# Radiometric dating questions expiration dating of multidose vials

This age is computed under the assumption that the parent substance (say, uranium) gradually decays to the daughter substance (say, lead), so the higher the ratio of lead to uranium, the older the rock must be.

Of course, there are many problems with such dating methods, such as parent or daughter substances entering or leaving the rock, as well as daughter product being present at the beginning.

Most people are not aware of the many processes that take place in lava before it erupts and as it solidifies, processes that can have a tremendous influence on daughter to parent ratios.

Such processes can cause the daughter product to be enriched relative to the parent, which would make the rock look older, or cause the parent to be enriched relative to the daughter, which would make the rock look younger.

A number of processes could cause the parent substance to be depleted at the top of the magma chamber, or the daughter product to be enriched, both of which would cause the lava erupting earlier to appear very old according to radiometric dating, and lava erupting later to appear younger.

To me it has been a real eye opener to see all the processes that are taking place and their potential influence on radiometric dating.

In the first two columns below transfer your data from the previous table starting with the 1st half-life. What relationship do you see between the number of half-lives which have passed and the exponent used to express the fraction of heads remaining using exponential form? If I asked you what fraction of an element would be left after 5 half-lives could you come up with the answer using the information you have gathered above? What does the letter “x” stand for in this equation (think about your answer to number 1 above)?

INSERT TABLE HERE Formative Assessment - B Purpose: To demonstrate how using the half-lives of isotopes can use radiometric dating to find the age of a rock.

By measuring the amount of carbon-14 remaining, the age of the fossil can be determined.

Follow the steps listed below to illustrate the radioactive decay of carbon-14; then answer the questions: Each cut represents the half-life of carbon-14. Multiply the number of cuts by the half-life of carbon-14.