Nuclear Reactions:

2. Nuclear reactions deal with interactions between the nuclei of atoms The focus of this presentation are the processes of nuclear fission and nuclear fusion Both fission and fusion processes deal with matter and energy

3. Matter and Energy Previous studies have taught us that “matter and energy cannot be created nor destroyed” We now need to understand that Matter and Energy are two forms of the same thing

4. Matter can be changed into Energy Einstein’s formula above tells us how the change occurs In the equation above: E = Energy m = Mass c = Speed of Light (Universal Constant) E = mc2

5. E = mc2 The equation may be read as follows: Energy (E) is equal to Mass (m) multiplied by the Speed of Light (c) squared This tells us that a small amount of mass can be converted into a very large amount of energy because the speed of light (c) is an extremely large number

6. Fission Fission may be defined as the process of splitting an atomic nucleus into fission fragments The fission fragments are generally in the form of smaller atomic nuclei and neutrons Large amounts of energy are produced by the fission process

7. Fission Fissile nuclei are generally heavy atoms with large numbers of nucleons The nuclei of such heavy atoms are struck by neutrons initiating the fission process Fission occurs due to electrostatic repulsion created by large numbers of protons within the nuclei of heavy atoms

8. A classic example of a fission reaction is that of U-235: U-235 + 1 Neutron 2 Neutrons + Kr-92 + Ba-142 + Energy In this example, a stray neutron strikes an atom of U-235. It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission. Notice that more neutrons are released in the reaction. These neutrons can strike other U-235 atoms to initiate their fission.

9. Fission The fission process is an a natural one as a French researcher found a natural uranium reactor in Gabon, West Africa; it has been estimated to be over 2 billion years old Fission produces large amounts of heat energy and it is this heat that is captured by nuclear power plants to produce electricity

10. Fusion is a nuclear reaction whereby two light atomic nuclei fuse or combine to form a single larger, heavier nucleus The fusion process generates tremendous amounts of energy; refer back to Einstein’s equation For fusion to occur, a large amount of energy is needed to overcome the electrical charges of the nuclei and fuse them together

11. Fusion Fusion reactions do not occur naturally on our planet but are the principal type of reaction found in stars The large masses, densities, and high temperatures of stars provide the initial energies needed to fuel fusion reactions The sun fuses hydrogen atoms to produce helium, subatomic particles, and vast amounts of energy

12. Mass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc2) Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nuclei Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus

13. Quiz Which nuclear process produces large amounts of energy? A. Fission B. Fusion C. Both fission & fusion D. Neither fission nor fusion

14. Quiz Fission is the process that _________ atomic nuclei. A. Combines B. Burns up C. Stores D. Splits

15. Quiz Mass may be converted into energy. A. True B. False

16. Quiz The fission process requires heavy atomic nuclei. A. True B. False

17. Quiz Name a nuclear reaction that occurs within the sun:

18. Quiz Fission is a natural process that occurs on the planet Earth. A. True B. False

19. Quiz Explain this equation: E = mc2