1 of 4

Half Life Lab

Name:

Class/Hour:

Learning Target: Calculate the age of fossils and/or rock layers using absolute dating. (1_F)

In this lab, you will model the radioactive decay of a radioactive isotope over time.

Materials:

2 of 4

Procedure:

Place all 100 candies with the letter M facing up. These are the original radioactive isotopes.

Place candy in cup or baggie and shake then roll the candy out of onto the napkin.

Set aside any candies facing down by placing them on the side (don’t eat them yet). These face-down candies will represent atoms of the isotope that have decayed into stable daughter atoms.

Count the remaining face up candies on the napkin and record in your data table.

Repeat steps 3-5 until all of your candies have “decayed”. You may add to your data table.

Start over, repeating steps 1-6 for a third trial. (You can eat your candy after the third trial.)

You start with 100 M&Ms instead of 300.

Time (Number of Half-Lives)	Amount of Radioactive Candies Remaining (%)
	Trial 1	Trial 2	Trial 3	Avg	Fraction or Percent of radioactive candy remaining (%)	In theory, what Fraction or Percent should be Remaining? (%)
0 (the start)	100	100	100	100	100/100 = 100%	100/100 = 1/1 = 100%
1^st half-life	45	53	50	49	49/100 = 49%	50/100 = ½ = 50%
2^nd half-life	22	27	28			25/100 = ¼ = 25%
3^rd half-life	15	12	11			12.5/100 = 1/8 = 12.5%
4^th half-life	7	6	5			6.25/100 = 1/16 = 6.25%
5^th half-life	3	2	2			3.125/100 = 1/32 = 3.125%
6^th half-life	1	1	2			1.5625/100 = 1/64 = 1.5625%
7^th half-life	1	0	1			0.78125 = 1/128
8^th half-life	0	0	1			0.390625 = 1/256
9^th half-life	0	0	0			0.1953125 = 1/512
10^th half-life	0	0	0			0.09765625 = 1/1024
	0	0	0
	0	0	0
	0	0	0
	0	0	0
	0	0	0
	0	0	0

Data Table:

The Effect of Time on the Amount of Radioactive Candies Remaining