Mathematical and Technological Literacy I Activity 3:  Radioisotope Dating

Please do the following at the beginning of every computer activity.

a. Open a new Word document. At the top of the document enter all group members names and last names, and Activity number.

b. Click on the Office Button in the upper left corner, then slide over "Save As".   Choose either "Word Document" to save your document as a Word 2007 document or "Word 97-2003 document" to save your document in an early version of Word.  If you are not sure which to choose, you should use "Word 97-2003 document".  When you are working on your document in class, first save the document to the desktop by setting the "Save in" textbox to "Desktop". (Saving to the desktop makes it easy to retrieve your work when you are finished.)  Your file name should be entitled something like "Group Activity 1".  Last, confirm the save as type in the last box.  (*.docx) is the suffix for a Word 2007 document.  (*.doc) is the suffix for early versions of Word. When you are leaving the class, upload your saved document into your Group files folder in D2L. That way if you completed your activity you can submit it via d2l dropbox, and if you are not yet finished you can access the partially completed file via D2L to complete it later.

How to save your file: Always save your work as .doc or .docx format.

Where to save your file: When working in class, save it on your desktop. When leaving class, always save your activity in the Group Files under your Activity Group in D2L. All work must be saved here. Additional options of saving such as email or flash drives are only back up methods and should not be used as primary modes of saving.

How to submit your activity: Once you complete your activity you need to submit it through D2L's Dropbox, under the correct dropbox for your activity. To ensure that you get evaluated and get a grade, make sure you submit before the deadline.

Deadlines are strict, no exceptions. Late submissions are not accepted. Incorrect submissions, submissions which cannot be opened due to wrong file type, or corrupt files will not be graded and will receive a grade of zero. Plagiarism receives a zero as a grade and will  be reported without exception.

Learning Goals for this Activity

1. You will understand the basic scientific concepts that underlay radioisotope dating.
2. You will learn about the essential characteristics of exponential decay.
3. You will be able to estimate the age of artifacts given the amount of a certain radioisotope with a known half life.

1. Some of the most famous Cro-Magnon cave paintings are located in Lascaux, France. On the right is an image from Lascaux. Charcoal found in the cave has approximately 14% of the carbon 14 found in living wood. Estimate the age of the paintings. Carbon 14 decays approximately 1.202% every 100 years. (Hint.  One way to approach this is to make a table in Excel that looks like Years After Formation % C 14  present 0 100 100 98.798 200 97.61045 Continue the table until the percentage of Carbon 14 is about 14%.)
2. (Age of moon) a.  Rock samples brought back from the moon by Apollo astronauts have approximately 58% of the original amount of Uranium 238 present. Using the fact that Uranium decays at a rate of approximately 7.41% every 500 million years, approximate how old the rocks are.  (Hint.  One way to approach this is to make a table in Excel that looks like Years After Formation % Uranium 238 present 0 100 500 92.59 1000 ...... Continue the table until the percentage of Uranium 238 is about 58%.) b. The rocks give an estimate for the age of the moon. What other issues would you need to take into consideration in using this method to date the age of the moon?
3. An analysis of charred oak from an excavated pit at Stonehenge allowed scientists to estimate that the structure was 3,800 years old. Estimate what percent of Carbon 14 remaining was found in the sample they tested. Carbon 14 decays approximately 1.202% every 100 years. Either copy and paste the portion of your table showing the answer or show the calculation used to answer the question.