Radiometric dating game

EDS 1021 Week 6 Interactive Assignment

Radiometric Dating

Objective: Using a simulated practical application, explore the concepts of radioactive decay and the half-life of

radioactive elements, and then apply the concept of radiometric dating to estimate the age of various objects.

Background: Review the topics Half-Life, Radiometric Dating, and Decay Chains in Chapter 12 of The Sciences.

Instructions:

1. PRINT a hard copy of this entire document, so that the experiment instructions may be easily referred to,

and the data tables and questions (on the last three pages) can be completed as a rough draft.

2. Download the Radiometric Dating Game Answer Sheet from the course website. Transfer your data

values and question answers from the completed rough draft to the answer sheet. Be sure to put your

NAME on the answer sheet where indicated. Save your completed answer sheet on your computer.

3. SUBMIT ONLY the completed answer sheet, by uploading your file to the digital drop box for the

assignment.

Introduction to the Simulation

1. After reviewing the background information for this assignment, go to the website for the interactive

simulation “Radioactive Dating Game” at http://phet.colorado.edu/en/simulation/radioactive-dating-game.

Click on DOWNLOAD to run the simulation locally on your computer.

2. Software Requirements: You must have the latest version of Java software (free) loaded on your computer

to run the simulation. If you do not or are not sure if you have the latest version, go to

http://www.java.com/en/download/index.jsp .

3. Explore and experiment on the 4 different “tabs” (areas) of the simulation. While playing around, think about

how the concepts of radioactive decay are being illustrated in the simulation.

Half Life Tab – observe a sample of radioactive atoms decaying - Carbon-14, Uranium-238, or ? (a custom-

made radioactive atom). Clicking on the “add 10” button adds 10 atoms at a time to the “decay area”. There

are a total of 100 atoms in the bucket, so clicking the “add 10” button 10 times will empty the bucket into the

decay area. Observe the pie chart and time graph as atoms decay. You can PAUSE, STEP (buttons at the

bottom of the screen) the simulation in time as atoms are decaying, and RESET the simulation.

Decay Rates Tab – Similar to the half-life tab, but different! Atom choices are carbon-14 and uranium-238.

The bucket has a total of 1000 atoms. Drag the slide bar on the bucket to the right to increase the number

of atoms added to the decay area. Observe the pie chart and time graph as atoms decay. Note that the

graph for the Decay Rates tab provides different information than the graph for the Half Life tab. You can

PAUSE, STEP (buttons at the bottom of the screen) the simulation in time as atoms are decaying, and

RESET the simulation.

Measurement Tab – Use a probe to virtually measure radioactive decay within an object - a tree or a

volcanic rock. The probe can be set to detect either the decay of carbon-14 atoms, or the decay of uranium-

238 atoms. Follow prompts on the screen to run a simulation of a tree growing and dying, or of a volcano

erupting and creating a rock, and then measuring the decay of atoms within each object.

Dating Game Tab – Use a probe to virtually measure the percentage of radioactive atoms remaining within

various objects and, knowing the half-life of radioactive elements being detected, estimate the ages of

objects. The probe can be set to either detect carbon-14, uranium-238, or other “mystery” elements, as

appropriate for determining the age of the object. Drag the probe over an object, select which element to

measure, and then slide the arrow on the graph to match the percentage of atoms measured by the probe.

The time (t) shown for the matching percentage can then be entered as the estimate in years of the object’s

age.

After playing around with the simulation, conduct the following four (4) short experiments. As you conduct

the experiments and collect data, fill in the data tables and answer the questions on the last three pages of

this document.

http://phet.colorado.edu/en/simulation/radioactive-dating-game
http://www.java.com/en/download/index.jsp
http://www.java.com/en/download/index.jsp
Experiment 1: Half Life

1. Click on the Half Life tab at the top of the simulation screen.

2. Procedure:

Part I - Carbon-14

a. Click the blue “Pause” button at the bottom of the screen (i.e., set it so that it shows the “play” arrow). Click the “Add 10” button below the “Bucket o’ Atoms” repeatedly, until there are no more atoms left in the bucket. There are now 100 carbon-14 atoms in the decay area.

b. The half-life of carbon-14 is about 5700 years. Based on the definition of half-life, if you left these 100 carbon-14 atoms to sit around for 5700 years, what is your prediction of how many carbon-14 atoms will decay into the stable element nitrogen-14 during that time? Write your prediction in the “prediction” column for the row labeled “carbon-14”, in data table 1.

c. Click the blue “Play” arrow at the bottom of the screen. As the simulation runs, carefully observe what is happening to the carbon-14 atoms in the decay area, and the graphs at the top of the screen (both the pie chart and the time graph). Once all atoms have decayed into the stable isotope nitrogen-14, click the blue “Pause” button at the bottom of the screen (i.e., set it so that it shows the “play” arrow), and “Reset All Nuclei” button in the decay area.

d. Repeat step c. until you have a good idea of what is going on in this simulation. e. Repeat step c. again, but this time, watch the graph at the top of the window carefully, and click

“pause” when TIME reaches 5700 years (when the carbon-14 atom moving across the graph reaches