Half-Life Activity With Practice Problems

Half-Life is a difficult concept for students to grasp. This activity is a hands-on, two-part activity that takes the students through some examples using construction paper for Part A, and Part B uses either pennies or similar items as radioactive particles.

A background sheet is included which explains the concept of half-life. Use it as a class set for reading, or give each student a copy for their notebook.

Part A uses a construction paper circle to represent 100% of a radioactive substance, and then leads students through steps to show them how each time it is cut in half, the radioactive amount is reduced to 1/2, 1/4, 1/8, etc. Students are asked questions about their findings and answer half-life problems based on their new knowledge. I find this activity to be the most effective in reinforcing the concept of half-life.

Part B approaches half-life differently, by using small items such as pennies which are poured onto a piece of paper. The 'radioactive atoms' are counted and the stable atoms are removed. Only the 'radioactive atoms' are returned to the box. The pennies are shaken and poured out again, and students separate the radioactive particles from the stable ones. The process is repeated until all radioactive particles are gone. The students record their data in the given data table, and graph their data on the given graph. Practice problems are given which are more difficult than those found in Part A. This activity shows students that even though a substances half-life may be short, it still takes a long time for all of the radioactive nuclei to decay.

Use either activity alone if desired.

I use this set after the students are introduced to half-life and radioactive particles. It takes roughly 40 minutes to complete both activities, depending on how many questions the students have. Sometimes I have a few of the students show the class how to do a problem on the board.

Part A is 2 pages and Part B is 3 pages. Students answer directly on the handouts.

Full answer key and teacher notes are included. The answer key explains how to arrive at the solutions.