Super Glue Fuming of Latent Fingerprints

Lance Pearson

Number of Learners: 90 Students

Date: 03/04/05

Grade (or Age): 8th grade

School/Town: Timilty Middle/Roxbury

Actual Length of Lesson: 45 minutes

Curriculum Area: Science (Chemistry)

PREREQUISITE KNOWLEDGE AND SKILLS

Students have an understanding that matter can exist in different states (solid, liquid and gases) and that the matter can change between them when the amount of energy (heat) is altered.  

CONTENT TO BE TAUGHT

This lesson plan is best used as a way to boost excitement about science generally and to see how the things they are learning can be applied to real-life problems.  The principal curricular component is to re-enforce the concepts of evaporation, exothermal chemical reactions and chemical bonding. 

RATIONALE

Frequently students see the scientific concepts that they learn as interesting but not particularly useful for them thus removing the principal reason to learn sciences (i.e. to do something useful with the world around you). This lesson plan is designed to show how some simple scientific concepts discussed in class can be combined with simple household chemicals and a little know-how to help real-life crime scene investigators do their job. This guided-inquiry lesson plan ties together the concepts of evaporation, exothermic chemical reactions and chemical bonding and gives a brief look into the more advanced topic of polymerization (and polymers). In so doing, it fulfills at least one of the Massachusetts Frameworks Physical Science (Chemistry), Grades 6–8 curriculum standards: 14. Recognize that heat is a form of energy and that temperature change results from adding or taking away heat from a system.

GOALS

  • Students will observe a supervised demonstration of the process that real-life crime scene investigators sometimes use to identify latent (i.e. no visible with the naked eye) fingerprints.
  • Students will use the scientific concepts that they used to brainstorm ways to improve the process they just witnessed.
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    PERFORMANCE OBJECTIVES

  • Each student will be required to use the physical properties of the super glue to propose how it may be exploited to reveal latent fingerprints. 
  • Each student, after observing the process, will be required to propose ways to improve the process and understand what improving the process would consist of.

    • MATERIALS

    PROCEDURE

    Prep time should consist of making the Lye (NaOH) solution then dipping the cotton balls in the solution to moisten.  Be careful not to get the Lye on your hands (rubber or nylon gloves recommended, absolutely not cotton).  Let the cotton balls dry out, perhaps overnight for use in the demonstration..

    A. Opener
  • Begin with an open-response question session probing student understanding of evaporation, bonding, exothermic (heat releasing; exit) and endothermic (heat capturing; intake) reactions and chemical compounds.  Example questioning is provided in the Appendices.
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  • Explain that a scientific demonstration is going to be conducted and that the safety rules must be followed at all times and take them through those rules (Appendices).
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    B. Development

  • Place object and aluminum foil (with cotton ball on foil) in bottom of a small container

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  • Place 10 drops (for a small container; more for a large container) of superglue on cotton ball

  • Seal the container.

  • Wait for the fingerprint to develop (should take 30 minutes for a small container).  Simply go through the closing as you wait and have the kids examine the results at the end.

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    C. Closing
  • Present some of the chemical properties of super glue (and fingerprints) and ask for brainstorming about how they may be used to accomplish the task of making hidden (clear) fingerprints visible.  Provided in the Appendices.
  • Go over the concept of evaporation and exothermic reactions, both of which are used in conjunction to speed up the super glue evaporation process.
  • Discuss how super glue works by bonding with water to polymerize (to make chemical bonds with other super glue molecules forming long strong chains).
  • As the fingerprints begin to reveal themselves inquire as the how the process could be improved by real scientists and what would be an example of ways to improve it.

  • Cleanup:

    Use acetone (put some on a cotton ball) to clean the super glue from the insides of the container (and/or object); then wash it with water.  Do not use anything for any other purpose until it has been thoroughly cleaned (this includes your hands).

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    EVALUATION

    The quality of the students' proposals as to ways to improve the process that was observed, understanding of what constitutes improvement, and ability to preliminarily propose ways to use the chemical properties of super glue to accomplish the task allows for insight into student understanding of all of the concepts addressed by the lesson plan.

    EXTENSION

    Additional video of some of the other methods of latent fingerprint extraction and other forms of evidence detection such as dusting can be acquired from most episodes of the C.S.I. series on television. Students can be asked to watch footage of this popular show and explain at least few ways that the scientist on the show used the science concepts learned in class.  Students could also be required to present their finding to the class.

    REFERENCES

    http://voh.chem.ucla.edu/vohtar/spring00/30H/pdf/Brubaker.pdf
     
    http://www.brazoria-county.com/sheriff/id/fingerprints/id~superglue.htm

    ASSOCIATED APPENDICES

    Appendices for Fingerprinting Lesson Plan