The United States: Radioactive Dating

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The United StatesRadioactive Dating

• Half Life and Carbon 14

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What is Radioactive Dating?

• A technique that gives absolute ages of a
  material (rather than rough estimates) from the
  number of radioactive atoms remaining in the
  material.
• Incorporating of C14 into living material in
  plants by photosynthesis, in animals by
  integrating plant materials
• C14 is the radioactive form (isotope)
• ½ life of C14 is 5730 yrs.
• By knowing the rate of radioactive decay and by
  counting C14 in the fossil, the age of the matter
  can be estimated.

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What Is Carbon-14 Dating?

• A way of determining the age of certain
  archeological artifacts of a biological origin up
  to about 50,000 years old.
• A chemical analysis used to determine the age of
  organic materials based on their content of the
  radioisotope carbon-14 believed to be reliable
  up to 40,000 years
• It is used when trying to find the date of things
  such as bone, cloth, wood and plant fibers that
  were created in the past by human activities.
• (Carbon-14 is radioactive, with a half-life of
  about 5,700 years)

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How Is Carbon-14 Made?

• 1- Cosmic rays enter the earths atmosphere and
  collide with an atom, therefore, creating an
  energetic neutron.
• 2- When the neutron collides with a nitrogen
  atom, a nitrogen-14 atom turns into a carbon-14
  atom (and a hydrogen atom).
• 3- From there, plants absorb carbon dioxide and
  incorporate carbon-14 through photosynthesis
• 4- Animals and people eat plants and take in
  carbon-14
• 5- Following death and burial, wood and bones
  lose Carbon-14 as it changes to Nitrogen-14 by
  beta decay

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Process
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Half Life

• The time required for one-half of a radioactive
  material to decay to a more stable material
• The time required for half the nuclei in a sample
  of a specific isotopic species to undergo
  radioactive decay.
• Isotopes decay at different rates
• Follows exponential decay

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Figures

• The half-life of carbon-14 is 5,730 years. It
  will take 5,730 years for an overall amount of
  carbon-14 to decrease by half in an organism.

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Vocab

• Cosmic Rays - Nuclear and subatomic particles
  moving through space at speeds close to the speed
  of light. They are thought to come from stars in
  the Milky Way galaxy.
• Photosynthesis - a process used by plants to
  convert water, carbon dioxide, and sunlight into
  carbohydrates and oxygen. The oxygen in the
  Earth's atmosphere is produced by this process.
• Beta Decay - A nuclear reaction in which beta
  particles (electrons, -, or positrons, ) are
  absorbed by or emitted from the nucleus of an
  atom.

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Analogy Half Life

• Half life is like a house party. For example, at
  12am half the people at the party leave while
  half stay. The party is now more stable and
  controllable, just like half life!