1
Q
How can you work out the age of rocks and fossils?
A
- radioactive dating
- by using the amount of radioactive isotope left in a sample, and knowing its half-life
2
Q
How does radiocarbon dating work?
A
- carbon-14 is an isotope of carbon found scarcely in the air and living things
- when living things die, they stop exchanging gases with air outside and carbon-14 is tapped inside
- it gradually decays
- by measuring the proportion of carbon-14 left in something old, can tell you how long ago the item was living material using the known half-life
3
Q
What are the relative proportions of uranium and lead at certain times?
A
- initially: 100% uranium, 0% lead (ratio of uranium to lead 1:0)
- after one half-life: 50% uranium, 50% lead (ratio of uranium to lead 1:1)
- after two half-lives:25% uranium, 75% lead (ratio of uranium to lead: 1:3)
4
Q
How do uranium isotopes form isotopes of lead?
A
-uranium isotopes have very long half-lives and decay to via a series of short-lived particles to produce stable isotopes of lead
5
Q
How can rocks be dated?
A
-using the relative proportions of uranium and lead in a sample of rock, and using the known half-life of uranium
