Since the half-life of carbon-14 is 5730 years, scientists can measure the age of a sample by determining how many times its original carbon-14 amount has been cut in half since the death of the organism.For example, an object with a quarter of its original amount (2x1/2) should be roughly 11,460 years old.Next, they will look at the graph of decay and see that when 25% of the parent isotope atoms are left, the isotope has gone through two half-lives.In this way, they get practice reading graphs and using them to understand and interpret data.Next, label each bag with a number (1-5), put it at a separate station around the room, and make a sign that identifies the parent isotope type and color, daughter isotope type and color, and half-life.For instance, your five bags might be set-up something like: When class begins, tell the students that in this activity they will use their knowledge of ratioactive decay and half-life properties to figure out the age of five different "fossils" at different stations around the room.Current methods include using the known decay rates of radioactive isotopes present in rocks to measure the time since the rock was formed.
These components have measurable properties, such as mass and electrical charge.
A good idea is to have the graph printed on the worksheet with the data table so that the students can have it right in front of them.
As shown in the diagram above, the radioactive isotope carbon-14 originates in the Earth's atmosphere, is distributed among the living organisms on the surface, and ceases to replenish itself within an organism after that organism is dead.
Instead of using exponents and natural logs, the students can just use a graph of predicted decay rates to determine the number of half-lives the isotope has gone through based on this percentage ().
For instance, in fossil one, the students will take 15 divided by 60 and come up with the percentage .25.Have the students rotate in groups from station to station until they have figured out the age of all five fossils.