Physical Science

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Breaking up is hard to do!

• Physical Science
• High School
• To Teacher Page
  
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  Activity

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Teacher Page

• Content Physical Science Atomic half-life
• Grade Level High School
• Creator Dorothy Walk
• MAP Standards SC 1
• IBD The learner will be able to determine the
  age of a sample of material if they know the
  half-life and amount of certain isotopes.
• Answer to problem 2 .3125 gram of Co

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Teacher Page--2

• Focus on the process of problem solving with your
  students..
• They need to understand not only the facts but
  the reasoning behind them.
• Have them write their thoughts on paper and then
  discuss them as a class

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Vocabulary words

• Half-life The time for one half of the atoms of
  a certain material to decay.
• Isotopes Atoms of same element with different
  number of neutrons.
• Radioactive element An element whose nucleus
  breaks down and gives off particles, radiation
  and energy.

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Types of Radiation

• Alpha particle Two protons and two neutrons
  (Helium nucleus
• Beta particle One electron
• Gamma rays Pure energy

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Think about...

• What are some positive uses of radiation?
• What are some negative uses of radiation?

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Did you think about

• Nuclear energy or nuclear bombs?
• Irradiated foods or X-rays?
• Radiation sickness or radiation treatment?
• Radon gas or Smoke detectors?

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Half-LifeOf Selected Elements

• 3H 12.3 years
• 14C 5730 years
• 131I 9.04 days
• 212Pb 10.6 hours
• 104Po 0.7 seconds
• 235U 7.04 x 108 years

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Iodine 131 (Half-life 8 days)

• Beginning amount 100 grams
• Day 8 50 grams
• Day 16 25 grams
• Day 24 12.5 grams
• Day 32 6.25 grams
• Day 40 3.125 grams

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Dating material

• Carbon-14 is found in all living and once-living
  things at a certain percentage. The half-life of
  Carbon-14 is 5730 years. Scientists determine
  how much Carbon-14 is remaining in the fossil or
  once-living item. From that, they can determine
  the approximate age of the material.

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Problem

• A fossil has been discovered. It has one eighth
  the amount of expected Carbon-14. What is the
  approximate age of the fossil?
• Hint One half of 1/2 1/4 One half of
  1/41/8
• One half of 1/8 1/16 One half of 1/16 1/32
  

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Solution

• The fossil has existed for 3 half-lives. (It
  takes 3 half-lives to get to 1/8.) The half-life
  of carbon is 5730 years. The fossil is at least
  17,190 years old.
• 5730 x 3 17,190

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Another Problem

• The half-life of Cobalt-60 is 11 minutes.
• How much Cobalt-60 is left after 1 hour if 10
  grams was used?

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Using What You Know

• Many medical procedures use radioactive isotopes
  to determine problems with the patient.
• Why are isotopes with a short half-life used for
  these procedures?

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The End