Wednesday, November 16th, 2011Bell Ringer:

Using our 8th Grade Average from yesterday, complete Table 2 of our Half-life Activity Handout.

Half Life

C-14 Period 1

C-14Period 2

C-14Period 3

C-14Period 4

8th Grade Ave.

0 100 100 100 100 1001 52 62 51 46 532 32 28 25 24 273 15.4 19 13 13 154 8.5 8.5 6 6.2 7.35 3.9 4.1 2.9 2.9 1.56 2.3 --- 1.4 2.0 1.4

Half-Life% Predicted

Atoms Remaining

% Parent Isotopes

Remaining (14C)

% Daughter Isotopes (14N)

0 100%

1 50%

2 25%

3 12.5%

4 6.25%

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

Trilobite 60% 40%

Fish 75% 25%

Reptile 85% 15%

Saber-toothed Tiger 95% 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 ____________