### Nuclear Reaction

- In a nuclear reaction, the mass of the parent particles will become less (know as mass defect). The defected mass is then converted into energy called the nuclear energy.
- In short, nuclear energy is the energy released owing to the defect of mass in a nuclear reaction.
- There are 2 types of nuclear reaction
- nuclear fission
- nuclear fusion
- Nuclear fission is the process of splitting nucleus into 2 smaller nuclei whereas nuclear fusion is the process which 2 small nuclei combine to form a larger nucleus.

### Nuclear Fission

- Nuclear fission is a process involving the splitting of a heavy nucleus into two nuclei of roughly equal mass and shooting out several neutrons at the same time.
- Nuclear fission seldom occurs spontaneously. Usually, it occurs when the heavy nucleus is bombarded by a neutron.
- Fission reaction resulting from neutron absorption is called induced fission. Nuclei that undergo fission without initial neutron absorption are undergoing spontaneous fission.
- Two typical examples of fission reactions:
- $U+n\to Ba+Kr+3n+Energy$
- $U+n\to Xe+Sr+2n+Energy$

**Example 1**

In a nuclear reaction, the mass difference in the reaction is 1.5 x 10

^{-8}kg. Find the heat released in this reaction. [Speed of light = 3.0 x 10

^{8}ms

^{-1}]

**Answer**:

Mass defect, m = 1.5 x 10

^{-8}kg

Heat released,

$$\begin{array}{l}E=m{c}^{2}\\ E=(1.5\times {10}^{-8}){\left(3.0\times {10}^{8}\right)}^{2}\\ E=1.35\times {10}^{9}J\end{array}$$

**Example 2**

A nuclear explosion released 8.2 x 10

^{13}J of energy. What is the mass defect of uranium-235 in this reaction?

[Speed of light = 3.0 x 10

^{8}ms

^{-1}]

Answer

$$\begin{array}{l}E=m{c}^{2}\\ (8.2\times {10}^{13})=m{\left(3.0\times {10}^{8}\right)}^{2}\\ m=\frac{8.2\times {10}^{13}}{{\left(3.0\times {10}^{8}\right)}^{2}}\\ m=9.11\times {10}^{-4}kg=0.911g\end{array}$$