ch. 5 forensics test; glass

phase

a uniform body of matter; different phases are separated by definite visible boundaries

which characteristic of glass does not belong; age, color, shape, chemical composition

age

plain glass has no regularity in the arrangement of its molecular constituent

amorphous

refractive index measures the speed of light in a vacuum to its speed in

any given substance

define matter

anything that has mass and occupies space

matter

anything that has mass and takes up space

in the immersion method of detecting glass refractive indexes you look for this

becke lines

this type of glass contains boron and has a trade mark named pyrex

borosilicate

how is the mass of an object determined

by comparing it against the known mass of standard objects

what property distinguishes different types of electromagnetic radiation from one another

by their frequency

if density of a solid is greater than the liquid medium in which it is immersed, the object will

sink

liquid glass is floated on molten tin, used in windows and cups and is very common is

soda-lime

what kind of glass is used commonly in bottles and windows

soda-lime glass

name the three states of matter

solid, liquid and gas.

safety glass, breaks into small squares, heated and cooled over and over it

tempered

what is the smallest particle of an element that can exist and still retain its identity

the atom

atom

the basic unit of a chemical element; not divisible by ordinary chemical means

a bright halo that is observed near the border of a particle immersed in a liquid of a different refractive index is known as

the becke line

refraction

the bending of a wave as it passes at an angle from one medium to another

what is refraction

the bending of light waves because of change in velocity

what is a phase

a uniform body of matter distinguished from other matter by definite visible boundaries

becke line

a bright halo that is observed near the border of a particle immersed in a liquid of a different refractive index

what is sublimation

a change of state from a solid to a gas

periodic table

a chart of the elements arranged in a systematic fashion. elements in a given group have similar properties

physical state

a condition or stage in the form of matter; solid, liquid or gas

radial fracture

a crack in a glass that extends outward like the spoke of a wheel form the point at which the glass was struck

concentric fracture

a crack in a glass that forms a rough circle around the point of impact

birefringence

a difference in the two indices of refraction exhibited by most crystalline materials

element

a fundamental particle of matter that cannot be broken down into simpler substances by chemical means

define element

a fundamental particle of matter that cannot be broken into simpler substances by chemical means

temperature

a measure of heat intensity, or the amount of heat in a substance

mass

a measure of how much matter is in an object

what is flotation

a method for measuring the density of glass

what is the smallest unit of a compound

a molecule

sublimation

a physical change from the solid state directly into the gaseous state; ex. dry ice sublimes into carbon dioxide gas

what is the difference between a physical property and a chemical property

a physical property describes a substance without reference to any other substance. A chemical property describes the behavior of a substance when it reacts or combines with another substance

density

a physical property of matter that is equivalent to the mass per unit of volume of a substance

weight

a property of matter that depends on both the mass of a substance and the effects of gravity on that mass

intensive property

a property that is NOT dependent on the size on an object

what is a compound

a pure substance composed of two or more elements

compound

a pure substance made of two or more elements chemically combined

physical property

a quality or condition of a substance that can be observed or measured without changing the substance's composition

photon

a small packet of electromagnetic radiation energy. each one contains a unit of energy equal to the product of Planck's constant and the frequency of radiation: E = hv, where E is energy in Joules, h is Planck's constant and v is the greek letter, nu, for frequency

crystalline solid

a solid that is made up of crystals in which particles are arranged in a regular, repeating pattern

how does flotation work

a standard/reference glass particle is immersed in a liquid whose composition is carefully adjusted until the object remains suspended in the liquid, glass chips of approximately the same size and shape are added to the liquid for comparison. If both the unknown and the standard/reference particles remain suspended in the liquid, their densities are equal to each other and to that of the liquid. Particles of different densities will either sink or float, depending on whether they are more or less dense than the liquid

liquid

a state of matter in which molecules are in contact with one another, but are not rigidly held in place

gas (vapor)

a state of matter in which the attractive forces between molecules are small enough to permit them to move with complete freedom

solid

a state of matter in which the molecules are held closely together in a rigid state

how is color related to the behavior of light

color is a visual indication of the fact that objects absorb certain portions of visible light and transmit or reflect others

what is laminated glass

created by sanwhiching one layer of plastic between two pieces of ordinary window glass

what physical properties are used most often to characterize glass particles

density and refractive index

amorphous solid

describes a solid that lacks an ordered internal structure; denotes a random arrangement of atoms

chemical property

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

how is dispersion related to wavelength and frequency

each color corresponds to a different range of frequencies or wavelengths of light, light rays of one color bend to a different degree than rays of all other colors

visible light

electromagnetic radiation that can be seem with the unaided eye; detected as colored light ranging from red to violet in the electromagnetic spectrum

how are elements and matter related

elements provide the building blocks from which all matter is composed

what are the two most common temperature scales

fahrenheit and celsius

true or false: a significant difference in either density or refractive index proves that the glasses examined have a common origin

false

this laboratory method for identifying glass attempts to determine the density of the glass

floatation method

how did soda-lime glass acquire its name

from the fact that soda and lime are added to the glass to make it easier to work and to prevent it from dissolving in water

what is tempered glass

glass made stronger by introducing stress through rapid heating and cooling of the glass surfaces

tempered glass

glass that is strengthened by introducing stress through rapid heating and cooling of the glass surfaces

x-ray

high-energy, short wavelength form of electromagnetic radiation that can penetrate most solid matter and present the image on photographic film

if you find a piece of glass that fits exactly into the source, it is ______ type of evidence

individual

the composition of basic glass does not include

iron

what happens when tempered glass breaks

it does not shatter, but rather fragments or "dices" into small squares with little splintering.

regular glass is called soda-lime glass but also float glass because

it is floated on molten tin

tempered glass is strong and is also called safety glass because

it shatters into small non-sharp pieces

this type of glass is used for car windshields

laminate

how does weight differ from mass

mass is a constant property of matter that reflects the amount of material present, the mass of an object remains the same everywhere, while weight can vary depending on the force of gravity at a particular location

what is the formula for calculating the density of an object

mass per unit volume (M x V)

what is an example of a two-phase system

oil floating on water

which of the following is NOT a physical state of matter

plasma

glass ID method - uses glass immersed in liquids with known refractive indices

refractive/immersion method

what is the main ingredient in ordinary glass

sand

wavelength

the distance between crests of adjacent waves

wavelength is

the distance between crests of adjacent waves

electromagnetic spectrum

the entire range of radiation energy from the most energetic cosmic rays to the least energetic radio waves

three devices used for comparing the masses different objects

the equal-arm balance, the top-loading balance, the single-pan analytical balance

what is weight

the force with which gravity attracts a body

frequency

the number of complete waves that pass a given point in a certain amount of time

define dispersion

the process of separating light into component colors

refractive index

the ration of the speed of light in a vacuum to its speed in a given substance

dispersion

the separation of light into its component wavelengths

what chemical property determines its state

the strength of the attractive forces between its molecules

celsius scale

the temperature scale on which water freezes at 0 degrees and boils at 100 degrees, with 100 equal divisions or degrees between

farenheit scale

the temperature scale on which water freezes at 32 degrees and boils at 212 degrees, with 180 equal divisions or degrees between

what is the main drawback of using these properties to characterize glass (density and refractive index)

they are class characteristics and individualizing glass to a common source

how do forensic scientists use the knowledge of light behavior

they have learned to characterize different chemical substances by the type of quantity of light they absorb

how does a forensic scientist determine the refractive indices of suspect glass fragments

they use a process called immersion, in which glass particles are immersed in a liquid medium whose refractive index is adjusted by varying its temperature until it equals that of the glass particles. At this point, known as the match point, the observer notes the glass will seem to disappear from view or will be at minimum contrast with the liquid it is immersed in. also, the observer will note the disappearance of the becke line at the match point

what is the only way to individualize glass fragments found at a crime scene to a single source

to assemble the fragment and physically fit them together like a jigsaw puzzle

true or false: a high-velocity projectile, such as a bullet, will often leave a round, crater-shaped that is surrounded by a nearly symmetrical pattern of radial and concentric cracks

true

true or false: the "3R rule" states that "radial cracks form a right angle on the reverse side of the force"

true

true or false: the physical properties of density and refractive index are used most successfully for characterizing glass particles

true

true or false: visible light is only a small part of a large family of radiation that lies outside the electromagnetic spectrum

true

laminated glass

two sheets of ordinary glass bonded together with a plastic film

what part of the car is tempered glass used in

used in side and rear windows

three common compounds

water, carbon dioxide and salt

how might a forensic scientists tell which two fractures on a piece of glass created earlier

when there have been successive penetrations of glass, it is frequently possible to determine the sequence of impact by observing the existing fracture line and their points of termination. a fracture always terminates at an existing line of fracture

what part of the car is laminated glassed used in

windshields