Stream Abrasion Lab

The Frederick Douglass Academy Name: ______Earth Science/Mr. Valeiras/Pd.___ Date: ______Class:______

Radioactive Decay Lab INTRODUCTION : Some isotopes spontaneously emit particles or energy to yield a different element or isotope. This is called radioactive decay. This decay occurs naturally and is not affected by temperature, pressure, or chemical change. Radioactive decay takes place at a random rate. Although you cannot predict just when any given atom will decay, you can predict that of the billions of atoms within a small piece of a radioactive element, a given number will decay at a regular and predictable rate.

OBJECTIVE : You will collect model statistics which show how the rate of radioactive decay of an isotope can be used to determine the absolute age of a rock.

CATALYST :

# of Half Lives Years % Daughter % Parent Drawing

1 200 years

VOCABULARY :

Isotope – ______Half-life – ______Radioactive Decay – ______Radioactive dating – ______Parent isotope – ______Daughter isotope (product) – ______

PROCEDURE A : The Frederick Douglass Academy Name: ______Earth Science/Mr. Valeiras/Pd.___ Date: ______Class:______

1. Place 100 atoms (pennies) into the container 2. Place lid on box and shake for 15 seconds 3. Remove lid and take out the decayed atoms (represented by “tails up” showing) 4. Count the number of undecayed atoms (represented by “heads up”) left in the box 5. Enter the number of decayed (removed) and undecayed (remaining) into Table 1. 6. Repeat steps 2-5 until all the atoms have decayed 7. Collect data from your classmates to determine the class average for each section. 8. Use the class average to determine the percent of markers removed at the end of each trial using the equation below.

% Removed = . number of pennies removed . x 100 number of pennies shaken

9. On GRAPH #1, plot the class average of the number of pennies that remained for each trial. 10. On GRAPH #2, plot the class average of the percent of pennies that were removed per trial.

Trial # # Shaken Class Average # Decayed Class Average # Undecayed Class Average % Pennies Shaken (Removed) Decayed (Remaining) Undecayed Removed 0 100 100 0 0 100 100 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

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i s a s a m l e C R The Frederick Douglass Academy Name: ______Earth Science/Mr. Valeiras/Pd.___ Date: ______Class:______

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PROCEDURE B : 1. a. On the vertical axis of GRAPH #1, find a value which is one half-life (50%) of the number you had at the start. Draw a horizontal line from the vertical axis over the graph line. b. Where these two lines meet, draw a vertical line down to the scale for trial number. Record to the nearest tenth of a trial number on Report Sheet #2. 2. Repeat Procedure B-1 substituting the following points on the vertical axis: 25% of the original number + 12.5% of the original number DISCUSSION QUESTIONS :

1. According to Procedure B what is the half-life for the model atoms in this experiment?

Trial # The Frederick Douglass Academy Name: ______Earth Science/Mr. Valeiras/Pd.___ Date: ______Class:______

2. Assuming each trial is equivalent to a million years, determine the half-life of the model from Question #1.

3. According to GRAPH #2, what was the percent of decay for each of the first four atoms?

4. Explain why there was a change in the percent of decay for this model during the last few trials.

5. Why would the half-life be unaffected if you increased the number of atoms (pennies) at the beginning?

6. Why were class averaged used instead of just your own data?

CONCLUION: The Frederick Douglass Academy Name: ______Earth Science/Mr. Valeiras/Pd.___ Date: ______Class:______

What are the similarities between this model and radioactive decay in nature?

RADIOACTIVE DECAY LAB RUBRIC Catalsyt 0 Not completed. 1 Partially complete. May be 2 All sections filled in incorrect. thoroughly and correctly Vocabulary 0 Almost no words 1 Most words present and defined. 2 All words present and clearly defined or missing May be insufficient definitions, or defined entirely. missing definitions. Report 0-1-2 Incomplete, 3-4-5-6 Mostly complete and 7-8-9-10 Complete and Sheet #1 or missing entirely. accurate. May be missing class thorough. Columns 2-7 averages. completely filled in. Graph #1 0-1 Incomplete, or 2-3 Mostly complete and accurate. 4-5-6 Complete and thorough. missing entirely. Includes labels. Includes labeled axes. Graph #2 0-1 Incomplete, or 2-3 Mostly complete and accurate. 4-5-6 Complete and thorough. missing entirely. Includes labels. Includes labeled axes. Discussion 0-1-2 Incomplete, 3-4-5-6 Mostly complete and 7-8-9-10 Complete and Questions or missing entirely. accurate. Effort could have been thorough. Clear presence of better. effort. Conclusion 0-1 Incomplete, or 2-3-4 Mostly complete and 5-6 Complete and thorough. At missing entirely. accurate. Includes less than three least three sentence description. factors.

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