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Grade Level: High School

Subject: Physics

Objectives:

1. Students will simulate radioactive decay and half-life over time and graph the data.

2. Students will understand the components of radioisotopes.

3. Students will predict the nuclear equation for unstable nuclei.

4. Students will evaluate the accuracy of radioactive dating.
    

 Illinois State Goals:

Goal 11: Understand the  of scientific inquiry and technological design or investigate questions, conduct experiments and solve problems.

1. 11.A.3f    Interpret and represent results of analysis to produce findings.

2. 11.A.4d   Apply statistical methods to the data to reach and support conclusions.

3. 12.C.3a   Explain interactions of energy with matter including of state and conservation of mass and energy.

4. 12.C..3b  Model and describe the chemical and physical characteristics of  matter (e.g. atoms, molecules,
                   elements, compounds, mixtures)

Estimate Time: two or more 50 -minute periods, not including enrichment assignment

Internet Link:
http://library.thinkquest.org/3471/radioactive_dating.html?tqskip1=1

Pre-Lab Discussion:
 

1. Teacher will lead students into a discussion about radiation and how it can be used. Ex. ( sun, x-rays, dating of materials)
2. Students will be given simple addition and subtraction problems with one variable missing to assess their problem solving
   skill.  This information will used to group students cooperatively by ability.  ( 2- strong, 2-weak)

Definitions and Concepts:

Radioactivity results from the spontaneous decay of an atom's nucleus.  There are three main types of nuclear decay: alpha, beta , positron,  and gamma.  Each results in a characteristics change in the parent nucleus and is characterized by the formation/ejection of a specific particle or electromagnetic radiation.

Describe each type of decay showing the particle.

Alpha:

Beta:

Electron Capture:

Positron:

Gamma:

Teaching Strategy:  Have students work in cooperatively for lab activity.  Students will use rubric to evaluate how well they work with each other as a group. Teacher will used same rubric to evaluate individual student performance during the activity.

Activity :

Materials:

• 300 chips that have one white side and one side black
• textbook with periodic table
• graph paper
• pencil
• ruler

Procedure:

• Place 300 white/black chips into a cup. 
• Put your hand over the top of cup and shake thoroughly, dumping chips onto a flat surface or desk. 
• Count the number of chips that display the white surface. 
• Enter that  number into the table for first toss, then put the rest of the chips back into the cup and repeat throwing and   
  counting white chips until there are no more chips in the cup. 
• Enter the number of chips that are white from each toss into the table below.   
• Using the data from the table design a  graph with # of white chips left as the y-axis and #tosses as x-axis.
  (Note: The tosses represent the half-life and the number of chips represents the amount materials that has decayed.
                                                                                                        

Note: The first toss is the first half-life(1/2).  The second half-life is (1/4) , third half-life (1/8) and etc .

Sample Graph
 

Analysis Questions:

1. What is radioactive decay? 

2. Define half- life.

3. If you shake 300 chips, on average how many white surfaces would expect?

4. How many tosses did it take to get rid of all of you chips?

5. Examine the graph, is the rate of the number of white surfaces produced over time linear or nonlinear?  Is the rate constant over time or does it change?

6. Cs-137 has a half-life of 30 years.  Using what you learned about half- life from table approximately, how many years have passed if you have 19 grams of your 300 grams?

7. If 150 years have passed, how much of the original 300 grams sample should be left?

8. Carbon-14 has a half-life of 5730 years.  If you start with 100 grams of carbon-14 in how many years will you have only 50 grams left?

9. In what way is the chip toss like decay of radioactive element?

10. Why is Carbon-14 not used for dating rocks and minerals?

11. If a piece of wood only contains one-eighth of its original Carbon-14, approximately how old is that piece of wood?
     

Balancing Nuclear Equations

Directions:  Predict the products of the following nuclear equations.

Sample: atomic mass number - top number
               atomic number - bottom number               

                          N    +   He

                      Nitrogen-14   +   alpha particle

• Add  the atomic masses of nitrogen -14 and the alpha particle.
                           14 + 4= 18         New mass number

• Next, add the atomic number of nitrogen-14 and the alpha particle.
                           7   + 2= 9

•      Looking at a periodic table, which element has an atomic number of 9.
          Answer: Fluorine

• F      Fluorine -18

Problems:

Alpha decay:   

U  +     He

Beta decay:

 Cu +  _e

_Positron:

Ag +  _e

Electron Capture:

Na + e

Assessment: Pre-Lab Discussion, Group/ Cooperative Learning Rubric, and Responses to Lab Activity Questions.

Illinois State Assessments and Evaluation

IV- C.   apply multiple methods of evaluation to determine student's appropriate use of technology resources for learning, communication, and productivity

Enrichment Activities:

Option 1: 

Choose one of three types of radiation alpha, beta, or gamma.  Make a poster that illustrates the harmful effect to specific organs of the human body.  Find out how  nuclear workers minimize their exposure to radiation.  Include information  about how the Nuclear Regulatory Commission (NRC) monitors exposure rates for individuals that work with radioactive materials.

Option 2:

Write a research paper ( 3-5 pages) that critiques the accuracy of radioactive dating of materials.  Find information on the
internet that disagrees with the theory of an old earth.  Use that information to defend the theory of a young earth.

Option 3:

The United States is depleting its natural resources of coal and oil rapidly.  Scientist believe that by the year 2040
all reserves will be exhausted.  You have been elected as a senator for the state of Illinois.  Legislators and businessmen
have been lobbying for your vote to build more nuclear power plants to supply the demand for energy.  Write a two-page
report describing the  advantages and disadvantages posed by building another nuclear power plant in your state.

Answers to Lab Activity:

1. Radioactive decay is the spontaneous disintegration of a nucleus into a slightly lighter nucleus, in which a radioactive particles and electromagnetic radiation are emitted.
2. Half-life- the time required for half of the atoms of a radioactive nuclide to decay.
3. 1/2
4. 9-10
5. non-linear; yes the rate is constant over time.
6. 120 years
7. approximately 10 grams
8. 5,730 years
9. The chip toss represents the half-life of an atom.
10. Carbon-14 is used to date living things or once living.  Carbon is found in all forms of life.
11. 11,460 years

Answer to Balancing Nuclear Equations:

Alpha:   Th

Beta:   Ni

Positron:  Pd

Electron Capture: Na

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