glass and soil physical vs. chemical properties physical properties: describes substances without...

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Glass and Glass and Soil Soil

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Page 1: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Glass and SoilGlass and Soil

Page 2: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Physical vs. Chemical PropertiesPhysical vs. Chemical Properties

Physical properties:Physical properties: describes describes substances without reference to other substances without reference to other substances.substances.– Mass, density, color, weight, volume, Mass, density, color, weight, volume,

boiling point, and melting pointboiling point, and melting point

Page 3: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Physical vs. Chemical PropertiesPhysical vs. Chemical Properties

Chemical propertiesChemical properties:: describes the describes the behavior of substances when it reacts or behavior of substances when it reacts or combines with another substance.combines with another substance.– Ex. Wood burning, Oxidation, reaction to Ex. Wood burning, Oxidation, reaction to

indicatorsindicators• Starch: iodine, Starch: iodine, brown brown purplish black purplish black

• Heroin: Marquis reagent, Heroin: Marquis reagent, turns purpleturns purple

Page 4: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Properties AssessmentProperties Assessment

The property we choose to observe and The property we choose to observe and measure will depend on the type of material measure will depend on the type of material that is being examined. that is being examined.

Properties must:Properties must:– be assigned a numerical valuebe assigned a numerical value

– Relate to a standard system of measurement Relate to a standard system of measurement accepted throughout the scientific communityaccepted throughout the scientific community

Page 5: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Physical Properties: TemperaturePhysical Properties: Temperature

Melting and boiling point.Melting and boiling point.Temperature: the measure of heat Temperature: the measure of heat

intensityintensity–Fahrenheit Fahrenheit

–3232oo F freezing point, 212 F freezing point, 212oo F Boiling point F Boiling point

–Celsius Celsius (centigrade)(centigrade)–00oo C freezing point, 100 C freezing point, 100oo C Boiling point C Boiling point

Page 6: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

TemperatureTemperature

Celsius

(00oo C) C)

Fahrenheit

((oo F) F)

freezing pointfreezing point 0 32

Boiling pointBoiling point 100 212

Body Body temperaturetemperature

37 98.6

Room Room TemperatureTemperature

23 69

Page 7: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

The relationship of Mass per unit volumeThe relationship of Mass per unit volume

– D=m/vD=m/v

Water at 20Water at 20oo C 0.998g/mL = 1g/1.002 mL C 0.998g/mL = 1g/1.002 mL

NOT dependent on the size of an object.NOT dependent on the size of an object.– Same regardless of the size of the substance.Same regardless of the size of the substance.

– Solids (more dense)Solids (more dense) liquids liquids gases gases

DensityDensity

Page 8: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

The amount of occupied spaceThe amount of occupied space Regular Shaped ObjectsRegular Shaped Objects

=LxWxH (cm3)=LxWxH (cm3) Irregular Shaped ObjectsIrregular Shaped Objects

– Volume of displaced fluid in a graduated Volume of displaced fluid in a graduated cylinder.cylinder.

VolumeVolume

Page 9: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Silver Silver 10.5 (g/mL)10.5 (g/mL) Lead Lead 11.511.5 Window glass Window glass 2.47-2.542.47-2.54 Mercury LiquidMercury Liquid 13.6 13.6 Water at 4 C Water at 4 C 1.001.00 IceIce 0.920.92

Physical Properties: DensityPhysical Properties: Density

Page 10: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

VII. Physical properties of glassVII. Physical properties of glass Refraction:Refraction: the bending of a light the bending of a light

wave as it passes from one medium wave as it passes from one medium to another.(a change in velocity, to another.(a change in velocity, slows down) slows down)

IndexIndex = =

water at 25C =1.333 (1.333 times water at 25C =1.333 (1.333 times faster in a vacuum then in water at faster in a vacuum then in water at that temp.that temp.

velocity of light in vacuum velocity of light in vacuum velocity of light in mediumvelocity of light in medium

Page 11: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Refractive IndexRefractive IndexRatio of speeds in a vacuum vs a mediumRatio of speeds in a vacuum vs a medium

– At a specific temperatureAt a specific temperature

– And Wavelength FrequencyAnd Wavelength Frequency

V of light in VacuumV of light in Vacuum

V of light in mediumV of light in mediumRI=RI=

Page 12: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Refractive IndexRefractive Index Water at 25C =1.333 (1.333 times faster Water at 25C =1.333 (1.333 times faster

in a vacuum then in water at that temp.in a vacuum then in water at that temp.

Dependent on temperature and the Dependent on temperature and the frequency of the wavelength of lightfrequency of the wavelength of light

Sodium D light: STANDARD wavelengthSodium D light: STANDARD wavelength– 589.3 nanometers589.3 nanometers

Page 13: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Refractive IndexRefractive Index

Transparent solids immersed in a Transparent solids immersed in a liquid having a similar RI, light will liquid having a similar RI, light will not be refracted as it passes from not be refracted as it passes from liquidliquidsolid.solid.

Reason why the eye unable to Reason why the eye unable to distinguish between the soliddistinguish between the solidliquid liquid boundary.boundary.

Page 14: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Becke line:Becke line:

http://www.hfni.gsehd.gwu.edu/~forchem/BeckeLine/BeckeLinePage.htm

Page 15: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Becke line:Becke line:

nglass >nmedium nglass < nmedium

                   nmedium  = 1.525                      nglass    = 1.60

                   nmedium = 1.525                    nglass    = 1.34

Page 16: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

List the four major types of List the four major types of glass and describe how they glass and describe how they are made. are made.

Page 17: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Glass ObjectivesGlass Objectives

TypesTypesMatchingMatchingFracturesFracturesPreservationPreservation

Page 18: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Comparing Glass Comparing Glass FragmentsFragmentsComposed of silicon oxides mixed with metal oxidesComposed of silicon oxides mixed with metal oxides

Soda-lime glassSoda-lime glass Soda (NaCo3)Soda (NaCo3)

Lime (CaO)Lime (CaO)

windows windows bottlesbottles

Pyrex Pyrex BorosilicatesBorosilicates

use Boron oxide, use Boron oxide, Can with stand Can with stand HIGH heatsHIGH heats

Test tubesTest tubes

HeadlightsHeadlights

Tempered Glass:Tempered Glass: Rapid heating and Rapid heating and cooling does not cooling does not shattershatter

Shower doorsShower doors

Side + rear Side + rear windowswindows

Laminated GlassLaminated Glass Plastic or Glass and Plastic or Glass and glues and sandwichglues and sandwich

windshieldswindshields

Page 19: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Matching glass fragmentsMatching glass fragments Suspect and crime scene fragments must Suspect and crime scene fragments must

fit together to be from same sourcefit together to be from same source Physical properties of density and Physical properties of density and

refractive index are used most refractive index are used most successfully for characterizing glass successfully for characterizing glass particles.particles.

1.1. Flotation test in density column!! 0.0001Flotation test in density column!! 0.00012.2. Immersion MethodImmersion Method3.3. GRIM 2: Glass RI measurement (GRIM 2: Glass RI measurement (automated)automated)

Page 20: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Flotation test in density Flotation test in density column!!column!!

Control glass added to Control glass added to liquidliquid

Density of liquid Density of liquid adjusted until control adjusted until control glass suspendedglass suspended

Unknown is then added Unknown is then added to see if it floats or sinksto see if it floats or sinks

Page 21: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Matching glass fragments: Matching glass fragments:

Immersion method:Immersion method:– Glass put into liquidGlass put into liquid– RI of liquid adjusted by temperature until a RI of liquid adjusted by temperature until a

match point is reached.match point is reached.•Point when Becke line disappears because Point when Becke line disappears because both liquid and glass have same RI.both liquid and glass have same RI.

Becke line:Becke line: a bright halo that is observed a bright halo that is observed near the border of a particle immersed in near the border of a particle immersed in a liquid of a different RI a liquid of a different RI

Page 22: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Matching glass fragments: Matching glass fragments:

Becke line:Becke line: a bright halo that is a bright halo that is observed near the border of a particle observed near the border of a particle immersed in a liquid of a different RI immersed in a liquid of a different RI

Page 23: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

What If?What If? Density and RI values do not match:Density and RI values do not match:

•Then not from the same sourceThen not from the same source

Density and RI values Match!Density and RI values Match!•Still cannot ID from same source Still cannot ID from same source •Must compare results to frequencies in Must compare results to frequencies in societysociety

•Must develop meaningful assessment as to Must develop meaningful assessment as to probability that fragments were at one time probability that fragments were at one time from one source.from one source.

Page 24: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Glass FracturesGlass Fractures

If the force is greater then glass’s If the force is greater then glass’s elasticity, it fractureselasticity, it fractures

Fractures provide valuable Fractures provide valuable information at the crime scene. information at the crime scene. – Ex: Ex:

•Force Force •DirectionDirection•Object usedObject used

Page 25: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Information ObtainedInformation Obtained Small hole:Small hole: small stone thrown hard, small stone thrown hard,

small bulletsmall bullet

Shattered glass:Shattered glass: close range shot, large close range shot, large stonestone (obvious gunpowder deposits)(obvious gunpowder deposits)

Hole from projectile can determine Hole from projectile can determine directiondirection Hole is wider at exit sideHole is wider at exit side

As projectile decreases irregularity of As projectile decreases irregularity of shape and cracks increaseshape and cracks increase

                                                               

Page 26: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Fracture patterns Fracture patterns

Radial fractures: Radial fractures: cracks extend cracks extend outward like spokes of a wheel outward like spokes of a wheel from point of impactfrom point of impact

Concentric Fractures:Concentric Fractures: forms forms rough circle around point of rough circle around point of impactimpact

Page 27: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,
Page 28: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Glass Fractures Sequence:Glass Fractures Sequence:

Page 29: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Counting the bullet holesCounting the bullet holes

Page 30: Glass and Soil Physical vs. Chemical Properties  Physical properties: describes substances without reference to other substances. –Mass, density, color,

Collecting and preservation of Collecting and preservation of glass evidence.glass evidence. All glass must be found to include odds All glass must be found to include odds

of matching pieces from suspect to of matching pieces from suspect to C.S.C.S.

Must Obtain Controls: suspect, C.S.Must Obtain Controls: suspect, C.S.– Control from area closest to point of Control from area closest to point of

breakbreak– Glass placed in solid containersGlass placed in solid containers– Individually wrap garments from suspect.Individually wrap garments from suspect.

•To be later check for glass fragments!!!To be later check for glass fragments!!!