Chain Reaction

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					                                   Chain Reaction
                                      Mrs. B-Z

Name: ______________________________________________ Score: _____/60

The year is 1939 and the threat of the Nazi army looms all around. You
will be divided into the four teams of researchers who will look at different
aspects of the nucleus in order to learn how a nuclear chain reaction

   A. Location: Princeton University (15 points)
       Researchers: Neils Bohr, Ernest Rutherford and John A. Wheeler
       Bohr’s earliest views of the atom viewed the atom’s nucleus as a big drop which
   could be subdivided into a smaller drop. Rutherford discovered the nucleus was a
   small area of the atom with a positive charge. Around 1939, Bohr worked with
   John Wheeler (who was at Princeton) to hypothesize that the one isotope 238U
   underwent fission only when bombarded by fast, high-energy neutrons; whereas,
      U would undergo fission only with slow, thermal neutrons.

Define these Key Ideas: Look these up in your book’s glossary or index if you forget
what they mean. (6 points—1 point each)

   1.   Proton: ____________________________________________________________________
   2. Electron: ___________________________________________________________________
   3. Neutron: __________________________________________________________________
   4. Mass number: ______________________________________________________________
   5. Atomic number: ___________________________________________________________
   6. Isotope: ____________________________________________________________________

Activity: Using counting chips simulate the nucleus of 235U,
                           U, and 234U

Use RED chips for neutrons, YELLOW chips for protons, and BLUE chips for electrons.

Complete this chart: (9 points—0.5 point per space)
 Isotope Atomic        Mass       Number       Number of       # of           Teacher’s
         Number        number     of protons neutrons          electrons      initials for
                                                               (charge is     each
                                                               zero)          isotope



                                    92         protactinium ← uranium → neptunium
                                   (Uqb)                             periodic table
                                  Name, Symbol, Number uranium, U, 92
                                  Chemical series          actinides
                                  Group, Period, Block     ?, 7, f
                                                           silvery gray metallic


                                  Atomic mass              238.02891(3) g/mol

B. Location: Sweden (15 points)
   Researchers: Lise Meitner and Otto Frisch (Lise’s nephew)
   These two researchers are interested in finding out how the uranium splits.
   results. As Meitner and Frisch searched for an explanation, it dawned on them
   that when the uranium nucleus absorbs a neutron, it might become unstable
   and split into two particles of approximately equal mass (e.g., barium and
   krypton). They used Bohr’s earlier model, which treated the nucleus as a large
   drop of liquid. In this model, the absorption of a neutron could cause the
   uranium nucleus to become unstable and divide into two smaller drops. If this
   division takes place, the resulting drops (nuclear fragments) would be repelled
   by their respective positive charges. This process, termed fission by Meitner and
   Frisch, would create a large amount of energy, as well as additional neutrons.
   They calculated the energy associated with pushing the two positively charged
   nuclear fragments apart to be approximately 200 million electron volts (MeV)
   per uranium atom. By comparison, the most energetic chemical reactions
   release approximately .000005 eV per atom.

   Key Terms—If you do not recall the definitions for these terms, use your book’s
   glossary or index. (4 points—1 point each)

   1.   reactant: ______________________________________________________________

   2. physical change: ____________________________________________________

   3. chemical change: ___________________________________________________

   4. product of a chemical reaction: _________________________________________

        Activity: Simulate this reaction with chips.
     U + 1 neutron  236 U (which is unstable)  89Kr + 144 Ba + lots of energy

1. Create just the nucleus since that is what is undergoing the reaction in this
   nuclear reaction.
2. Fill in the table below to figure out how many of each type of chips you will
   need in each section. Note: You will only need a maximum of 236 chips.

Fill in this table: (8 points—0.5 point per box)
 Isotope Mass number             Atomic Number       # of neutrons    # of protons

3. Use RED chips for neutrons and YELLOW chips for protons.
4. Create the original nucleus of the 235U then add one extra chip for the
   neutron bombardment which starts the nuclear reaction.
5. Now put the single red chip in with the 235U isotope creating the unstable
   isotope 236U.
6. Now simulate the nuclear reaction. Divide the nucleus into 89Kr and 144 Ba.
7. Get your teacher’s initials. _____________________
8. Answer these questions.

1. This is a (circle one: chemical or physical reaction). (1 point)

2. The 236U isotope is the (circle one: reactant or product). (1 point)

3. The 89Kr and 144Ba are (circle one: reactant or product). (1 point)

C. Location: Niels Bohr Institute in Copenhagen, Denmark              (15 points)

          Researcher: Otto Frisch (before Nazi occupation on April 9, 1940)
          Frisch now is moving on to discover how there is so much energy coming
          from a single reaction. You are going to simulate the two types of reactions
          (non-nuclear vs. nuclear) to understand how the nuclear reactions are
          yielding such high amounts of energy.

Key Terms: Define these terms using your book or notes. (4 points—1 point each)

              1.   fission: __________________________________________________________

              2. nuclear chain reaction: ___________________________________________


              3. critical mass: _____________________________________________________

              4. Mass-Energy Equation ____________________________________________

         Activity: Simulating the Energy from a small
                      amount of uranium
Non-nuclear reaction simulation:

   Obtain 25 dominoes. Line them up standing on their narrower end so they
   will easily fall. Set them up so that each falling domino causes another
   domino to fall.

Teacher’s Initials: _____________________ (4 points)

Nuclear chain reaction simulation:

  Obtain 25 dominoes. Line up the dominoes on their narrower end, but this
  time instead of one domino only causing one other domino to fall, stack the
  dominoes so that one domino causes two dominos to fall and two dominoes
  cause three to fall and so forth until you have used all 25 dominoes.

Teacher’s Initials: _____________________ (4 points)


       4. In both simulations, one domino causes 25 other dominos to fall.
          Which reaction is faster? Circle one: non-nuclear or nuclear (1 point)

       5. What is the difference in terms of time for the reactions to take
          place? Was the faster reaction a lot faster or only slightly faster?
          ______________ (1 point)

       6. Which reaction will produce a lot more energy? (circle one: nuclear
          or non-nuclear) (1 point)

D) LOCATION: Long Island, NY and Chicago, IL (15 points)

                 Researchers: Einstein, Fermi, and Szilard

                 Compose a letter to President Franklin D. Roosevelt explaining the
                 need of further research funding of nuclear chain reactions for the
                 purpose of nuclear power and nuclear weapons. Also, balance the
                 need for caution concerning the power of this technology if the Nazi
                 Germans were able to produce nuclear power and nuclear weapons.

                 You may need to look up some information concerning nuclear
                 power and nuclear weapons online or in your book.

                 1.   Make a list of pros (positives) of nuclear power (remember this is
                      a Pre-World War II society) (3 points)

                 2. Make a list of cons (negatives) of nuclear power (again
                      remember this is before World War II) (3 points)

3. Make a list of pros (positives) of nuclear weapons (Although this
   is before World War II, it could be used as a deterrent to Nazi
   Germany.) (3 points)

4. Make a list of cons (negatives) of nuclear weapons. (If Nazi
   Germany found out how to use this first, how would it have
   changed the war? ) (3 points)

5. Now take your pro and con lists and formulate them into a well-
   written letter to President Franklin Roosevelt. (3 points)

August 2, 1939

F. D. Roosevelt
President of the United States
White House
Washington, D.C.

Dear Sir:

Relatively Yours,

Albert Einstein
Old Grove Rd.
Nassau Point
Peconic, Long Island


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