Half Life of the M&Mium

Learning Goals
Explain isotopes, radioisotopes and how the parent isotope will decay into the daughter isotope using carbon 14 as an example. Include an explanation of a half life and how it can be used to predict the age of organic compounds

Perform this activity and complete a report using the format for the scientific method and the background information below.

As an example, the diagram below shows how a Nitrogen atom (amu 14) is converted to the radioisotope carbon 14 (parent isotope) and then decays back to Nitrogen 14 (daughter isotope).

/ The graph below shows the half-life decay pattern for any radioisotope from the radioactive parent isotope (solid line) back into the stable daughter isotope (dotted line).

We will assume that any M&Mium that is showing the letter “M” is still a parent isotope and M&Miums that are NOT showing the “M” have decayed into a daughter isotope.

  • Title (same as the activity)
  • Purpose: (Does the decay of "M&Miums" simulate natural the decay of radioisotopes?)
  • Background: (summarize the information given above or froma website)
  • Hypothesis: (Read the activity and then write a prediction based on whether or not you expect this activity to follow the same pattern as a radioactive isotope. State your reasons.)
  • Materials & Apparatus: (You and 2 (or 3) other friends each with a cup of M&Miums, graph paper and paper towel.)
  • Procedure: (You may copy the information below for your report)
  1. WARNING: People with allergies to M&M’s should not do this activity. Inform the teacher immediately if you have an allergy!
  2. Draw a table with the headings shown below

Year / Parent isotopes / Daughter isotopes
number / % / number / %
1
2
etc.
  1. Count the M&Miums in your cup, then return them to the cup. Your friends will do the same. This total of all your cups represents the total number of parent isotopes you’re beginning with and shall be entered in your table under year 1. The number of daughter isotopes in year 1 is “ZERO”..
  2. Gently shake each of your cups of M&Miums and pour them all onto the paper towel. This is year 2.
  3. For year 2, each of you will count the total number of parent isotopes (M showing), add them together and record that number in the appropriate column. The remaining M&Miums for everyone are daughter isotopes (M not showing) and that total number is entered in the column to the right. Now set your daughter isotopes aside as they have “decayed” and are no longer required for this activity. Return the parent isotopes to the cup.
  4. Repeat steps #4 and #5 above until there are no more parent isotopes remaining.
  5. When you are done, calculate the percentages for the numbers in each year.
  6. Plot a graph of the table above using the percentages on the y axis and the years on the x axis. There will be 2 lines to plot. One for the parent isotopes and one for the daughter isotopes.
  7. Clean up. You may now eat your M&Miums.
  • Observations: (Include your completed chart of values, the graph and any written observations.)
  • Conclusions: (answer the hypothesis, summarize the data, evaluate the activity.)