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How can we explain absolute dating?
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?
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Elements Ex: Carbon (C), Helium (He)
Exist in varieties called Isotopes Isotopes differ slightly in mass Ex: Carbon-14 and Carbon-12
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Radioactive Decay Unstable isotopes are radioactive
Emit particles and energy through radioactive decay
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Carbon-14 Nitrogen-14 Uranium-238 Lead-206 The ability of radioactive elements to decay into different elements This decay continues until stable isotope emerges
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Carbon-14 The most useful element in dating organic material
Ex: plants and animals
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Half-Life Time required for half the atoms in a sample to decay
Independent of mass, temperature, and pressure
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Carbon -14 video How do scientists use carbon 14 for dating?
Does the carbon-12 in organisms ever change?
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Carbon - 14 What is the half-life of carbon-14? 5,700 years
Predict what ages carbon-14 would be best for Less than 50,000 years
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You have 100 g of a substance that has a half-life of 1 hour
Time (hours) Mass # of half-lives Amount of substance left 100 g 1 50 g 1/2 2 25 g 1/4 3 12.5 g 1/8 4 6.25 g 1/16
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Percent of Carbon -14 remaining
Radioactive Decay 120 100 Percent of Carbon -14 remaining 80 60 40 20 1 2 3 4 5 6 Number of Half-Lives
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A fossil you found has equal amounts of C-14 and N-14
A fossil you found has equal amounts of C-14 and N-14. How many half-lives have passed? How much time? C-14 N-14 In 1 half-life, half of the C-14 would be N-14. According to the ESRT, 1 half life of C-14 is 5.7 x 103 years, or 5700 years.
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