) and krypton-92 (${}_{36}^{92}Kr$).
  • Three additional neutrons are released, along with a massive amount of energy.

c) Uses of Nuclear Fission

Nuclear fission has several important applications:

1. Electricity Generation

   • Nuclear power plants use controlled fission reactions to produce heat, which converts water into steam.
   • The steam drives turbines connected to generators, producing clean and efficient electricity.

2. Weapons (Nuclear Bombs)

   • Uncontrolled fission reactions release enormous energy in a short time, used in atomic bombs (e.g., Hiroshima and Nagasaki).

3. Medical Applications

   • Radioisotopes produced from fission are used in cancer treatment (radiotherapy) and diagnostic imaging (PET scans).

4. Space Exploration

   • Nuclear reactors provide power for spacecraft and satellites, especially in deep-space missions where solar energy is insufficient.

5. Scientific Research

   • Fission reactions help study nuclear physics, materials science, and develop new technologies.

6. Nuclear Propulsion

   • Ships and submarines use nuclear reactors for long-duration, high-power propulsion without refueling.

---

Note: The energy released in fission is due to the mass defect (Einstein’s equation $E=m{c}^2$), where a small amount of mass is converted into energy.