This activity is one that Rachel and I used for an NSTA meeting. Another student (Elizabeth), a Chemistry education major, wrote the lesson plan and the worksheets for the lab. This lesson is used to teach students the basic concept of radiation using M&Ms! When we did this lab with the students we had them perform all of their experiments and then they were able to eat the 'radioactive' pieces.
Make sure, when teaching this lab, to tell your students about the dangers, benefits and uses of radioactivity. A wonderful example is X-Rays, by using radioactivity and wavelengths to see through things!
Step One: Give each of your students a bag of M&M's. Our bag held about 130 pieces, you should use 100 pieces (or so) for each bag.
Step Two: Have the students count the M&M's.
Step Three: Have students place the M&M's back in the bag and lightly shake the bag up. (Since your M&M's are new they shouldn't fall apart as much as ours. Our M&M's have been used for this lab many times; and because they have been stored with Uraninite they are now slightly radioactive and inedible.)
Step Four: Pour out the M&M's on the table and separate the M&M's that have the M showing from those without.
Step Five: Count how many M&M's that have 'decayed.' These would be the M&M's with the letters showing. By doing this multiple times you are showing that each throw of the M&M's should produce around have with letters and half without. A simple demonstration for the concept of half life.
Step Six: Have the students repeat this procedure about 5-7 times. Remember to keep the M&M's that have decayed and the still active ones apart.
If you would like the lesson plan, activity sheet, or more information on this activity contact: notsysy.science.gmail.com