Forensics Chp. 2 Unit 2a

Physical Properties

describes the behavior of a substance without reference to another

ex. weight, volume, color, B.P., M.P.

Chemical Properties

describes the behavior of a substance when it combines with another substance

ex. any chemical, heroin

Matter

anything that has mass and takes up space

Periodic Table

a chart that organizes the known elements

Atom

smallest particle of an element that retains the identity and properties of that element

Element

pure substance made up of one type of atom that cannot be broken down into simpler substances by chemical means

Compound

made of more than one element, pure substance that can be broken down into 2 or more elements by chemical means

Melting

Solid —> Liquid (energy absorbed)

Freezing

Liquid —> Solid (energy released)

Vaporization

liquid —> gas (energy absorbed)

Condensation

gas —> liquid (energy released)

Sublimation

solid —> gas (energy absorbed)

Deposition

gas —> solid (energy released)

Light

described as a continuous wave and a stream of discrete energy particles

Dispersion

the process of separating light into its component colors

Refraction

the bending of light caused by a change in velocity (ex: fish in water)

Glass

a hard, brittle, amorphous solid made of sand mixed with metal oxides

Soda-lime glass

added calcium oxide; used in window and bottle glass, resistant to water

Borosilicates

added boron oxides to make heat resistant glass; headlights, Pyrex

Tempered Glass

rapidly heated then cooled to make glass that breaks into small pieces; used for side and rear windows in cars

Laminated Glass

2 sheets of glass held together with a plastic film windshiedl

How to determine bullet hole sequence?

use termination points of radial fractures to determine bullet hole sequence

How should glass be packaged?

glass fragments should be packaged in a solid container to avoid further breakage/loss of evidence

How to characterize glass?

characterize glass using density and refractive index

ROYGBIV

red, orange, yellow, green, blue, indigo, violet