Wednesday, November 16 th, 2011 Bell Ringer: Using our 8 th Grade Average from yesterday, complete Table 2 of our Half-life Activity Handout. Half Life C-14 Period 1 C-14 Period 2 C-14 Period 3 C-14 Period 4 8 th Grade Ave

Half-Life % Predicted Atoms Remaining % Parent Isotopes Remaining ( 14 C) % Daughter Isotopes ( 14 N) 0100% 150% 225% 312.5% 46.25% Table 2. Number of Parent to Daughter Isotopes

Trilobite Fish Reptile Saber-toothed Tiger

Determining Ages To find the age of a substance: #half-lives X half-life of the element = AGE Example: 1.2 half-lives X 704,000,000 years= 844,800,000 years old

Fossil % Uranium- 235 % Lead-207 Trilobite60%40% Fish75%25% Reptile85%15% Saber-toothed Tiger95%5% Dr. Limestone’s Data

#half-lives X half-life of the element = AGE

Trilobite: Fish: Reptile: Saber-toothed Tiger:

Trilobite Fish Reptile Saber-toothed Tiger

Exit Card: On a sticky note, describe how scientists determine how old rocks are, using radioactive decay. Tomorrow’s Learning Goals: Exploration of Earth’s Past!

History of the Earth! Cambrian ___________ Triassic _____________ Ordovician __________ Jurassic ____________ Silurian ____________ Cretaceous _________ Devonian ___________ Tertiary ____________ Quaternary _________ Mississippian__________ Pennsylvanian _________ Permian ____________