PhET Activity for MS-LS4-1: Radioactive Dating Game

DIRECTIONS:
1. You should be on the 'Half Life' tab with 'Carbon-14' selected. This is the initial state.
2. Locate the 'Bucket o' Atoms' at the bottom of the screen.
3. Find the 'Add 10' button and the 'Play/Pause' button along the bottom.
4. Observe the pie chart and the graph at the top of the screen.
Spend 2-3 minutes exploring the 'Half Life' tab. Add some atoms and press play to see what happens. You can reset the simulation using the 'Reset All Nuclei' button. Do not move to the other tabs yet.

QUESTION: Are you acquainted with the tools in this simulation?

DIRECTIONS:
1. Ensure you are on the 'Half Life' tab. Click the 'Reset All Nuclei' button.
2. Make sure 'Carbon-14' is selected in the 'Choose Isotope' panel on the right.
3. Click the 'Add 10' button once to add ten Carbon-14 atoms to the screen.
4. Press the 'Play' button and watch one atom until it decays into Nitrogen-14.

QUESTION: Based on your observations of individual atoms, describe whether the decay of a single atom is a predictable or random event. Explain your reasoning.

DIRECTIONS:
1. Click the 'Reset All Nuclei' button.
2. Click the 'Add 10' button five times to add 50 Carbon-14 atoms.
3. Press 'Play' and let the simulation run for about 10,000 years on the timeline. Pause the simulation and note how many atoms have decayed.
4. Click 'Reset All Nuclei' again.
5. In the 'Choose Isotope' panel on the right, select 'Uranium-238'.
6. Click the 'Add 10' button five times to add 50 Uranium-238 atoms.
7. Press 'Play' and let the simulation run for the same amount of time (about 10,000 years). Observe how many atoms decay.

QUESTION: Which statement accurately compares the decay of Carbon-14 and Uranium-238?

DIRECTIONS:
1. Click on the 'Decay Rates' tab at the top of the screen.
2. Ensure 'Carbon-14' is selected on the right.
3. Click the 'Bucket o' Atoms' at the bottom left to add a large population of atoms.
4. Press the 'Play' button.
5. Observe the graph at the bottom. Watch the red line (Carbon-14) and note the time it takes to drop to 50%.

QUESTION: The ___ is the time it takes for ___ of the radioactive parent atoms in a sample to ___ into stable daughter atoms.

(a)  

DIRECTIONS:
1. On the 'Decay Rates' tab, click the 'Reset' button (orange arrow).
2. Make sure 'Carbon-14' is selected.
3. Click the 'Bucket o' Atoms' to fill the screen, you may have to click more than once.
4. Press 'Play' and pause the simulation exactly when the graph shows one half-life has passed (around 5730 years). Note the percentage of Carbon-14 remaining.
5. Continue playing and pause at the second half-life. Note the percentage again.
6. Continue playing and pause at the third half-life.

QUESTION: After a radioactive sample undergoes decay, different amounts of the parent isotope remain. Arrange the following percentages of parent isotope remaining in order from youngest (1 half-life) to oldest (4 half-lives).

DIRECTIONS:
1. On the 'Decay Rates' tab, click the 'Reset' button.
2. In the 'Choose Isotope' panel on the right, select 'Uranium-238'.
3. Click the 'Bucket o' Atoms' to fill the screen.
4. Press 'Play' and observe the x-axis (time axis) of the graph. Note the scale.

QUESTION: The half-life of Uranium-238 is significantly (a)   than the half-life of Carbon-14.

DIRECTIONS:
1. Click on the 'Measurement' tab at the top of the screen.
2. 'Tree' should be selected by default in the 'Choose an Object' panel on the right. If not, select it.
3. In the 'Probe Type' panel on the left, ensure 'Carbon-14' is selected.
4. Click the 'Plant Tree' button.
5. Drag the probe over the living tree and read the C-14 percentage. Then drag it over the air next to the tree and read the C-14 percentage.

QUESTION: While an organism is ___, it continuously exchanges carbon with the atmosphere, so its percentage of Carbon-14 remains ___. When it dies, it stops taking in new carbon, and its Carbon-14 begins to ___.

(a)  

DIRECTIONS:
1. Stay on the 'Measurement' tab with the 'Tree' selected.
2. If you haven't already, click 'Plant Tree'.
3. Click the 'Kill Tree' button.
4. Press the 'Play' button at the bottom and let time pass.
5. Periodically drag the 'Carbon-14' probe over the dead tree and observe how the percentage of C-14 changes over thousands of years.

QUESTION: Why does the amount of Carbon-14 in the tree only start to decrease after the tree dies?

DIRECTIONS:
1. On the 'Measurement' tab, click the 'Reset All' button (top right).
2. In the 'Choose an Object' panel on the right, select 'Rock'.
3. In the 'Probe Type' panel on the left, select 'Uranium-238'.
4. Click the 'Erupt Volcano' button.
5. Wait for the lava to cool and form a rock.
6. Press 'Play' and let millions of years pass. Use the probe to measure the U-238 in the rock over time.

QUESTION: Explain why the formation of igneous rock from lava 'starts the clock' for Uranium-238 dating. What does the 100% U-238 at the beginning represent?

DIRECTIONS:
1. Stay on the 'Measurement' tab with the 'Rock' object selected.
2. Ensure the volcano has erupted and a rock has formed.
3. In the 'Probe Type' panel on the left, select 'Carbon-14'.
4. Drag the probe over the igneous rock.

QUESTION: Based on its half-life and composition, Carbon-14 is not useful for dating very ancient fossils or rocks. For an 80-million-year-old dinosaur fossil, the amount of Carbon-14 remaining would be (a)   .