Thursday, Feb. 24, 2011

• Objective: Students will be able to describe Radiometric Dating techniques.

• Bellringer: Contrast Relative Dating and Radiometric Dating of fossils.

Bellringer Review

• Objective: Students will be able to describe Radiometric Dating techniques.

• Bellringer: Contrast Relative Dating and Radiometric Dating of fossils.– Relative Dating:

• Tells the relative age of fossils (older or younger)• Based on depth fossil is buried in the Earth

– Radiometric Dating:• Tells the exact age of fossils• Based on amount of radioactive isotopes in fossils

Lab Report

• Title• Purpose• Hypothesis• Materials• Procedure• Data Analysis• Conclusions

• In today’s lab, you will have to write your own Lab Report, which will include all the parts on the left.

• On the following slides, write down everything that is UNDERLINED to include in your report.

Title:Dating Materials Using Half

Life of “Harlanium-96”Thursday, February 24, 2011

“Sue” the T-Rex in Chicago

Purpose:To use Radiometric Dating to

Date Fossils.

Ancient Fish

• Radioactive isotopes are atoms that break down into other atoms over time.

• Scientists can measure the number of radioactive atoms in an object to calculate the age of the object.

Hypothesis:We will be able to know the ages of fossils based on a Radiometric Dating graph.

Ammonite

(big sea animal in shell)

Materials:

• 100 pennies

• Shoe box

• Graph paper

• Fossils

Procedure:Part 1: Creating A Half Life Curve

• Place 100 “atoms” (pennies) in a shoe box.• Shake the box once and remove any

“atoms” that have “decayed” (landed heads down).

• Count the remaining atoms and use this as the number of atoms remaining after the first half life.

• Record this number in your Data Table and plot the point on your Graph.

Procedure continued

• Continue shaking, counting, and removing for an additional 4 half lives (5 total).

• Once you have finished your Table and Graph, have your teacher verify that everything is correct before moving on to Part 2.

Data Analysis:Data Table

Draw this Data Table on your Lab Report.

Half Life Years Passed

(millions)

Number of Atoms

Remaining (billions)

0 0 1001 100  2 200  3 300  4 400  5 500  

Data Analysis:Radiometric Dating Graph

Draw this graph on your graph paper.

Procedure: Part 2:Dating Samples

• In Part 1, you created an “ideal” half life graph with your pennies. Now use that to…

• Determine the age of three different fossil samples (from those labeled A, B, C, D, or E).

• To help you do this:– Assume every sample originally contained 100 billion

atoms.– Assume the sixth half life represents 2011.– Know the half life of Harlanium-96 is 100 million

years.– Use the amount of Harlanium-96 atoms remaining in

the sample to figure out age.

Data Analysis: Dating Samples

For each fossil sample:1. Label, with the letter, on the Graph where

the sample belongs.

2. Determine how old the sample is based on your graph.

3. Label what period and era the sample comes from. (p. 374)

4. Give an example of what type of organism could make up your sample. (p. 374)

Conclusion Questions:

1a) What is the name of the two elements that are used by scientists to date fossils?

1b) Which element is used for really, really old fossils?

2) How old is the Earth and how are scientists so sure of this number?