Education Standards
Radiometric Dating Slides
Radiometric Dating Basics
Overview
A set of lessons that introduces the concepts of radiometric dating through lab, mini-lesson, and practice.
M&M Half-Life Lab
Make sure to prepare baggies of M&Ms with 50 in each bag.
This is usually best done in groups of two (splits M&Ms easier that way and is more cost effective).
You'll also need to label plates for as many groups as you will have. Reuse plates and cups to save money/trash as well.
Radiometric Dating and Half Life Lab
Materials:
- Baggie with 50 M&Ms
- Cup
- Plates
Procedure:
- NO EATING ANY M&MS UNTIL THE LAB TELLS YOU YOU CAN!
- Shake the M&Ms in the cup (NOT TOO HARD) for about 10 seconds and dump them out onto the plate labeled “POUR”.
- Count the number of M&Ms with the “m” down as you put them on the second plate labeled “M DOWN”. Record that value in the daughter column of the chart for the first pour. The “m” up amount (those left on the plate labeled POUR) should be recorded in the parent column.
- Leave the M&Ms on the M DOWN plate there. Take ONLY the remaining M&Ms that are “m” up ON THE PLATE LABELED POUR, and put them back in the cup. Shake those in the cup, and repeat the procedure from step 2. In the “m down” daughter column, put the total amount of “m down/daughter” M&Ms you have on the second plate. Record the “m up” amount in the parent column--not a total, just from the second pour.
- Continue the procedure until you have done 5 pours or there are no more m&ms on the POUR plate.
- Complete the chart by calculating the percentage of parent and daughter M&Ms for each pour.
- Check with your instructor that you’ve done it correctly and get permission to eat the m&ms.
- Answer the questions below the table.
| Pour | No. of parent | % of parent | No. of daughter | % of daughter |
| 0 | 50 | 100 | 0 | 0 |
| 1 | ||||
| 2 | ||||
| 3 | ||||
| 4 | ||||
| 5 |
1. Create a graph of your parent AND daughter M&M data with the following graph set up:
x-axis: pour
y-axis: number of M&Ms
Title: come up with an appropriate title for your graph.
2. Based on your graph, describe the trend in the amount of parent M&Ms with the amount of pours.
3. Based on your graph, describe the trend in the amount of daughter M&Ms with the amount of pours.
4. After how many pours did you have about ¼ of the original parent M&M?
5. Compare your chart to the chart of another group. Were your results the same? Why or why not?
Radiometric Dating Mini Lesson
Go over the slides as your teacher discusses them. It might be important to take notes in your own words as well.
Radiometric Dating Practice
Answers:
- Thorium-234
- 13
- Polonium-214
- We can figure out how much U-238 is present in a rock and compare that to the amount of daughter material. If we know that ratio (% parent to % daughter) we can look at the half life time and figure out how many half lives the rock has been through and then figure out the age. That’s how old the rock would be.
- Nitrogen-14
- 5,730 years
- 2
- 25%
- 75%
| Half Lives | Parent material | Daughter material |
| 0 | 30 g | 0 g |
| 1 | 15 g | 15 g |
| 2 | 7.5 g | 22.5 g |
| 3 | 3.75 g | 26.25 g |
| 4 | 1.875 g | 28.125 g |
- Royalium-77
- Reginon-30
- 10 hours
- 20 hours/2 half lives
- 3 half lives
Answer the questions on the radiometric dating practice document.