Estellvenia Sanders

This lesson was created as a part of the SMART website and is hosted by the Illinois Institute of Technology

Criminology is the deep study of why crimes are committed, how the crimes are committed, and gives information about how to solve the crimes. Criminology gives information about how to solve the crimes.  Criminology also describes the mechanics of the mind of the person or persons involved in the crime. Many crimes are solved scientifically and the purpose of this presentation is to introduce this unique topic to your students in an academic as well as fun way.

Michael Smith ahs spent more than three weeks working on his research paper and the day has finally arrived for him to turn the paper in.   Just as he was about to give the paper to the teacher, he noticed something very interesting about it.

THE SUSPENSION:    Someone had something different on one of his papers which changed the information

Michael read the paper again to be sure that what he had just read was incorrect, however, he found that he was correct.  The information had definitely been changed.

THE SUSPECT:          Stan Limkett who had been an enemy of Michael's for a long time                                            

THE CLUE:                Inky finger prints were all over the side of the paper

THE ASSISTANT:   Michael asked his good friend Leon to help him solve this crime.

THE TOOL:             Michael and Leon decided to use invisible ink on the paper to solve the crime.


                                                       QUICK QUIZ

1.     What was the motive for the crime being committed?

2.      Who was the victim?

3.    Is the suspect in the same class or a different class?

4.    Why was the suspect considered the guilty person?

5.     When was the crime discovered?

The purpose of the presentation is inform the students that not only can they have fun learning chemistry, but that chemistry is used in many facets of life including the area of law enforcement.



 CRIME                                                            SOLUTION

CHEMISTRY                                                    FINGERPRINT

CHROMATOGRAPHY                                    CARBON

PHENOLPHTHALEIN                                      EXCESS

ALKALI                                                            MICROSCOPE

DISSOLVE                                                        SOLUTION

INVISIBLE                                                         IMPRINT

I am inserting a link about fingerprinting to assist you in presenting this lesson.

In case you wanted to make your own paper one day you can go to this site.

Stan decided to do a test to determine if the ink on his paper was different from the ink used by the culprit.  He cut a firm piece of 2.5 m. square from a coffee filter and wrote a word near the bottom of the square using a blue ink pen and a black ink pen.

Dip the bottom of the square and dip it into a saucer of water keeping the writing above the water level.  Allow the water to rise to the top of the paper and let the square dry.  The chemicals in the two inks will be carried up the paper by the rising water leaving two different patterns.  This the method called CHROMATOGRAPHY.

Making Invisible Ink

6-8 laxative pills (must contain the chemical phenolphthalein) **an indicator

 (turns pink when mixed with an alkali like liquid detergent)

1 medium sized bowl

1 table spoon

hot water

Soak coating off the pills and place the pills into the bowl

Add five table spoons of hot water, stir until the pills dissolve.  This solution is your invisible ink 

To check it to see if it works:

Dip a thick-shaped pencil into the ink and allow the students to write their own secret messages on a brown envelope.  Continue to dip the pencil into the ink after every letter.  When the ink is dry, write a false message with a pen. 

To read the message, mix four tablespoons of hot water to make a solution.

Then dip a tissue in the solution and dab it over the envelope.  The secret message turns pink.  If this does not happen, start the entire process over. ***Be very careful using the liquid detergent.  Keep it away from the eyes and make sure the students wash their hands when the experiment is completed.

Also, keep all pills and soda out of the reach of young students..


     Leon is asked by Michael to use the invisible ink to get a set of Stan's fingerprints.  He delivers the message to Stan who takes the paper, reads it and then gives it back Leon.  Leon returns to Michael with the paper with the invisible ink on it covered with the fingerprints of Stan and places it in a small plastic bag.



Every time you touch something, regardless to what it is or where it is, you leave a set of finger prints. Leon had Stan touch the paper and then Leon placed the paper into the plastic bag.  Why?  Prints placed on a slightly shining object, such such as a plastic bag, will show up when covered with powder.  In this investigation, you will use carbon powder .

Carbon powder (simple version)

Burn several slices of toast

Scrape the burnt ashes off the toast ( this is the carbon) into a bowl and crush it with the back of a spoon until it is very fine.  You will also need several white plastic bags.  Once the carbon powder is ready, have someone run her /his fingers through the hair then press the fingertips on the white plastic bag.  Sprinkle the carbon powder onto the fingerprints.  Shake the carbon powder off the bag to reveal the prints.  Cover with sticky tape.

Upon completion of the finger printing, Michael was able to prove that Stan, his enemy for many years, was the guilty party.  He was able to confront Stan with his proof and the teacher was then able to discipline Stan for what he had done.

        This is a fun way to investigate different crimes and a fun way for the students to solve crimes at school, at home, and at play.

                                                            ENJOY AND HAPPY INVESTIGATING!!!!!

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