Learning Exercise

Title: Rock Dating Concept: Radioactive Decay (Absolute Dating) as it pertains to finding the half-lives of igneous rock. Grade Level/ Standards: 7th Grade Life Science/ 3. Biological evolution accounts for the diversity of species developed through gradual processes over many generations. As a basis for understanding this concept: c. Students know how independent lines of evidence from geology, fossils, and comparative anatomy provide the bases for the theory of evolution. 4. Evidence from rocks allows us to understand the evolution of life on Earth. As a basis for understanding this concept: d. Students know that evidence from geologic layers and radioactive dating indicates Earth is approximately 4.6 billion years old and that life on this planet has existed for more than 3 billion years. Goals: For students to understand the concept of radioactive decay by working on “Virtual Dating,” an interactive website. Specific Objectives: Students will understand that when an igneous rock forms it contains 100% of the parent isotope. As time passes by in thousands or millions of years, some of the parent isotopes lose an electron and makes them daughter isotopes. The time it takes for half of the parent isotope to become daughter isotope is called a half-life. When ¾ of the parent isotope becomes daughter isotope, another half life has gone by and so on. Materials: Paper, Pencil, Computer Anticipatory: Scientist can determine the age of the Earth by examining the atoms (elements) found in igneous rock. Chemistry: describe the composition of atoms (protons, neutrons, and electrons). When an electron is lost, a whole new element is created. Parent isotopes are unstable and want to become a stable daughter isotope. Step by Step: Day 1: 1. Class discussion on the age of the earth and how scientists are able to determine the age of rocks using Power Point. (30 min). 2. Demonstrate how to get to http://www.sciencecourseware.org/VirtualDating/ and how to use the website using an LCD projector along with an interactive pad so the students can practice while everyone else watches on the screen. Day 2: 1. The students will be going to the computer lab. 2. I would give the students a brief review of what to do on the website while they work independently answering the questions on the screen and on a separate piece of paper to turn in at the end of class. Day 3: 1. Students will be getting their papers back at the beginning of class. 2. I will show the website on the LCD projector in order to go through the website as a class. 3. The students will take turns using the interactive pad as we go through the website and answer the questions and discuss them. Independent Practice: The students will be working independently at the computer lab. They will also be motivated to visit the website at home and practice using it before we go to the computer lab. Closure: The students will write a paragraph to describe how scientists date igneous rocks after going over the questions and discussion. This will also serve as an assessment for the information that the students have learned in the past three days. Adaptations: Students who need extra assistance and with learning difficulties will be paired with a student who will best meet his or her needs while working on the computer. I will also be walking around the computer lab to assist any student who needs the help. Extensions: Gifted students will provide a diagram to demonstrate the concept of radioactive decay on an assigned common isotope found in rocks. They will then demonstrate their diagram to the class so they can benefit from their information. Connections: This activity can be easily correlated to relative dating and the law of superposition. This is a good introduction to fossils and evolution.