Forensics Quiz 5

Glass+Chemistry to Soil

Matter

Anything that has a mass and occupies space

Elements

The simplest substance known that provides the building block from which all matter is composed

Atom

The smallest particle of an element that can exist and still retain its identity of that element

Compound

When two or more elements combine to form a new material that’s physically and chemically different from its elemental components

Physical property

The behavior of a substance without chemical reactions; mass, volume, color, texture, boiling and melting point

Chemical property

The behavior of a substance when it undergoes chemical reactions; potential to undergo a specific chemical change or reaction to form a new substance

Physical change

A change in the size, shape, or form of matter with no change in internal makeup of the substance

Chemical change

A change in internal makeup of the substance which cannot be undone, such as burning, cooking, rotting, rusting.

Soda lime glass

Oxide glass composed of sand (silicon oxides) mixed with various metal oxides (soda, sodium carbonate; added to the chemical mixture of glass when they make it to lower the melting point and make it easier to work with; lime, calcium oxide; added to prevent the glass from dissolving in water).

Tempered glass

Strengthened and heat-resistant by introducing it to a stress process of rapid heating and cooling. Used in car windows and laptop screens.

Laminated glass

a piece of plastic sandwiched between two planes of glass. Used in buildings, windows, doors, in homes. Sound attenuation.

Density

Mass/Volume

Major compositions of metals are identified by

spectrophotometry

Trace elements/fingerprints are identified by

neutron activation analysis. They bombard that piece of metal with neutrons and measure the energy of gamma rays emitted. Each metal element on the periodic table has its own signature level of energy of gamma rays emitted.

Paint

a type of coating designed to cover a surface for the purposes of color and/or protection

Binder

Binds the ingredients in paint together, includes delusterants and drying agents.

Shellac

A coating made from an insect extract that protects wood

Varnish

A solution of film formers and resins in an alcohol-based solvent that protects wood

Stain

Contains dyes, colors the wood but does not protect it

Automotive paint

Car paint. The most important type of paint in forensics work

Structural paint

Used in buildings, houses, and walls

Artistic paint

The oldest kind of paint, made with natural pigments for paintings and arto

Other special purpose paints

Paints that don’t fit into any other category, such as those used to color and seal concrete floors, fluorescent for road markings, or skid-resistant paint for foot traffic.

Chip or flake paint evidence

Typically retain all or multiple individual layers of the paint system

Smear paint evidence

Paint is smeared in streak marks left behind, making it a less clean analysis

Analysis of paint’s physical properties

Can analyze the color layered sequence using microspectrophotometry

Analysis of paint’s chemical properties

Can test for solubility and chromatography

Infrared microspectrophotometry

creates a composite of peaks for all the binders and dyes

Scanning electron microscopy with energy dispersive x-ray analysis

“SEM/EDX”. The only viable method for smear paint.

Soil

crushed rocks and minerals mixed with humus.

Humus

decayed plant and animal matter

Soda in Soda-Lime

Sodium carbonate

Lime in Soda-Lime

Calcium oxide

Soda in Soda-Lime used for

lowering melting point to make the glass easier to work with

Lime in Soda-Lime used for

Preventing the glass from dissolving in water