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the Physics Education Technology Project
This student hand-out was created specifically to accompany the PhET simulation "Alpha Decay". Appropriate for grades 8-12, it provides guided directions to help students understand the random nature of decay of a radioactive substance (Polonium-211). As they watch the alpha particle eject from the nucleus, they can see the "parent" decay into an atom with a mass number of 4 less than the original. Reset the nucleus to see the randomness. Next, the ante is upped, as students switch the view to "Multiple Atoms". They can empty a "Bucket" of 100 Polonium-211 atoms and watch a pattern of decay simulated among multiple particles. Even though the decay rate of an individual atom is not predictable, the simulation clearly depicts the trend that half the atoms will decay by the designated half-life.
The alpha decay simulation, which must be open and displayed to perform 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
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.
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
Standards for Mathematical Practice (K-12)
MP.4 Model with mathematics.
High School — Functions (9-12)
Interpreting Functions (9-12)
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.1.c Recognize situations in which a quantity grows or decays by a constant percent rate per unit interval relative to another.
F-LE.5 Interpret the parameters in a linear or exponential function in terms of a context.
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