Glass Fracture Patterns Worksheet Answers

Forensic Drinking glass Analysis Forensic Science

Limerick of Glass • Is a hard, brittle, amorphous material – Called an amorphous solid because its atoms are bundled in a random fashion – Due to its irregular atomic structure, it produces a multifariousness of fracture patterns when broken • Has numerous uses and thousands of compositions Copyright © Texas Pedagogy Agency 2011. All rights reserved. Images and other multimedia content used with permission. 2

Composition of Glass (continued) • Made past melting the following ingredients at extremely high temperatures – Sand • The primary ingredient • Also known as silica or silicon dioxide (Si. O 2) – Lime or calcium oxide (Ca. O) is added to prevent the glass from becoming soluble in water – Sodium oxide (Na 2 O) is added to reduce the melting point of silica or sand Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. three

Composition of Glass (connected) • Three categories of substances institute in all glass – Formers • Makes up the bulk of the glass • Examples: silicon dioxide (Si. O two) in the form of sand, boron trioxide (B 2 O 3), and phosphorus pentoxide (P 2 O five) – Fluxes • Change the temperature at which the formers melt during the manufacturing of drinking glass • Examples: sodium carbonate (Na 2 CO three) and potassium carbonate (K ii CO iii) – Stabilizers • Strengthen the glass and make it resistant to water • Calcium carbonate (Ca. CO three) is the most oftentimes used Copyright © Texas Pedagogy Agency 2011. All rights reserved. Images and other multimedia content used with permission. four

Composition of Drinking glass (continued) • The raw materials for making glass are all oxides – The limerick of whatever sample can be given in terms of the pct of each oxide used to go far – Example: the estimate limerick of window or canteen glass is • • • Silica (Si. O 2) – 73. 6 % Soda (Na 2 O) – 16. 0 % Lime (Ca. O) – 5. 2 % Potash (K 2 O) – 0. 6 % Magnesia (Mg. O) – iii. six % Alumina (Al ii O 3) – one. 0 Copyright © Texas Pedagogy Agency 2011. All rights reserved. Images and other multimedia content used with permission. 5

Types of Glass • Obsidian is a natural form of glass that is created by volcanoes • Soda-lime glass – The almost basic, common, inexpensive glass – also the easiest to make – Used for manufacturing windows and bottle glass Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. half dozen

Types of Glass (connected) • Leaded glass – Contains lead oxide which makes it denser – Sparkles every bit lite passes through information technology (light waves are aptitude) – Used for manufacturing fine glassware and fine art glass – Is commonly called crystal Copyright © Texas Pedagogy Agency 2011. All rights reserved. Images and other multimedia content used with permission. 7

Types of Drinking glass (continued) • Tempered glass – Stronger than ordinary drinking glass – Strengthened past introducing stress through rapid heating and cooling of its surface – When broken, this glass does not shatter, only fragments or breaks into small squares – Used in the side and rear windows of automobiles Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 8

Types of Drinking glass (continued) • Laminated drinking glass – Constructed past bonding ii ordinary sheets of glass together with a plastic film – Also used past automobile manufactures Copyright © Texas Education Bureau 2011. All rights reserved. Images and other multimedia content used with permission. 9

Comparing Glass • Investigation/Analysis includes – Finding – Measuring – Comparison Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 10

Comparison Glass (continued) • Private Characteristics – Just occurs when the suspect and crime scene fragments are assembled and physically fitted together – Comparisons of this type require piecing together irregular edges of broken glass besides as matching all irregularities and striations on the broken surfaces – Almost drinking glass prove is either too fragmentary or minute to permit a comparison of this blazon Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. xi

Comparing Glass (continued) • Class Characteristics (Density and Refractive Index) – The general composition of glass is relatively uniform and offers no individualization – Trace elements in drinking glass may prove to be distinctive and measureable characteristics – The concrete properties of density and refractive index are used most successfully for characterizing drinking glass particles, but merely as a grade feature – This data (density and refractivity) gives analysts the opportunity to compare and exclude different sources of data Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 12

Methods of Comparison: Density and Measurements • Density comparison – A method of matching glass fragments – Density (D) is calculated past dividing the mass (1000) of a substance by its book (5) • D = K / V Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 13

Methods of Comparison: Density and Measurements (continued) • Density comparison (continued) – Example • A solid is weighed on a residuum against known standard gram weights to determine its mass • The solid's volume is then adamant from the volume of water it displaces • Measured past filling a cylinder with a known book of water (v 1), adding the object, and measuring the new water level (v two) • The difference (v two – v ane) in milliliters is equal to the volume of the solid • Density can now be calculated from the equation in grams per milliliter Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 14

Methods of Comparing: Density and Measurements (continued) • Flotation comparison – A sample of glass is dropped into and sinks to the bottom of a liquid containing an exact volume of a dense liquid, such equally bromobenzene (d = 1. 52 thou/m. 50) – A denser liquid, such equally bromoform (d = 2. 89 one thousand/g. L), is added one drop at a time until the piece of glass rises up from the lesser and attains neutral buoyancy – Neutral buoyancy occurs when an object has the verbal same density as the surrounding fluid, and neither sinks nor floats, but is suspended in one place beneath the surface of the fluid Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 15

Methods of Comparing: Density and Measurements (continued) • Flotation comparing (continued) – The same process is then performed with some other piece of glass, and if the book needed to attain neutral buoyancy is the aforementioned as for the first sample, and so the densities of the ii samples are equal – The exact density of each sample can exist calculated by using the following formula: d = X (2. 89) + Y (1. 52) X+Y • 10 and Y refer to the volumes of the respective liquids, with the numbers in parentheses referring to the densities of each liquid Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 16

Methods of Comparison: Refractivity • Refractive Alphabetize – A mensurate of how much an object slows light • Light slows down when it passes through whatever medium (the denser the medium, the slower the light travels) • Whatsoever object that transmits lite has its own refractive alphabetize – A ratio of the velocity of light in a vacuum to the velocity of light in a particular medium (refractive alphabetize = velocity of light in a vacuum / velocity of low-cal in a medium) Copyright © Texas Teaching Agency 2011. All rights reserved. Images and other multimedia content used with permission. 17

Methods of Comparison: Refractivity (continued) • When calorie-free passes through media with unlike refractive indexes – Refraction (bending of the calorie-free) occurs – This is why objects appear bent or distorted underwater – Every liquid has its ain refractive index – If a piece of glass is placed in a liquid with a unlike refractive index an outline of the glass is clearly visible • This line is known as the Becke Line Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 18

Methods of Comparing: Refractivity (continued) • When light passes through a piece of glass placed in a liquid with the aforementioned refractive alphabetize – The glass bends lite at the same angle as the liquid – The Becke Line disappears – The glass seems to disappear Copyright © Texas Education Bureau 2011. All rights reserved. Images and other multimedia content used with permission. nineteen

Drinking glass Fracture Patterns • Glass has a sure degree of elasticity – It breaks when its rubberband limit is exceeded – The elasticity produces fractures when information technology is penetrated by a projectile (i. e. a bullet) Copyright © Texas Education Bureau 2011. All rights reserved. Images and other multimedia content used with permission. 20

Glass Fracture Patterns (continued) • Types of fractures – Radial • Produced get-go • Always form on the side of the glass opposite to where the impact originated • Look like spider webs that spread outward from the impact hole • Always finish into an existing fracture Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 21

Glass Fracture Patterns (continued) • Types of fractures (continued) – Concentric • Form next • Encircle the bullet hole • E'er start on the same side as that of the subversive force Copyright © Texas Instruction Bureau 2011. All rights reserved. Images and other multimedia content used with permission. 22

Glass Fracture Patterns (connected) • Determining the sequence of multiple bullet holes – The radial fractures from the 2nd bullet hole always terminate into the fractures from the first bullet pigsty – The radial fractures from a 3rd bullet terminate into the radial fractures from the 2nd bullet, and and so forth • Determining the showtime shooter – Examine the termination lines of the radial fractures from each bullet pigsty – Compare the size of the exit and entrance holes of each bullet Copyright © Texas Educational activity Agency 2011. All rights reserved. Images and other multimedia content used with permission. 23

Drinking glass Fracture Patterns (continued) • Determining the direction from which a bullet was fired – Compare the size of the entrance pigsty to the size of the leave pigsty • Get out holes – Always larger, regardless of the type of material that was shot – A larger slice of glass is knocked out of the surface where the bullet is leaving because glass is rubberband and bows outward when struck Copyright © Texas Teaching Bureau 2011. All rights reserved. Images and other multimedia content used with permission. 24

Drinking glass Fracture Patterns (connected) • Determining the management from which a bullet was fired – Compare the size of the entrance hole to the size of the exit hole (continued) • Archway holes – The bullet makes a very small hole when it enters – The glass ever blows dorsum in the direction of the impact because of its elasticity – The glass snaps dorsum violently later on beingness stressed and can blow shattered glass back several meters – Most of the shattered glass lands on the impacted side of the glass, instead of by the exit hole Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 25

Collecting Glass as Show • Avoid the loss or contamination of any evidence samples • Identify and photo all glass samples before moving them • Collect the largest fragments • Identify the outside and inside surfaces of whatever glass • Indicate the relative position of multiple window panes in a diagram Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 26

Collecting Drinking glass equally Testify (connected) • Note any other trace show plant on or embedded in the glass, such as skin, hair, claret, or fibers • Package all of the collected materials properly in order to maintain the chain of custody • Separate the drinking glass past physical properties, such every bit size, color, and texture Copyright © Texas Didactics Agency 2011. All rights reserved. Images and other multimedia content used with permission. 27

Collecting Drinking glass as Evidence (continued) • Itemize the samples and keep them separated in order to avert contamination between two different sources • Split the glass fragments from any other trace evidence (eastward. g. , hair, blood, fibers) once in the lab • Examine any wear (or other objects that may have been used to break the drinking glass) related to the crime scene for drinking glass fragments and other trace show Copyright © Texas Didactics Agency 2011. All rights reserved. Images and other multimedia content used with permission. 28

Resources • • Texas Education Bureau, Forensic Certification Training, Sam Houston Country University Forensic Scientific discipline: Fundamentals & Investigation (1 st Edition), Anthony Bertino Forensic Science: From the Crime Scene to the Crime Lab (1 st Edition), Richard Saferstein Chem. Matters, "More than Than Meets The Heart" Brian Rohrig The Science Spot – Forensic Scientific discipline – http: //www. sciencespot. internet/Pages/classforsci. html Investigator/Officer'due south Personal Feel Corning Museum of Glass site – http: //world wide web. cmog. org/default. asp Federal Agency of Investigation: Laboratory Services – Forensic Glass Comparison: Groundwork Information Used in Data Estimation – http: //www. fbi. gov/about-us/lab/forensic-science-communications/fsc/april 2009/review Introduction to Forensic Glass Examination http: //www. fbi. gov/about-us/lab/forensic-sciencecommunications/fsc/jan 2005/standards/2005 standards 4. htm/ – Collection, Handling, and Identification of Glass http: //world wide web. fbi. gov/near-us/lab/forensic-sciencecommunications/fsc/january 2005/standards/2005 standards 5. htm/ – Glass Density Determination http: //world wide web. fbi. gov/near-us/lab/forensic-sciencecommunications/fsc/jan 2005/standards/2005 standards eight. htm/ Copyright © Texas Education Bureau 2011. All rights reserved. Images and other multimedia content used with permission. 29

Glass Fracture Patterns Worksheet Answers,

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