This is the teacher guide for this lesson. A student-focused guide to assist learners as they perform the activity is available.
View the student guide: Three-legged Challenge for Thermonuclear Fusion
Created by SURA DADI from Noun Project
Teacher Guide
Three-legged Challenge for Thermonuclear Fusion
Discovering a crucial criterion to achieve thermonuclear fusion
What are the three crucial variables that determine the success of a thermonuclear fusion reactor? How do we determine these variables by playing a science game with velcros?
- Brown paper bag (proxy for the volume of a nuclear reactor)
- Velcro strips. Separate. The “hook” strip will represent deuterium and the “loop” strip will represent tritium. When they stick together it will represent fusion.
- Scissors (if using large roll of velcro tape)
- Bulk packing peanuts
- Pen/pencil and paper
- Clock or stopwatch (the one on a cell phone works great!)
Students will use velcro loops and hooks (attached to packing peanuts) as an analogy for nuclear fusion. They will use different experimental protocols to determine the factors needed for nuclear fusion. They can extend their thinking to understand why nuclear fusion for energy production is so difficult to achieve.
- Total time45 - 60 Minutes
- Education levelGrades 6 - 10
- Content AreaStates of Matter: Plasma
- Educational topicmatter, energy, density, temperature, charges, force between charged particles (attraction vs repulsion)
- The Science behind thermonuclear fusion:
a. What is thermonuclear fusion?
We know that all the things we see around us (tables, chairs, white boards, the air we breathe and even ourselves!) are made up of atoms. Inside all atoms, we have a very tiny positively charged part called the “nucleus”. Now, when the nucleus of one atom merges together with another nucleus of another atom, we call that process “nuclear fusion”. It simply comes from the fact that one nucleus “fuses” with another one.
Now, we also realize that the word “thermo” means “related to temperature”. We all know about “thermometers” (measures our body temperature to check if we have a fever) and “thermos flask” or “thermoflask” bottles keeps our coffee hot. In the same line of thought, “thermonuclear fusion” means fusion that happens due to “thermal” effects, meaning that the nuclear fusion happens due to very high temperatures. Sometimes we just call this whole process “fusion”.
b. Why is “fusion” important?
When the nuclei from the atoms of light elements fuse together, they make heavier nuclei and they release a lot of energy. This extra amount of energy that comes out due to fusion can be used as a source of energy to produce electricity to power the world around us. The importance of electricity can be felt when we have a blackout after a storm, for example. Hence, if we can get electricity from fusion, it will be very beneficial to humankind. We note that the sun (and all the stars) is an example where fusion is occurring all the time.
c. Why is fusion difficult to achieve?
You might know that a nucleus has a positive charge, and when we try to bring two positive charges towards each other, they will repel. If nuclei repel each other, how can fusion ever happen? If the nuclei come very, very close to one another, then instead of repelling, they attract each other and get stuck, that is “fuse”. This is because at that very small distance, there is an additional very strong attracting force called the “nuclear force” which can be much stronger than the repulsion force, and we can get fusion. Thus fusion will occur only when the attracting nuclear force is larger than the repelling electrostatic force.
Now, what are the conditions that will increase the chances that two nuclei will fuse? These are the following conditions that will help us:
i. Increase the number of nuclei in a given volume (given by n): The more the number of nuclei, the more the chance that they will bump into each other and fuse. The number of nuclei per unit volume is called “density”.
ii. Increase the temperature of the system (given by T): The hotter the nuclei, the higher is the random motion and the speed of the nuclei, and hence higher is the chance that one nuclei can overcome the repulsion due to the positive charge of another nuclei and get very, very close to another nuclei. We remember that only if they can come very, very close to one another, can they fuse (thanks to the attractive nuclear force)!
iii. Increase the amount of time in which these nuclear reaction are happening (given by t): The longer we can keep all the nuclei together (remember that they are all positively charged, so unless they can come very, very close to one another, in general they would like to repel each other and go out of the system), the higher the chances that they will fuse.
I commonly refer to this as the “three legged challenge”.
Key terms
In this activity, students will go on an exciting journey to explore the amazing world of plasma and its different uses and cool features. Plasma is the fourth state of matter and is a special kind of electrified gas found everywhere in the universe. Even though plasma is very common, people often forget about it. In this activity, students will check out different plasma phenomena and sort them by temperature and density. They will also look for patterns in this state of matter.
Teacher Tips:
- Suggested STEP UP Everyday Actions to incorporate into activity
- When pairing students, try to have male/female partners and invite female students to share their ideas first
- As you put students into groups, consider having female or minority students take the leadership role.
- Take note of female participation. If they seem to be taking direction and following along, elevate their voice by asking them a question about their experiment.
- Consider using white boards so students have time to work through their ideas and brainstorms before saying them out loud.
- As students experiment, roam around the room to listen in on discussion and notice experiment techniques. If needed, stop the class and call over to a certain group that has hit on an important concept.
- Consider culturally responsive tools and strategies and/or open ended reflection questions to help push student thinking, have students track their thinking during the activity, connect to their lives, and create opportunities to develop STEM identity.
- Allow the work of physicists to come alive by signing up for a virtual visit from a working physicist using APS’s Physicist To-Go program. You can request a plasma scientist to talk about the concepts students learned in this activity!
- Atom: the smallest indestructible part of any element. They consist of a positively charged nucleus at the center (the blue spherical marble in the figure below) and negatively charged electrons (the red spherical marble in the figure below) roaming around the nucleus. [Interesting thought: How small is an atom? A very rough imaginary idea would be: If an apple was expanded to be as large as the earth, then the atoms in the apple would be as big as the original apple!]
- Nucleus: The very tiny, positively charged portion of the atom that sits at the very center of the atom. [Interesting thought: Again, how tiny is the nucleus? If an atom has a radius of 1 mile, then the nucleus is only as big as a marble with 1 cm radius! In other words, in the figure of the nucleus above, if the blue ball at the center is a small (1 cm radius) marble, then the radius of the blue lines on which the red electrons are moving would be a mile! The nucleus is that small/tiny!
- Electron: The indivisible, negatively charged part of the atom. Electrons come in units of 1, 2, 3, 4 … and so on and so forth. They cannot be broken into pieces or divided any further.
- Ions: If you take off the negatively charged electron (one or more of them) from an atom, then the remaining positively charged part is called the ion. An ion typically has a nucleus and some electrons (with less negative electrons than that of the positive nucleus, hence ions have a net positive charge). [Interesting thought => If you take out all the electrons of an atom, the ion is nothing else but the nucleus of that atom!]
- Plasma: electrically charged gas, where the negatively charged electrons and the positively charged ions can move freely. We typically start with a gas, give it a lot of energy to knock out an electron from an atom, and then we will have freely moving electrons and ions => plasma!
- Hydrogen: Lightest element in our universe consisting of one proton and one electron
- Deuterium: Heavier form of hydrogen with the nucleus being twice as heavy because it includes a neutron along with a proton in the nucleus.
- Tritium: Another even heavier form of hydrogen, with the nucleus being three times as heavy because it includes one proton and two neutrons.
Objectives
*Students will do experiments with velcros (used as a proxy for a nucleus) to determine the variables that lead to more of them sticking to each other as a model for thermonuclear fusion
*It is important to understand that student goals may be different and unique from the lesson goals. We recommend leaving room for students to set their own goals for each activity. Have students share their questions or objectives using an Essential Question board or something similar.
Before the experiment
Setting up
Split the packing peanuts in half.
One one half, attach the “hook” part of the velcro strip around the top of each peanut. These will represent Deuterium.
Take the other half of the peanuts and attach the “loop” part of the velcro strip to the top of each peanut. These will represent the Tritium
During the experiment
Collecting data
Make sure students are put into intentional groups. See Teachers Tips above.
Students will complete the experiment using the Student Guide where we have outlined the experiment for students and along the way, they record results and answer questions.
With all experiments, think about asking students to predict the outcomes before they experiment. Consider adding a predication column to the table.
CONCLUSION to Experiment 1: The fusion yield (locked velcros, in this game, which is similar to fused He nuclei in an actual He reactor) is proportional to the number of hooks (D nuclei) and loops (T nuclei) in the box. Since the box has a fixed volume, the number of nuclei divided by the volume gives us density. Hence we can deduce from this part of the experiment that when everything else is kept constant, fusion yield is proportional to density (N).
CONCLUSION to Experiment 2: The fusion yield (locked velcros, in this game, which is similar to fused He nuclei in an actual He reactor) is proportional to how vigorously the particles inside the box are moving. Now, the energy in a system due to its motion is called kinetic energy and the temperature of a system is an effective measure of this kinetic energy. Hence we can deduce from this part of the experiment that fusion yield is proportional to temperature (T).
CONCLUSION to Experiment 3: The fusion yield (locked velcros, in this game, which is similar to fused He nuclei in an actual He reactor) is proportional to how long you are doing the experiment for, which is simply the time for how long your nuclear reactor is ON. Hence we can deduce from this part of the experiment that fusion yield is proportional to the amount of time (t) of the experiment being done.
Analyzing data
Continue to listen in on each group’s discussion, answer as few questions as possible. Even if a group is off a little, they will have a chance to work out these stuck points later.
Conclusion
Use a Gallery Walk protocol as students answer questions in their Student Guide Conclusion section.
Have them think about what they like and would change as they travel around the gallery.
Have them use sticky notes to capture their thinking and share with the other groups.
Extension: Have students review this resource sheet on modern developments in nuclear fusion:
Nuclear Fusion Resource Sheet AM
Real world connections
- Plasma Career Matching Tool - This tool can be used for any level. It matches students to relevant fusion energy/plasma scientists’ profiles based on their interests and values. They can then research, create their own profiles, and discuss with the class. Encourage your students to take this interactive Career Matching Survey to see what fusion energy/plasma science careers fit them best.
Suggestions for drawing, illustrating, presenting content in creative ways
- Have students read about this art piece that has been incorporated into a nuclear fusion reactor (ITER | Saint-Paul-Les-Durance — Artist | Christine Corday, The Art Hidden In The World’s Largest Nuclear Fusion Reactor)
- Task students with designing an art piece to represent the possibilities of nuclear fusion. Have them write and draw a proposal for their art piece.
Engineering and design challenges connected to the content
- Have students review this resource sheet on modern developments in nuclear fusion: Nuclear Fusion Resource Sheet_AM
- if engineering challenges have a time constraint, students are allowed to keep iterating and developing their ideas outside of class time and continue to participate in the challenge at a later date
**Real world situations/connections can be used as is, or changed to better fit a student’s own community and cultural context.
Step Up Women in Physics
STEP UP Women in Physics lesson: introduces the underrepresentation of women in physics and the role of implicit bias and cultural stereotypes. Helps students examine the conditions for women in physics and discuss gender issues, gendered professions, and personal experience to neutralize the effect of stereotypes and bias.
- MS-PS1-1Develop models to describe the atomic composition of simple molecules and extended structures.
- MS-PS1-2Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
- MS-PS1-4Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
- Science and Engineering Practices (SEPs)Developing and Using Models ▪ Analyzing and Interpreting Data ▪ Constructing Explanations and Designing Solutions ▪ Obtaining, Evaluating, and Communicating Information
- Cross Cutting Concepts (CCCs)Cause and Effect Energy and Matter Scale, Proportionality, and Quantity Systems and System Models Stability and Change
Credits
Created by Dr. Saikat Chakraborty Thakur, Auburn University along with Nicole Schrode, MEd, and Claudia Fracchiolla, PhD, of APS Public Engagement
Reviewed by Kimberly Becker, Avery Jackson, Tiffany O’Dell, Joel Richardson, Allison Scherrer
Extensions by Amanda Maeglin
PhysicsQuest © 2024 by American Physical Society is licensed under CC BY-NC 4.0
License
- Attribution — You must give appropriate credit , provide a link to the license, and indicate if changes were made . You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
- NonCommercial — You may not use the material for commercial purposes