1. Carbon 14, an isotope used to date recent organic remains, would most likely be useful in determining the age of a fossil A. Beluga whale B. Trilobite C. Coelophysis D. Armored fish
2. The characteristics of the radioisotope uranium 238 that makes it useful for accurately dating the age of a rock is the istopes A. resistance to weathering and erosion B. constant half life C. common occurence in sediments D. organic origin
3. Uranium 238 that crystallized at the same time Earth formed has undergone approximately how many half lives of radioactive decay? A. four half lives B. one half life C. two half lives D. three half lives
4. The absolute age of a rock is the approximate number of years ago that the rock formed. The absolute age of an igneous rock can best be determined by A. comparing the sizes of the crystals found in the upper and lower parts of the rock B. comparing the amounts of decayed and undecayed radioisotopes in the rock C. examining the environment in which the rock is found D. examining the rocks relative position in a rock outcrop
5. A sample of wood that originally contained 100 grams of carbon 14 now only contains 25 grams of carbon 14. Approximately how many years ago was this sample part of a living tree? A. 2850 years B. 11400 years C. 17100 years D. 5700 years
6. A rock contains 5 grams of Uranium 238 and 35 grams of Lead 206. How old is the rock?
7. A rock contains 5 grams of carbon 14 and 75 grams of Nitrogen 14. How old is the rock?
ANSWERS
1. A ( it was once living and is less than 50,000 years old)
2. B
3. B (Because the age of the Earth is approximately 4.5 billion years)
4. B
5. B
Mass remaining
Time
100
0
50
5,700
25
11,400
6. 13.5 billion years (The key to this one is that if you start with 5 grams of Uranium and 35 grams of Lead, they must add up to the original amount of the parent, which would be 40 grams)
