Nuclear Chemistry Day 2

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Nuclear Chemistry Day 2

• Thursday, Nov. 9th Monday, Nov. 13th
• Welcome! Today we will look over your quizzes
  and will revisit nuclear chemistry.
• The test over this unit will be Nov. 20-21st
• Hmwk
• Quiz over alpha/beta reactions and half-life
  equations. Bring your calculator!
• Interested in Honors? Your letter of intent will
  be due next Tues/Wed. Your science fair proposal
  will be due Nov. 22-23rd

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Warm-Up

• Write a reaction that would show how each of the
  following isotopes decayed.
• Uranium-232 (U) decays by alpha emission
• Plutonium-239 (Pu) decays by alpha emission
• Americium-243 (Am) decays by beta emission

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Agenda

• Announcements Honors Packet
• Warm-Up Alpha Beta Decay
• Notes Radioactive Half-lives
• Activity Half-Life Lab

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Radioactive half-lives

• Time for half the radioactive isotope to decay
  into other products
• Using half-lives, scientist can predict how old
  an object is.
• Examples Carbon-14 5.73 X 103 years
• Uranium-235 7.1 X 108 years
• Carbon -15 2.4 seconds

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Half-Life Carbon-14
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Sample problem

• Half-life Radium-226 has a half-life of 1599
  years. How long would it take seven-eighths of a
  radium-226 sample to decay?
• 1. List the given and unknown values.
• Given half-life 1599 years
• fraction of sample decayed 7/8
• Unknown fraction of sample remaining ?
• total time of decay ?

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• 3. Calculate the number of half-lives

Three half-lives are needed for one-eighth of the
sample to remain undecayed. 4. Calculate the
total time required for the radio-active decay.
Each half-life lasts 1599 years.
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Activity half-lives

• Purpose To model radioactive decay

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• Procedure
• Pour MMs out of cup and onto plate. Count the
  total number of MMs. Put this number in your
  data table. Pick out all the M side up candies.
  These candies have decayed. Record this in the
  decayed column of the data table and put them
  aside. Count the remaining MMs and list it on
  the table.
• Put the remaining MMs in a cup and pour them
  out again. Sort out the decayed and remaining
  and record that data. Take out the decayed and
  put the remaining back in the cup.
• Continue until they have all decayed.

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Results and Conclusion

• Results Graph the Half-life (Pour ) versus the
  amount remaining.
• Conclusion Questions
• How many half-lives did it take to completely
  decay the MMs?
• How did this lab accurately model radioactive
  decay?
• What is one inaccuracy in this model?