Warm-Up List 5 features of genuine U.S. Currency that are not found on counterfeit currency.

Warm-Up (Answers) Inscribed security thread Microprinting (ex: “United States of America” along portrait) Off-center portrait Watermark of figure Optically variable ink (green to black)

Chromatography

Chromatography Technique for separating and identifying components of mixtures Determine chemical “fingerprint” of paints, dyes, inks Dissolve dyes in liquid (water, alcohol, oils) and separate using chromatography paper Calculating Rf factors can help determine the composition of substances

Relative Mobility Factor (Rf) solvent front color band A origin 2.1 cm 2.8 cm color band B = Rf Distance ink band traveled Distance solvent traveled 2.1 2.8 0.75

Lab: Chromatography of Ink Scenario: A mysterious note was found on Mrs. Chou’s desk. It was written in black ink. Did someone use her favorite pen (a Uniball) to write the note? Possible pens used: Papermate, Uniball, Sharpie, Pilot Mystery pen = ??? Using alcohol as the solvent and by calculating Rf values, conduct a chromatography experiment to determine the pen used to write the note.

Procedures Use a pencil to draw a line (1.5 cm from the bottom) across the filter paper. Using each of the pens, draw a small dot on the line so that they are evenly spaced across. Use a pencil to label the dots. Place a small amount of alcohol in the bottom of the beaker, just enough to cover the bottom. Put the known and mystery strips of filter paper into the beaker. Wait until the alcohol has traveled almost all the way up the paper. Remove from beaker. Draw a pencil line across the solvent line. Let dry. Calculate Rf values.

Experimental Setup

Data Table Pen Type Band # (bottom to top) Band Color Band migration distance (mm) Solvent Migration Distance (mm) Rf Value (band/ solvent) Pilot A B C Uniball (single) Sharpie PaperMate *Unknown*

Analysis and Conclusions Which pen was the unknown? Describe how you determined the identity of the unknown. Besides alcohol, what other solvents do you think you can use to separate ink pigments? What other applications do you think chromatography be used for?

Video: Crime 360 WHO: Who is involved in the crime scene investigation? Who are the victim(s) and suspect(s)? WHAT: Describe the forensic evidence that is gathered. WHERE: Where is the crime scene? Where do the CSI’s go during the case? WHEN: Describe the time-frame of events. When does this all take place? HOW: How do the CSI’s go about solving the case? What happens at the end?