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Radiocarbon Dating Used to calculate the age of plant and animal remains While organism alive carbon-14 to carbon- 12 ratio stays same When organism dies,

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Presentation on theme: "Radiocarbon Dating Used to calculate the age of plant and animal remains While organism alive carbon-14 to carbon- 12 ratio stays same When organism dies,"— Presentation transcript:

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2 Radiocarbon Dating Used to calculate the age of plant and animal remains While organism alive carbon-14 to carbon- 12 ratio stays same When organism dies, carbon-14 decays without being replenished Puny scientists like Bruce Banner measure ratio of carbon-14 to carbon-12 to find how old organism is Used to calculate the age of plant and animal remains While organism alive carbon-14 to carbon- 12 ratio stays same When organism dies, carbon-14 decays without being replenished Puny scientists like Bruce Banner measure ratio of carbon-14 to carbon-12 to find how old organism is

3 Rate of Radioactive Decay Radioactive decay is measured using half-lives Half-life is constant for any radioisotope Half-life is the time it takes for half a sample of a radioisotope to decay Ex: Strontium-90 has a half-life of 29 years If you had 100g of strontium, after 29 years there would be 50g left Radioactive decay is measured using half-lives Half-life is constant for any radioisotope Half-life is the time it takes for half a sample of a radioisotope to decay Ex: Strontium-90 has a half-life of 29 years If you had 100g of strontium, after 29 years there would be 50g left

4 Decay Curve Graph of decay of radioisotope After each half-life, amount of radioisotope drops by half Graph of decay of radioisotope After each half-life, amount of radioisotope drops by half

5 Decay Curve

6 Common Isotope Pairs Isotope that decays called parent isotope Stable product(s) of parent isotope's decay called daughter isotope(s) On next slide, some common isotope pairs that can be used for radioisotope dating Isotope that decays called parent isotope Stable product(s) of parent isotope's decay called daughter isotope(s) On next slide, some common isotope pairs that can be used for radioisotope dating

7 Common Isotope Pairs Isotope Half-Life of Parent (y) Effective Dating Range (y) ParentDaughter Carbon-14Nitrogen Up to Uranium-235Lead million> 10 million Potassium-40Argon billion to 3 billion Uranium-238Lead billion> 10 million Thorium-235Lead billion> 10 million Rubidium-87Strontium-8747 billion> 10 million

8 Potassium-40 Clock Potassium-40 has a half-life of 1.3 billion years Its daughter isotope is argon-40 When rock is created from lava, the argon-40 is forced out leaving only potassium-40 After time the potassium-40 decays and creates argon-40 which gets trapped in the rock When scientists examine the rock they can use the amount of argon-40 to find the age of the rock Since these rocks were probably formed at the beginning of the earths life, the age of the rock is close to the age of the earth Potassium-40 has a half-life of 1.3 billion years Its daughter isotope is argon-40 When rock is created from lava, the argon-40 is forced out leaving only potassium-40 After time the potassium-40 decays and creates argon-40 which gets trapped in the rock When scientists examine the rock they can use the amount of argon-40 to find the age of the rock Since these rocks were probably formed at the beginning of the earths life, the age of the rock is close to the age of the earth

9 Potassium-40 Clock As the amount of potassium-40 decreases, the amount of argon-40 increases Using the graph and the ratio of potassium-40 to argon-40, scientists can find how old the rock is As the amount of potassium-40 decreases, the amount of argon-40 increases Using the graph and the ratio of potassium-40 to argon-40, scientists can find how old the rock is

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11 Quiz 1.Which two isotopes get compared in radiocarbon dating? 2.What is used to measure radioactive decay rate? 3.Does a half-life change for a given radioisotope? 4.What is a decay curve? 5.What is the daughter isotope of uranium-235? 6.What happens to the amount of argon-40 as the amount of potassium-40 decreases?

12 Answers 1.Carbon-12 and carbon-14 2.Half-life 3.No 4.A graph of the decay of a radioisotope 5.Lead The amount of argon-40 increases


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