Properties of Matter and the Analysis of Glass Objectives: Define physical and chemical properties. List and define the metric system’s basic units and prefixes. Compare metric and English units: length, volume, and mass. Define elements and compounds and give examples of each. State the differences between a solid, liquid, and gas. Define phase. State the differences between the wave and particle theories of light. Describe the dispersion of light through a prism. Describe the electromagnetic spectrum. Explain the relationship between color and the selective absorption of light by molecules. Updated 7/6/2019 Created by C. Ippolito August 2007

Properties of Matter and the Analysis of Glass Objectives: Distinguish between the Celsius and Fahrenheit temperature scales. Distinguish mass from weight. Define density. Determine the density of irregular-shaped objects. Define refractive index. Distinguish crystalline from amorphous solids. Define double refraction and birefringence. Describe the flotation and immersion methods for comparing glass specimens. State how to examine glass fractures to determine the direction of impact for a projectile. Describe the proper collection of glass evidence. dec 5 odd 3 Updated 7/6/2019 Created by C. Ippolito August 2007

Created by C. Ippolito August 2007 Properties of Matter Physical Properties describe a substance without reference to any other substance weight volume color Chemical Properties describes the behavior of a substance in the presence of another substance boiling point melting point Updated 7/6/2019 Created by C. Ippolito August 2007

Measuring with SI Units The International System of Units (SI) is a revised version of the metric system dec 5 odd 1 Updated 7/6/2019 Created by C. Ippolito August 2007 4

Created by C. Ippolito August 2007 Metric Prefixes are used to increase or decrease base units to a size appropriate for the measurement undertaken Updated 7/6/2019 Created by C. Ippolito August 2007 5

Created by C. Ippolito August 2007 Metric Units of Length even 4 11/28 Updated 7/6/2019 Created by C. Ippolito August 2007 6

Created by C. Ippolito August 2007 Metric Units of Volume Updated 7/6/2019 Created by C. Ippolito August 2007 7

Created by C. Ippolito August 2007 Metric Units of Mass Weight – force that measures the pull of gravity on a given mass Updated 7/6/2019 Created by C. Ippolito August 2007 8

Metric Units of Temperature measure of how hot or cold an object is Celsius Scale 100 equal intervals between freezing (0°C) and boiling (100°C) points of water Fahrenheit Scale 1°F is 1/180 change from freezing to boiling freezing (32°F) and boiling (212°F) points of water Conversion: °C = (5/9) x (°F-32) °F = (1.8 x °C)+32 Updated 7/6/2019 Created by C. Ippolito August 2007 9

Created by C. Ippolito August 2007 Nature of Matter Matter anything that has mass and occupies space Element matter that cannot be broken down into simpler substances by chemical means Atom – smallest particle of an element still exhibiting its properties Compound matter that can be broken down into simpler substances by chemical means Molecule – smallest particle of a compound still exhibiting its properties Periodic Table systematic arrangement of elements by atomic number Family – vertical column Series – horizontal row Updated 7/6/2019 Created by C. Ippolito August 2007

Created by C. Ippolito August 2007 States of Matter Solid definite shape definite volume particles close together almost incompressible Liquid indefinite shape particles less close together – “flow” Gas indefinite volume particles separated compressible Updated 7/6/2019 Created by C. Ippolito August 2007 11

Created by C. Ippolito August 2007 Changes of State Freezing/Melting Point freeze change from liquid to solid melt change from solid to liquid Boiling/Condensation Point boil change from liquid to gas condense change from gas to liquid Sublimation change from solid directly to gas without passing through liquid state dec 6 even 4 Dec 7 ODD 1 Updated 7/6/2019 Created by C. Ippolito August 2007

Created by C. Ippolito August 2007 Theory of Light Wave Theory of Light Amplitude height from zero to the crest Wavelength (λ) distance between crests SI unit is nanometer Frequency (ν) number of wave cycles passing a given point per unit time SI unit is cycles/sec (cps) or hertz (hz) Wavelength and frequency are inversely proportional F = c/λ Updated 7/6/2019 Created by C. Ippolito August 2007

Created by C. Ippolito August 2007 Behavior of Light Dispersion process of separating light into its component colors Refraction bending of light as its velocity changes when moving from one medium to another (i.e. air to glass, air to water) Updated 7/6/2019 Created by C. Ippolito August 2007

Electromagnetic Spectrum Visible Light small part of all “wave” forms of energy distinguished by wavelengths dec 12 EVEN 4 Updated 7/6/2019 Created by C. Ippolito August 2007

Created by C. Ippolito August 2007 Light as Particles DeBroglie hypothesized that waves could act as both particles and waves at different times Photon discrete package (particle) of light energy amount of energy depends on frequency E = hf h is Planck constant Updated 7/6/2019 Created by C. Ippolito August 2007

Physical Properties of Matter Temperature amount of heat in a substance Extensive Properties – change with amount of object Weight force of gravity on an object Mass amount of matter an object contains Intensive Properties – same regardless of amount of object Density mass per unit volume Refractive Index ratio of velocity of light in a vacuum to its velocity in another medium Updated 7/6/2019 Created by C. Ippolito August 2007

Created by C. Ippolito August 2007 Types of Solids Crystalline Solids substances whose atoms are arranged in definite geometric patterns Double Refraction light refracts into two different beams when crystal does not have cubic configuration Birefringence – difference between the two refractive indexes Amorphous Solids substances whose atoms are arranged in random or disordered positions glass is actually a “liquid” Updated 7/6/2019 Created by C. Ippolito August 2007

Forensic Analysis of Glass Glass particles can connect a criminal to a crime (Locard’s Principle) glass from window glass from headlights glass from windshield glass from dinnerware Updated 7/6/2019 Created by C. Ippolito August 2007

Created by C. Ippolito August 2007 Composition of Glass Sand + metal oxides melted then cooled to form amorphous solid Float Glass bottle and window glass a.k.a. soda (Na2CO3) lime (CaO) glass Borosilicate Glass headlights and heat resistant glass (Pyrex) boron oxide added Tempered Glass side and rear car windows – will not shatter special heating/cooling process Laminated Glass car windshield two glass layers sandwich a layer of plastic images from www.media.mit.edu, mosaik.wordpress.com, www.glass-hl.com Updated 7/6/2019 Created by C. Ippolito August 2007

Comparing Glass Fragments Most glass cannot be individualized using today’s technology based on composition Physical properties can be used as “class characteristics”: density refractive index Updated 7/6/2019 Created by C. Ippolito August 2007

Measuring and Comparing Glass Densities Flotation Method standard/reference glass particle immersed in liquid bromoform or bromobenzene added until glass remains suspended nonstandard particles of similar size and shape added if suspended density same as standard sink density greater/float density less sheet glass can vary by as much as 0.003g/ml but this method can distinguish differences of up to 0.001 g/ml so samples likely from same source if density matches Updated 7/6/2019 Created by C. Ippolito August 2007

Determining and Comparing Refractive Indices Immersion Method glass particles in liquid medium adjusted by temperature change until its refractive index is equal to that of the glass particle determined when Becke line disappears Becke line halo seen around glass particle when in a liquid with a different refractive index from it’s own moves toward medium with higher refractive index GRIM 3 automated system uses computer/video system images from www.gwu.edu/~forchem/BeckeLine/BeckeLinePage.htm Updated 7/6/2019 Created by C. Ippolito August 2007

Classification of Glass Samples FBI lab has tabulated density and refractive indices of all glass samples calculated “distribution” of refractive indices can correlate data to this to find probability of glass coming from same source Updated 7/6/2019 Created by C. Ippolito August 2007

Created by C. Ippolito August 2007 Glass Fractures Radial Fracture cracks in glass that extend out like spokes of a wheel extend from point of impact break on side opposite of force Concentric Fracture cracks in glass that form a circle around point of impact break on side where force applied images from: http://www.channel4.com/science/microsites/S/science/images/crack.gif, Updated 7/6/2019 Created by C. Ippolito August 2007

Created by C. Ippolito August 2007 Glass Stress Marks form arches perpendicular to side where crack originated curving until parallel to opposite side Radial perpendicular opposite impact point Concentric perpendicular on side of impact 3R rule Radial cracks form Right angle on Reverse side of force Updated 7/6/2019 Created by C. Ippolito August 2007

Which bullet hole is first? www.unt.edu Updated 7/6/2019 Created by C. Ippolito August 2007