published by
the Physics Education Technology Project
written by
Trish Loeblein

This lesson plan by an experienced high school physics teacher was created specifically to accompany the PhET simulation "Alpha Decay". It is intended for students who have had prior exposure to half-life and a fundamental understanding of nuclear decay. It provides guided directions to help students make predictions and verify their ideas through data tables and charts. As it progresses, students investigate a specific radioactive decay scenario, using the simulation to compare results of multiple trials. The lesson, as a whole, is designed to encourage deeper thinking about what half-life means in terms of single particles and larger samples.

The alpha decay simulation, which must be open and displayed to complete this activity, is available from PhET at: Alpha Decay.

This lesson is part of PhET (Physics Education Technology Project), a large collection of free interactive simulations for science education.

6-8: 4D/M1a. All matter is made up of atoms, which are far too small to see directly through a microscope.

9-12: 4D/H1. Atoms are made of a positively charged nucleus surrounded by negatively charged electrons. The nucleus is a tiny fraction of the volume of an atom but makes up almost all of its mass. The nucleus is composed of protons and neutrons which have roughly the same mass but differ in that protons are positively charged while neutrons have no electric charge.

9-12: 4D/H3. Although neutrons have little effect on how an atom interacts with other atoms, the number of neutrons does affect the mass and stability of the nucleus. Isotopes of the same element have the same number of protons (and therefore of electrons) but differ in the number of neutrons.

9-12: 4D/H4. The nucleus of radioactive isotopes is unstable and spontaneously decays, emitting particles and/or wavelike radiation. It cannot be predicted exactly when, if ever, an unstable nucleus will decay, but a large group of identical nuclei decay at a predictable rate. This predictability of decay rate allows radioactivity to be used for estimating the age of materials that contain radioactive substances.

11. Common Themes

11B. Models

6-8: 11B/M1. Models are often used to think about processes that happen too slowly, too quickly, or on too small a scale to observe directly. They are also used for processes that are too vast, too complex, or too dangerous to study.

6-8: 11B/M4. Simulations are often useful in modeling events and processes.

11D. Scale

6-8: 11D/M3. Natural phenomena often involve sizes, durations, and speeds that are extremely small or extremely large. These phenomena may be difficult to appreciate because they involve magnitudes far outside human experience.

Common Core State Standards for Mathematics Alignments

High School — Functions (9-12)

Interpreting Functions (9-12)

F-IF.4 For a function that models a relationship between two quantities, interpret key features of graphs and tables in terms of the quantities, and sketch graphs showing key features given a verbal description of the relationship.^{?}

F-IF.5 Relate the domain of a function to its graph and, where applicable, to the quantitative relationship it describes.^{?}

F-IF.6 Calculate and interpret the average rate of change of a function (presented symbolically or as a table) over a specified interval. Estimate the rate of change from a graph.

Linear, Quadratic, and Exponential Models^{?} (9-12)

F-LE.5 Interpret the parameters in a linear or exponential function in terms of a context.

High School — Statistics and Probability^{?} (9-12)

Interpreting Categorical and Quantitative Data (9-12)

S-ID.6.a Fit a function to the data; use functions fitted to data to solve problems in the context of the data.

Making Inferences and Justifying Conclusions (9-12)

S-IC.2 Decide if a specified model is consistent with results from a given data-generating process, e.g., using simulation.

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