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10 Cards in this Set
- Front
- Back
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What is the origen of carbon dating?
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Scientists look for levels of carbon 14, a rare form of carbon that begins to decay and disappear as soon as an organisn dies. The older the object, the less C14 it will contain.
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Describe the carbon atom.
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Normal carbon atoms have 6 protons and 6 neutrons (carbon12). Sometimes cosmic rays entering the earths atmosphere will bombard nitrogen atoms, changing them into a special type of radioactive carbon called carbon 14.
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Carbon 14 has 2 more neutrons than normal carbon. T/F
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True. Over the course of 5,730 years, half of any given sample of C14 will decay back into nitrogen.
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What is the half life of Carbon 14?
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5,730 years.
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Can plants and animals distinguish between C14?
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No. They consume them both until they die, however, when a plant or animal dies, the levels of C14 in the organism start to decline. The C14 begins to decay, and because the organism is no longer consuming carbon, it is not being replenished.
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With reference to the above statement, the amount of C12 in the sample remains constant, as it is a stable molecule that does not decay. T/F
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True. To determine the age of a dead object, scientists compare its ratio of C14 to C12 to the ratio of an equivalent living object.
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Give an example of aging with C14.
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If a dead object has half the ratio of a living object, then it is app. 5730 years old, because C14 has a half life of 5730 years.
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What is the age if the ratio is 1/4 the living comparison.
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11,460 years old. If the ratio is 1/8, then the object is 17,190 years and so forth. If an object is much older than 60,000 years, there isnt enough Carbon14 left to be used scientifically.
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How are objects much older than 60,000 years old determined?
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Radioactive uranium has a half life of 704 million years and can be used to date objects on a geologic scale.
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Potassium 40, which is naturally found in the body has a half life of 1.3 billion years. T/F
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True. Willard Libby discovered carbon dating in the 1950s at the U. of Chicago.
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