Half-Life Lab
Materials:
100-200 M&M’s (plain), Skittles or pennies
Paper Plate (Large)
Plastic Cup
Black Marker
Procedure:
1. Count out between 100 to 200 M&M’s, Skittles or pennies and record the exact number. This will be your starting amount of undecayed radioactive isotope.
2. Place your M&m’s* in a cup. Pour the M&M’s* onto the paper plate carefully.
3. Count the number of M&M’s* with the Letter “m” up and record these as decayed isotopes. These may be eaten, but are no longer involved in the experiment.
4. Count the number of M&M’s* with the letter “m” down and record these as undecayed. Place these and only these M&M’s* back in the cup.
5. Repeat steps 2-4 six more times or until all of the M&M’s* are decayed.
6. Each time the M&M’s* are poured onto the plate, this represents a half-life.
Each half-life is 30 minutes.
7. Graph the data and explain the results.
* If using Skittles, if the letter “s” is up, then those are decayed. If pennies are used, then if the penny is “heads up” record these as decayed.
Questions
1.
Did your graph support that the half-life of the radioactive isotope was 30 minutes? Explain.
2.
Can you determine which atom will decay at a specific interval of half-life?
3.
How would your data change if each half-life was only 5 minutes or each halflife was 1000 years?
4.
Identify the independent variable and dependent variable on your graph.

Alternate Procedure
1.
With the black marker, mark off your plate into 2, 3, 4, 5 or 6 equal parts.
Make sure all lines go through the center of the plate (like your are cutting up a pie to divide the pieces).
2.
In one of the sections, place a “D” to signify “decayed” isotopes. In the other sections, place a “U” to identify “undecayed” isotopes.
3.
Count out between 100 to 200 M&M’s, Skittles or pennies and record the exact number. This will be your starting amount of undecayed radioactive isotope.
4.
Place your M&m’s* in a cup. Pour the M&M’s* onto the paper plate carefully.
5.
Count the number of M&M’s* in the section marked “D” and record these as decayed isotopes. These may be eaten, but are no longer involved in the experiment.
6.
Count the remaining M&M’s* in the section(s) marked “U” and record these as undecayed. These are placed back into the cup after being counted and recorded.
7.
Repeat steps 4-6 six more times or until all isotopes are decayed.
8.
Each time the M&M’s* are poured onto the plate represents 30 minutes.
9.
Graph your data and explain.
* Skittles or pennies may be used instead.
Questions
1.
From your graph, what was the half-life of your isotope? Identify how many sections your plate had.
2.
Can you determine which atom will decay at a specific interval of half-life?
3.
Identify the independent variable and dependent variable on your graph.
4.
How might your data and half-life change if your plate had more sections?
5.
How might your data and half-life change if your plate had fewer sections?