Integrated Science 2 Name: Per

Graphing Radioactive Decay Integrated Science 2 Name: Per:

Introduction Radioactive dating is a very important tool in determining the age of fossils and rocks. In this activity, you will construct graphs to illustrate the decay of various radioactive elements.

Procedure Begin by completing the data tables for each of the radioactive elements. Then graph your data, and use your graph to answer the questions. 1. Uranium 238 (Half-life= 4.5 billion years) Time (billions of years) Percent of Original Material Unchanged (%) 0 100 4.5 50 9.0 13.5 18.0

a) You find a rock that has 12.5% of its Uranium 238 remaining unchanged. What is the approximate age of the rock? (Hint: use your graph.) b) You find a rock that has 35% of its Uranium 238 remaining unchanged. What is the approximate age? c) Would Uranium-238 be useful in dating something 10,000 years old? Explain.

2. Carbon-14 (Half-life= 5,568 years) Time (years) Percent of Original Material Unchanged (%) 0 100 5,568 a) You find a skeleton with 65% of its original carbon-14 remaining unchanged. How old is the skeleton?

b) Would Carbon-14 be useful in dating something 10,000 years old? Explain.