Forensic Quiz 5 Flashcards
Compare and Identify Metals
1.Major Composition of Metals:i.d by spectrophotometry
2.Trace Elements that serve as fingerprints in comparing one metal against the other
-neutron activation
-bombard that piece of metal with neutrons then they measure the energy of gamma rays emitted
How do you i.d
I.d substance by there selective absorption of different wave lengths of light
paint
a type of coating designed to cover a surface for the purpose of imparting color and for protection
Major Chemical Components of Paint
a binder(additives, drying agent,delusterant) (dissolved in solvents) and 1 or more pigment-inorganic substances
Other Types of Coating(they themselves not paint)
- Shellac
2.Varnish
3.Stains
Shellac
coating made from an insect extract(the lac) dissolved in methyl alcohol(used to protect wood)(don’t give color)
Varnish
a solution of film formers and resin dissolved in solvent(protect wood)(don’t give color)
Stains
contain soluble dyes/pigments in a solvent(it colors the wood but does not protect it)
Types of Paint
1.Automotive Paint
2.Structural Paint
3.Artistic Paint
4.Other special purpose paints
Automotive Paint
most important type of paint in forensic work
Structural Paint
building walls and objects
Artistic Paint
oldest type of paint derived from naturally occurring oils and pigments
Other Special Purpose Paints
-used to color and seal concrete floors
-flourescent paint(road signs)
-skid resistant paint
How are cars painted?
1.Two coats of rust proofing
2.primer
3.topcoat-imports color to the car
4.clear coat-acrylic(or urethane based, no pigments, imparts extra durability and uv resistance
Collection of Paint Evidence(of car)
1.Chip/Flake-contains most or all of the layers of paints(forensically yields most info)
2.Smear(streak marks)
Analysis of Paint
A.Physical Properties-color layer sequence (microspectrphotometer)
B.Chemical Properties
Chemical Properties of Paint
-solubility
-chromatography-analyzing the binders and dyes
-scanning electron microscopy (only viable method for smear paint)with energy dispersive x ray analysis(SEMIEDX)-pigments
soil
crushed rocks and minerals mixed with delayed plant and animal matter(humus)
Comparing soil
1.color
2.size and shape of crushed rocks and minerals
3.ph-acid/base(alkaline) 1-14(ph scale)
4.Density Gradient
5.% of humus-chromotography
6.looking at moisture content(%)
matter
anything that has mass and occupies space
element
simplist substance known provides building blocks where all matter is composed
Periodic Table
grouping elements into specific groups color codes and placed with other similar properties
atom
smallest particle of an element that can exist and still retains its identity
CO2
elements in carbon dioxid:carbon and oxygen)
-1 atoms of carbon and 2 atoms of oxygen
compound
when two or more elements combined to form a new material that is different in its physical and chemical properties from it elemental components
Physical Property of Substance
describes the behavior of substance without the alteration of the substance composition through a chemical reaction
ex.color volume mass boiling point texture and melting point
Physical Change of a Substance
-this does not change the makeup of mater(not chemical identity
-change in size, form of matter,shape
Chemical Property
describes the behavior of a substance when its reacts or combines with other substance to form a new substance
Chemical Change
change in substance in there internal makeup it is not easily reversed back to original substance/formex burning/rusting/rotting
States of Matter/Process
- Solid to convert to liquid it melts
2.Liquid to covert to gas it is vaporization
3.Gas to convert Plasma through ionization
Solid
a definite shape/size/dimensions that can be measured, rigid not easily change, molecular bonding is strong
liquid
definite volume, no definite shape, takes form of a container, bonding of molecules glide and slide, gives state of matter fluidity(not rigid)
Gas
no definite volume of shape
Plasma
very hot
Glass Composition
composed of sand(silicon oxides) mixed with various metal oxides
Mixed Metal oxides
1.soda(sodium carbonate)-added to mixture to lower melting point
2.lime(calcium dioxide)-addes to prevent the glass from dissolving in water
Types of oxide glass
1.Soda Lime Glass
2.Tempered Glass(when breaking becomes fragment does not shatter
3.laminated glass(ex.buildings like skyscrapers) provides strength and sound insulatuin
Important Physical Properties for Forensic Characterization of Glass
1.Reflection Index=velocity of light(air)/velocity of light(medium)
2.Density=mass(g)/volume(mL)
3.Types pf Glass
4.Fraction Feature of Glass(can speculate series of impacts
