Engage: Where does the energy come from?

Time Estimated: 15 minutes Materials: Internet access to Nuclear Processes Simulator, science notebook

Phenomenon: Think about the Sun. It shines brightly every day, providing Earth with light and heat, and it has been doing this for over 4.5 billion years! We also use nuclear power plants on Earth to generate huge amounts of electricity. But how exactly does this work? What changes happen inside the atoms themselves to produce such massive amounts of energy compared to burning coal or wood?

Questions: In your notebook, write down:

1. What do you think happens to the core of an atom (the nucleus) during a “nuclear process”?
2. Why do you think nuclear reactions release so much more energy than chemical reactions (like a campfire)?

Explore: Investigating Nuclear Reactions

Time Estimated: 30 minutes

In this activity, you will use the Nuclear Processes Simulator to observe three different types of nuclear reactions: Alpha Decay, Fission, and Fusion.

Part 1: Alpha Decay

1. Open the simulation and select Alpha Decay.
2. Notice the initial nucleus of Uranium-238 (U-238). Record its number of protons and neutrons.
3. Click Trigger Reaction. Observe what happens to the nucleus.
4. Record the products that are formed: the new larger nucleus (Thorium-234) and the alpha particle (He-4). Note the number of protons and neutrons for each product.
5. Notice the energy wave indicating energy release.

Part 2: Fission

1. Reset the simulation and select Fission.
2. Notice the setup: a neutron is heading towards a Uranium-235 (U-235) nucleus.
3. Click Trigger Reaction. Observe the intermediate step (U-236) and the final products.
4. Record the products: Barium-144 (Ba-144), Krypton-89 (Kr-89), and three neutrons. Note the protons and neutrons.
5. Notice the energy released.

Part 3: Fusion

1. Reset the simulation and select Fusion.
2. Notice the two initial nuclei: Hydrogen-2 (Deuterium, H-2) and Hydrogen-3 (Tritium, H-3).
3. Click Trigger Reaction. Observe the nuclei merging.
4. Record the final products: Helium-4 (He-4) and a neutron. Note the protons and neutrons.
5. Notice the energy released.

Data Table

Explain: Making Sense of the Data

Time Estimated: 20 minutes

Using the data you collected from the simulation, answer the following questions:

1. Conservation of Particles: For each of the three processes, compare the total number of protons before and after the reaction. Do the same for the neutrons. What rule can you establish about the total number of protons and neutrons in nuclear processes?
2. Identifying Processes:
   • Describe what happens to the original nucleus in a fission reaction.
   • Describe what happens to the nuclei in a fusion reaction.
   • Explain how alpha decay is similar to a small-scale fission reaction.
3. Identity Change: In alpha decay, Uranium turns into Thorium. Why does the identity of the element change? (Hint: What defines an element?)

Elaborate/Evaluate: Modeling Nuclear Processes

Time Estimated: 30 minutes

Your Task: Create a visual model or series of diagrams to illustrate the changes that occur during fission, fusion, and alpha decay. Your models must include:

• A clear identification of the elements involved by their number of protons.
• The total number of protons and neutrons before and after the process, demonstrating conservation.
• The identity of any emitted particles (e.g., alpha particles, neutrons).
• A qualitative representation of the massive scale of energy released during these processes compared to a typical chemical reaction (like burning paper).

Checklist:

• Model of Alpha Decay (U-238 -> Th-234 + Alpha)
• Model of Fission (U-235 + n -> Ba-144 + Kr-89 + 3n)
• Model of Fusion (H-2 + H-3 -> He-4 + n)
• Clear labeling of protons and neutrons for all particles.
• Explicit demonstration that total protons + neutrons are conserved.
• Representation of the large energy release.

Extension Options

• Stellar Lifespans: Research the fusion processes that happen in stars. How does the size of a star affect the rate of fusion and its overall lifespan?
• Nuclear Medicine: Investigate how alpha, beta, or gamma decay is used in medical imaging and treatments. Explain how the energy scale of these processes makes them both useful and potentially dangerous.

Teacher Notes

NGSS Alignment

• Performance Expectation: HS-PS1-8: Develop models to illustrate the changes in the composition of the nucleus of the atom and the energy released during the processes of fission, fusion, and radioactive decay.
• Science and Engineering Practice (SEP): Developing and Using Models (Develop a model based on evidence to illustrate the relationships between systems or between components of a system).
• Disciplinary Core Idea (DCI): PS1.C: Nuclear Processes (Nuclear processes, including fusion, fission, and radioactive decays of unstable nuclei, involve release or absorption of energy. The total number of neutrons plus protons does not change in any nuclear process).
• Crosscutting Concept (CCC): Energy and Matter (In nuclear processes, atoms are not conserved, but the total number of protons plus neutrons is conserved).

Evidence Statement Mapping

1. Components of the model: Students will develop models identifying elements by protons, showing protons/neutrons before and after, identifying emitted particles (alpha), and indicating the large scale of energy changes.
2. Relationships: Students’ models will illustrate that the total number of neutrons plus protons is conserved, and that the energy scale is massive compared to chemical processes.
3. Connections: The fusion model will show nuclei merging to form a larger nucleus; the fission model will show a nucleus splitting; and the alpha decay model will show the release of an alpha particle and a change in element identity, acting as a type of fission.