Crime Busters

Piedmont IB SOWorkshop #2

What is required for success

• Chemistry knowledge• Common sense• Logical thinking• memory• Speed !• Work hard!

What you will learn

• Chemistry• Flow charts/problem solving skills

Topics covered

• Powders• Metals (nationals)• Liquids (nationals)• Fibers and plastics• Paper chromatography• Crime Scene Physical Evidence• Evidence analysis

Powders

Able to identify the following powders• Sodium acetate• Sand• Calcium carbonate (powdered

limestone)• Vitamin C (Ascorbic acid)• Table salt• Sugar• Flour

• Cornstarch• Baking soda• Powdered gelatin• Powdered Alka-Seltzer• Yeast• Borax• talc

Metals(Nationals only)

• Aluminum• Iron• Zinc• Magnesium• Copper• tin

Liquids(Nationals only)

Able to identify the following liquids• Lemon juice• Rubbing alcohol• Household ammonia• Water• Vinegar• Hydrogen peroxide

Polymers, hair and fibers

Hair (National)• Human• Dog• Cat

Polymers• PETE• HDPE• Non-expanded

PS• LDPE• PP• PVC

Fibers (national)• Animal• vegetable• synthetic

Paper chromatograph(National)

• To identify ink, juices, and other colored materials

• Easy to do. Compare unknown with known materials

Physical evidence

• Finger prints– Patterns (whorls, loops, arches)– Compare known to unknown

• Irises

Evidence analysis

• Logical thinking• Speed and clarity

How to identify powders• Appearance/physical

properties– Color– Texture– Odor/smell– Density

• Water solubility/pH• Reaction with HCl

– Rate of reaction– Gas formation– Disappearance of insolubles– smell

• Reaction with Iodine• Other characteristics

Example of powder identification

Sodium acetate• Colorless needles or white

powder• Very water soluble• pH = 8.9• Smells like vinegar when

HCl is added, no other visible reactions

pH of aqueous solution Crystal form Powder form Water solubility 1 M HCl Iodine reagent Other CharacteristicsAnhydrous sodium acetate 8.9 very soluble vinegar smell

How to identify Metals• Appearance/physical properties

– Color– Is it shiny?– Density– Attraction by magnet

• Reaction with HCl– Rate of reaction– Gas formation– Heat generation

How to identify liquids

• Smell• Clarity• pH

How to identify hair

• Microscope• Visual observation

How to identify fibers- only required to distinguish between animal, natural, and synthetic

• Physical properties– Diameter of fiber– Is it straight or curled?– Is it stretchy?– Micrographs provided

• Burning observations (provided)

How to identify plastics

• Appearance– Color– Clarity– Density, using solutions of known density

• Burning properties

Paper chromatography

• Separation of colors (possibly)

• Relative position of spots

• Used to identify the source of ink, juice, and other colored materials

Finger prints

• Remember the different patterns– Whorls– Loops– Arches

• Compare unknown with knowns– Could be partial prints– Know where to look at

DNA

• Similar to paper chromatography in principle, but uses high tech to look at DNA patterns

• Compare known with unknown• Use common sense

Shoeprints and tire treads

• Patterns• Speed and direction of travel

Irises

• Unique like finger print• Some EU countries started using Iris scan