1. Unit 8 Section 2: Nuclear Reactions
An Introduction to Nuclear Fission and Fusion

2. Objectives:
Explain that nuclear reactions deal with interactions between the nuclei of atoms and chemical reactions occur when electrons interact.
Describe the relationship between matter and energy.
Explain and differentiate between nuclear fission and nuclear fusion.
Understand that both fission and fusion processes deal with matter and energy.

3. Nuclear Energy vs. Chemical Energy
What is the difference between nuclear and chemical energy?
Chemical Energy: Energy that is released during chemical reactions. Chemical energy involves electrons.
Nuclear Energy: Energy that is released from the atomic nucleus. This involves much larger energies than chemical reactions.

4. Matter and Energy Recall the law of conservation of energy:
Energy cannot be created or destroyed.
New concept:
Matter and energy are 2 forms of the same thing

5. Einstein’s Famous Equation:E = mc2
Matter can be changed into Energy
Einstein’s formula tell us how the change occurs
In E = mc2,
E = Energy
m = Mass
c = Speed of Light (Universal Constant)

6. E = mc2 The equation can 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
c = 3.0 x 108 m/s

7. Fission: What is it? Fission: Fission fragments(products):
The process of splitting an atomic nucleus into fission fragments.
Fission fragments(products):
In the form of smaller atomic nuclei and neutrons
Releases radiation

8. Fission (cont’d)
LARGE amounts of energy are produced by the fission process
Fission involves heavy atoms with a lot of protons and neutrons (nucleons)
How and why does fission happen?
How: the nuclei of the heavy atoms are hit by neutrons; this starts the fission process.
Why: fission occurs because of the electrostatic repulsion created by large numbers of protons within the nuclei of heavy atoms.

9. Example of Fission Reaction
Start with:
U neutron
Product:
2 neutrons + Kr-92 + Ba Energy

10. Explanation of Fission Reaction
A neutron hits an atom of U-235.
It absorbs the neutron and becomes U-236 which is unstable.
Fission occurs and more neutrons are released in the reaction.
The stray neutrons strike other U-235 atoms to start a nuclear chain reaction.

11. The Fission Process

12. Fission (cont’d) The fission process is NATURAL Why is fission useful?
There was a natural uranium reactor in West Africa over 2 billion years ago.
Why is fission useful?
It generates a large amount of energy and this heat can be captured by nuclear power plants to produce electricity.

13. What elements are good for fission?
Uranium 235 (U-235)
Uranium 238 (U-238)
Elements with an atomic number higher than 92 do not exist in nature; they are also good for the fission process.

14. Fusion: What is it? Fusion:
A nuclear reaction in which two light nuclei combine or fuse to make a larger, heavier nucleus.
This process generates LOTS of energy (Remember E = mc2).
In order for fusion to begin, a large amount of energy is needed to overcome the electrical charges of the nuclei and fuse them together.

15. Fusion Facts
Fusion reactions DO NOT occur naturally on our planet, but nuclear fusion is what powers the stars.
The sun fuses hydrogen atoms to produce helium, subatomic particles, and a large amount of energy.

16. Diagram of Nuclear Fusion

17. Review
Mass and energy are two forms of the same thing; neither can be created or 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 nuclei are combined into a single, heavier atomic nucleus.

18. Quiz Question #1
Which nuclear process produces large amounts of energy?
A. Fission
B. Fusion
C. Both fission and fusion
D. Neither fission or fusion

19. Quiz Question #1
Which nuclear process produces large amounts of energy?
A. Fission
B. Fusion
C. Both fission and fusion
D. Neither fission or fusion

20. Quiz Question #2 Fission is the process that __________ atomic nuclei.
A. combines
B. burns up
C. stores
D. splits

21. Quiz Question #2 Fission is the process that __________ atomic nuclei.
A. combines
B. burns up
C. stores
D. splits

22. Quiz Question #3
Mass may be converted into energy.
A. True
B. False

23. Quiz Question #3
Mass may be converted into energy.
A. True
B. False

24. Quiz Question #4 The fission process requires heavy atomic nuclei.
A. True
B. False

25. Quiz Question #4 The fission process requires heavy atomic nuclei.
A. True
B. False

26. Quiz Question #5
Name the nuclear reaction that occurs within the sun.

27. Quiz Question #5 Name the nuclear reaction that occurs within the sun.
Nuclear Fusion

28. Quiz Question #6
Fission is a natural process that occurs on the planet earth.
A. True
B. False

29. Quiz Question #6
Fission is a natural process that occurs on the planet earth.
A. True
B. False

30. Quiz Question #7
Explain this equation:
E = mc2

31. Quiz Question #7 Explain this equation: E = mc2
Energy is equal to mass times the speed of light squared.