Watching elements change through nuclear decay


The elements on Earth today were formed through nuclear reactions, the sole mechanism that has the power to change elements from one kind to another. This lesson involves building a radiation detector called a cloud chamber from every day available materials. This detector will let student see tracks of alpha and beta radiation from radioactive decay right in front of their own eyes! This engaging activity is used as a tool for teaching students: changing elements in balanced nuclear reactions; the properties of alpha and beta-minus radiation; half-lives and the exponential decay law; the decay rate and energy released from radioactive decay and comparing it with fission; and the influence of magnetic fields on charged particles.

Lesson Plan survey link:

The lesson plan covers a wide range of topics and is divided into modules for the teacher to adapt a lesson around. All the details are found in the attached document. The table of content of the document is found below.

Learning Objectives:
• Learn the role of nuclear reactions and how they can change elements to what exists today
• Contrast the properties of alpha and beta-minus radiation to argue for differences in the ionization tracks they should leave
• Observe and describe the behaviors of ionizing radiation ejected when an atomic nucleus decays
• Apply the conservation of the number of protons and neutrons to evaluate the types of elements in the rod are changing to
• Participate in an active “experiment” demonstrating the statistical nature of exponential decay law and half-lives
• Collect, plot and analyze data obtained from this activity to extract the half-life from a decay curve
• Calculate with the half-life the decay rate expected to be observed
• Calculate the energy released by thorium in radioactive decay and compare it with fission reactions in nuclear power plants
• Predict the influence of magnetic fields on charged particles using a mathematical equation
• Relate the laboratory behavior of charged particles in magnetic fields to natural phenomena observed in nature.

Group size: Classroom demonstration led by instructor along with activities for individual students and the entire class to participate in.

Setting: Classroom with flat tables. Ability to make room dark (ideally a room with very few windows that can be blocked). Some larger tables for students to stand around and roll dice on.

Resources needed: Experimental kits (provided), dry ice (requires purchasing on the day), rubbing alcohol (>91% isopropyl), plasticine or playdoh, big cardboard box with duct tape, gloves or a towel, flash lights (the more directional the better), and stands for supporting light.

Table of Contents:
1 Safety Instructions
1.1 Dry Ice
1.2 Rubbing Alcohol (isopropanol)
1.3 Welding Electrode (tungsten with 2% thorium)
2 Lesson Planning (Instructions for teachers)
3 Lesson Description and Activities
3.1 Changing Elements and Nuclear Decay (Base Lesson)
Activity 1: Balancing nuclear decay reaction equations
Activity 2: Tracks of alpha and beta-minus particles in the Cloud Chamber
3.2 Understanding Half-lives
Activity 3: Understanding radioactive exponential decay and half-lives
Activity 4: The decay rate of the Thorium-232 rod
3.3 Comparing radioactive decay with fission and fusion, and the formation of the
elements in the Universe today (Advanced)
Activity 5: Energy being released by the rod
Activity 6: Speed of an alpha particle
Activity 7: Power of a fission reactor
3.4 Influence of magnetic fields on charged particles (not yet completed)
Activity 8: Effects of a magnetic field on alpha or beta-minus particles
4 Relation to research in our low-energy nuclear physics NCSU group
5 Details description and instructions of the Cloud Chamber
5.1 Materials
5.2 Setup and principle of operation
5.3 Step-by-step instruction
5.4 Hints and tips
6 Student Evaluation / Suggested Class Activities
7 Supplementary material