Apply the scientific method to to investigate radioactive decay and its application to radiometric dating. . The activity involves experimentation using a web-based interactive simulation.

After completing the background reading for this assignment, go to the “Radioactive Dating
Game” simulation on the PhET simulations website at:
http://phet.colorado.edu/en/simulation/radioactive-dating-game. Click the play arrow on
the simulation graphic to run the web-based simulation or click DOWNLOAD to run the
simulation locally on your device.
Simulation requirements: This interactive simulation is optimized for use on computers
(MACs or PCs) and may not run on some tablets, notebooks, cell phones, or other devices.
Running the simulation will require an updated version of Java software (free). If you do not
or are not sure if you have Java on your computer, go to the Java Website. If you cannot get
the simulation to run, consult The PhET Simulation Troubleshooting Guide on the course
website.
2. Explore and experiment on the four different tabs (areas) of the simulation. While
experimenting, think about how the concepts of radioactive decay are being illustrated in
the simulation.
a. 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 100 atoms in the bucket; so, clicking the
add 10 button 10 times empties the bucket into the decay area. Observe the pie chart
and time graph as atoms decay. You can pause or step the simulation as atoms decay,
and Reset the simulation, using buttons at the bottom of the screen.
b. 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 1,000 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 or
step the simulation as atoms decay, and Reset the simulation, using buttons at the
bottom of the screen.
c. Measurement tab – Use a probe to virtually measure the amount of radioactive
material within an object or in the atmosphere. The probe can be set to detect the
decay of either carbon-14 or 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.
d. Dating Game tab – Use a probe to virtually measure the percentage of radioactive
atoms remaining within various objects and estimate the ages of objects by applying the
concept of half-life. The probe can be set to either detect carbon-14, uranium-238, or
other “mystery” elements that may be contained in the objects. 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.
e. Pause button ( I I ) – Simulation is running when this is showing; press to pause the
simulation.
f. Play arrow ( > ) – Simulation is paused when this is showing; press to run the
simulation.
3. After getting oriented to the simulation, follow the steps below to perform four different
experiments. Before beginning, be prepared to write down hypotheses and observations
for the experiments.
Experiments
Experiment 1: Half-Life
In this experiment, you will visualize the radioactive decay of atoms and investigate the concept
of half-life.
Before completing the experiment, write down a hypothesis, based on your current
understanding, that makes specific predictions for how the decay of a radioactive substance will
progress over time.
1. Experiment setup: click on the Half-Life tab at the top of the simulation screen.
2. Experiment procedure:

Construct a table like the one below. Complete the following steps for parts I and II of the
experiment to complete the table.
Part I – Carbon-14
a. Make sure that Carbon-14 is selected in the Choose Isotope box. Click the pause
button ( I I ) at the bottom of the screen so that it shows the play arrow ( > ). Click
the Add 10 button below the Bucket o’ Atoms ten times to empty the bucket and
place 100 carbon-14 atoms in the decay area.
b. The half-life of carbon-14 is about 5,700 years. Based on the definition of half-life, if
you left these 100 carbon-14 atoms to sit around for 5,700 years, what would you
predict to be the number of carbon-14 atoms that would radioactively decay
during that time? Write your answer down.
c. Click the play arrow. 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).
d. After all atoms have decayed, click the pause button, and the Reset All Nuclei
button in the decay area.
e. Repeat steps c and d until you have a good idea of what is going on. Then, write
down a specific description of what you observed happening, both in the decay
area and on the pie chart and time graph, while the simulation is in play mode.
f. Repeat step c again, but this time, watch the graph at the top of the window
carefully, and click “pause” when Time reaches 5,700 years, i.e., when the carbon-
14 atom moving across the graph reaches the dashed line labeled Half-Life. If you
don’t pause the simulation on or very close to the dashed line, click the Reset All
Nuclei button and repeat step c again.
g. Once you have paused the simulation in the correct spot, record the number of
carbon-14 nuclei that have decayed into nitrogen-14 (the number next to #14N, to
the left of the pie chart).