1. Physical Properties: Glass and Soil and Impression Analysis Physical and chemical properties. Physical and chemical properties. Metric and British systems. Metric and British systems. Celsius (Centigrade) vs Fahrenheit. Celsius (Centigrade) vs Fahrenheit. Mass vs weight. Mass vs weight. Density Density Refractive Index Refractive Index Crystalline vs amorphous solids. Crystalline vs amorphous solids. Double refraction and birefringes. Double refraction and birefringes.

2. Dispersion of light through a prism. Dispersion of light through a prism. Flotation and immersion methods for comparing glass specimens. Flotation and immersion methods for comparing glass specimens. Examining glass fractures to determine the direction of impact from a projectile. Examining glass fractures to determine the direction of impact from a projectile. Proper collection of glass evidence. Proper collection of glass evidence. Forensic properties of soil. Forensic properties of soil. Density-gradient tube technique. Density-gradient tube technique. Proper collection of soil evidence. Proper collection of soil evidence. ● Impression analysis

3. Significance of Physical Evidence Identification- determination of the physical or chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit. Identification- determination of the physical or chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit. Identification first requires the adoption of testing procedures that give characteristic results for specific standard materials. (must be repeatable) Identification first requires the adoption of testing procedures that give characteristic results for specific standard materials. (must be repeatable) Second, identification requires that the number and type of tests needed to identify a substance be sufficient to exclude all other substances. For example, if a conclusion is made that a white substance is heroin, then the test results must be comprehensive enough to have excluded all other drugs, or for that matter, all other substance under consideration. Second, identification requires that the number and type of tests needed to identify a substance be sufficient to exclude all other substances. For example, if a conclusion is made that a white substance is heroin, then the test results must be comprehensive enough to have excluded all other drugs, or for that matter, all other substance under consideration. The amount of tests needed to identify a substance varies, it may be just one or it may be 5 or 6. The amount of tests needed to identify a substance varies, it may be just one or it may be 5 or 6. Egg white powder cocaine cocaine

4. Comparison- subjects a suspected specimen and a standard/reference specimen to the same tests and examinations for the ultimate purpose of determining whether or not they have a common origin. Comparison- subjects a suspected specimen and a standard/reference specimen to the same tests and examinations for the ultimate purpose of determining whether or not they have a common origin. Individual characteristics- properties of evidence that can be attributed to a common source with an extremely high degree of certainty. Individual characteristics- properties of evidence that can be attributed to a common source with an extremely high degree of certainty. Cross linking hair found at a crime scene to a suspect. Cross linking hair found at a crime scene to a suspect. Cross linking paint chips on a hit and run victim to a suspected automobile. Cross linking paint chips on a hit and run victim to a suspected automobile. Matching ridge characteristics of two fingerprints Matching ridge characteristics of two fingerprints Comparison or random striation markings on bullets or tool marks Comparison or random striation markings on bullets or tool marks The fitting together of the irregular edges of broken objects in the manner of a jigsaw puzzle. The fitting together of the irregular edges of broken objects in the manner of a jigsaw puzzle. Comparing irregular and random wear patterns in shoe or tire impressions Comparing irregular and random wear patterns in shoe or tire impressions

5. Class (Identified) Characteristics-properties of evidence that can only be associated with a group and never a single source. Class (Identified) Characteristics-properties of evidence that can only be associated with a group and never a single source. ex. Blood groups, type of shoe, type of bullet, etc. Product Rule- multiplying together the frequencies of independently occurring genetic markers to obtain an overall frequency of occurrence for a genetic profile. For the example- 1 in 200 people would have this same blood profile. Product Rule- multiplying together the frequencies of independently occurring genetic markers to obtain an overall frequency of occurrence for a genetic profile. For the example- 1 in 200 people would have this same blood profile.

6. Crime Scene Reconstruction Reconstruction Reconstruction The method used to support a likely sequence of events by the observation and evaluation of physical evidence, as well as statements made by those involved with the incident. The method used to support a likely sequence of events by the observation and evaluation of physical evidence, as well as statements made by those involved with the incident. involves a collaborative effort that includes law enforcement personnel, medical examiners, and criminalists. involves a collaborative effort that includes law enforcement personnel, medical examiners, and criminalists. Was there more than one person involved? How was the victim killed? Were there actions taken to cover up what actually took place? Was there more than one person involved? How was the victim killed? Were there actions taken to cover up what actually took place? Physical evidence left at the crime scene plays a crucial role and is the foundation of a reconstruction. Physical evidence left at the crime scene plays a crucial role and is the foundation of a reconstruction.

7. Law enforcement personnel must enhance all aspects of the crime scene search to optimize the crime scene reconstruction. Law enforcement personnel must enhance all aspects of the crime scene search to optimize the crime scene reconstruction. Using the physical evidence available to the naked eye, he or she can hypothesize about what occurred, where it occurred, and when it occurred. Using the physical evidence available to the naked eye, he or she can hypothesize about what occurred, where it occurred, and when it occurred. The positioning of the victim at the crime scene gives medical examiners pertinent information for the investigation. The positioning of the victim at the crime scene gives medical examiners pertinent information for the investigation. evaluation of livor distribution- Was the body moved? Was the body clothed after death? (Livor will not develop within areas of the body that are restricted by clothing.) evaluation of livor distribution- Was the body moved? Was the body clothed after death? (Livor will not develop within areas of the body that are restricted by clothing.) laser beams can be used to plot the bullet path in trajectory analysis. Location of the shooter relative to the victim can be determined. laser beams can be used to plot the bullet path in trajectory analysis. Location of the shooter relative to the victim can be determined.

8. Sean Bell Case Position of victim is determined. Position of victim is determined.

9. Glass and Soil Properties of Matter Glass and Soil Properties of Matter The distinguishing characteristics of a substance used in its identification & description The distinguishing characteristics of a substance used in its identification & description characteristics by which people are recognized characteristics by which people are recognized hair color, tone of voice, walk, shape of nose hair color, tone of voice, walk, shape of nose chemical substances are recognized by how they look & behave chemical substances are recognized by how they look & behave each chemical substance has a unique set of properties that distinguish it from all other substances each chemical substance has a unique set of properties that distinguish it from all other substances

10. Properties of Matter Chemical Properties Chemical Properties a characteristic of a substance that describes the way the substance undergoes or resists change to form a new substance a characteristic of a substance that describes the way the substance undergoes or resists change to form a new substance Physical Properties Physical Properties a characteristic of a substance that can be observed without changing the substance into another substance a characteristic of a substance that can be observed without changing the substance into another substance

11. Physical Properties Extensive Properties Extensive Properties depend on the amount of sample depend on the amount of sample volume, mass volume, mass Intensive Properties Intensive Properties do not depend on the amount of sample do not depend on the amount of sample melting point, density melting point, density

12. The Metric System- a review Conversions: 1 inch = 2.54 cm 1 meter= 39.37 inches 1 liter= 1.06 quarts 1 kilogram= 2.2 pounds 1 pound = 453.6 grams Prefixes K1000H100Dk10B1D.1C.01M.001

13. Density The ratio of the mass of an object to the volume occupied by that object The ratio of the mass of an object to the volume occupied by that object g/cm 3 (solids); g/mL (liquids) (1cm 3 =1ml in volume) g/cm 3 (solids); g/mL (liquids) (1cm 3 =1ml in volume) d = m/V Densities of solids & liquids are often compared to the density of water Densities of solids & liquids are often compared to the density of water sink or float sink or float Varies with temperature Varies with temperature

14. Temperature Temperature-measure of the heat intensity of Temperature-measure of the heat intensity of an object. Mercury thermometers are used to measure temp. because mercury expands measure temp. because mercury expands when heated to rise up a tube and contracts when heated to rise up a tube and contracts when cooled to lower down the tube. Fahrenheit Scale- temperature scale using Fahrenheit Scale- temperature scale using the melting point of water as 32  and the the melting point of water as 32  and the boiling point of water as 212 , with 180 boiling point of water as 212 , with 180 degrees between. degrees between. Celsius Scale- temperature scale using the melting point of water as 0  and the boiling point of water as 100  with 100 degrees between. Celsius Scale- temperature scale using the melting point of water as 0  and the boiling point of water as 100  with 100 degrees between.

15. Weight vs Mass Weight- measure of the gravitational pull on an object. W= mg Weight- measure of the gravitational pull on an object. W= mg Mass- the amount of matter in an object Mass- the amount of matter in an object

16. Refraction Index- Immersion Method- glass particles are immersed in a liquid medium whose refraction index is varied (by varying the temp. of the liquid) until it is equal to that of the glass particles. At the “match point” there will be the disappearance of the Becke Line (a bright halo that is observed near the border of a particle immersed in a liquid of a different refraction index.) Becke line disappears!!!!! Becke line disappears!!!!!

17. Refraction The bending that occurs when a light wave passes at an angle from one medium to another (air to glass) The bending that occurs when a light wave passes at an angle from one medium to another (air to glass) bending occurs because the velocity of the wave decreases bending occurs because the velocity of the wave decreases

18. Refractive Index (N D ) The ratio of the velocity of light in a vacuum to the velocity of light in a given medium The ratio of the velocity of light in a vacuum to the velocity of light in a given medium N D (water) = 1.333 N D (water) = 1.333 light travels 1.333 time faster in vacuum light travels 1.333 time faster in vacuum than in water Velocity of light in a vacuum Velocity of light in a vacuum Velocity of light in medium Velocity of light in medium An intensive property An intensive property Varies with temperature and the light frequency Varies with temperature and the light frequency When a transparent solid is immersed in a liquid of a similar refractive index light will not be refracted as it passes from the liquid to the solid and the eye will not be able to distinguish the liquid solid boundary. The solid seems to disappear from view. When a transparent solid is immersed in a liquid of a similar refractive index light will not be refracted as it passes from the liquid to the solid and the eye will not be able to distinguish the liquid solid boundary. The solid seems to disappear from view.

20. What is Glass? Glass- hard, brittle amorphous substance composed of silicon oxides mixed with various metal oxides. Glass- hard, brittle amorphous substance composed of silicon oxides mixed with various metal oxides. main ingredient is sand. Heat sand and metal oxides to melting and cool to rigid condition without crystallization= glass! main ingredient is sand. Heat sand and metal oxides to melting and cool to rigid condition without crystallization= glass! Adding soda (Na2CO3) and melting point and viscosity are lowered- easier to work with. Adding soda (Na2CO3) and melting point and viscosity are lowered- easier to work with. Adding lime (CaO) and glass will not dissolve in water. Adding lime (CaO) and glass will not dissolve in water.

21. Structure of Glass

22. What is Glass? An extended, 3D network of atoms which lacks the repeated, orderly arrangement typical of crystalline materials (AMORPHOUS) An extended, 3D network of atoms which lacks the repeated, orderly arrangement typical of crystalline materials (AMORPHOUS) The viscosity is such a high value that the amorphous material acts like a solid The viscosity is such a high value that the amorphous material acts like a solid materials which form glasses are relatively rare materials which form glasses are relatively rare SiO 2 (silica) is the most common example SiO 2 (silica) is the most common example

23. Common types of Glass at Crime Scenes soda-lime glass- window and bottle glass. Common metal oxides in this type of glass are sodium, calcium, magnesium and aluminum. soda-lime glass- window and bottle glass. Common metal oxides in this type of glass are sodium, calcium, magnesium and aluminum. Borosilicates- automobile headlights and heat resistant glass, such as Pyrex. Boron oxide is added to the oxide mix. Borosilicates- automobile headlights and heat resistant glass, such as Pyrex. Boron oxide is added to the oxide mix. Tempered glass- used in making some windshields, side and rear windows of automotives. Made stronger by introducing stress through rapid heating and cooling of glass surfaces Tempered glass- used in making some windshields, side and rear windows of automotives. Made stronger by introducing stress through rapid heating and cooling of glass surfaces Does not shatter upon impact, but breaks into fragments or “dices” into small squares with little splintering. Does not shatter upon impact, but breaks into fragments or “dices” into small squares with little splintering. Laminated glass- used in making windshields of all cars made in the USA. Two sheets of ordinary glass bonded together with a plastic film. Laminated glass- used in making windshields of all cars made in the USA. Two sheets of ordinary glass bonded together with a plastic film.

24. Physical Properties At ordinary temp. At ordinary temp. internal structure resembles a fluid internal structure resembles a fluid random molecular orientation random molecular orientation external structure displays the hardness & rigidity of of a solid external structure displays the hardness & rigidity of of a solid Does not show a distinct melting point Does not show a distinct melting point on heating gradually softens on heating gradually softens on cooling gradually thickens on cooling gradually thickens

25. Glass Fracture Examination Types of Fractures

26. Impact Fractures Impact causes a pane of glass to bulge Side opposite the impact will stretch more & rupture first Radial cracks are rapidly propagated in short segments from the point of impact

27. Impact Fractures If the pane is held firmly on both sides If the pane is held firmly on both sides a circular pattern of cracks (concentric) will form after the radial fractures have formed around point of impact a circular pattern of cracks (concentric) will form after the radial fractures have formed around point of impact

28. Forensic Examination Stress marks on radial cracks can be used to determine on which side of pane impact occurred Stress marks on radial cracks can be used to determine on which side of pane impact occurred To perform examination To perform examination identify one or more pieces which have cracks terminating at a point of impact identify one or more pieces which have cracks terminating at a point of impact fit these pieces onto one or more pieces marked “inside” or “outside” fit these pieces onto one or more pieces marked “inside” or “outside”

29. Three R Rule Radial cracks are at Right angles to the Rear (side opposite the impact)

30. Three R Rule Exceptions Exceptions tempered glass tempered glass “dices” without forming ridges “dices” without forming ridges very small windows held tightly in frame very small windows held tightly in frame can’t bend or bulge appreciably can’t bend or bulge appreciably windows broken by heat or explosion windows broken by heat or explosion no “point of impact” no “point of impact”

32. Fractures Caused by Projectiles High-velocity projectiles High-velocity projectiles crater-like hole surrounded by a nearly symmetrical pattern of radial and concentric cracks crater-like hole surrounded by a nearly symmetrical pattern of radial and concentric cracks Exit hole will be larger than entry hole. Exit hole will be larger than entry hole. the size of the hole & diameter of crater are dependent on the size of the projectile the size of the hole & diameter of crater are dependent on the size of the projectile

33. Fractures Caused by Projectiles

34. Order of bullet holes When 2 bullet holes are found, points of termination of fracture line are determined. A fracture always terminates at an existing line of fracture. When 2 bullet holes are found, points of termination of fracture line are determined. A fracture always terminates at an existing line of fracture.

35. Mechanical Fit In lab glass fragments are compared, linked, pieced together and analyzed to determine exactly what happened at the scene of the crime. Glass possesses its greatest value when crime scene fragments can be assembled and In lab glass fragments are compared, linked, pieced together and analyzed to determine exactly what happened at the scene of the crime. Glass possesses its greatest value when crime scene fragments can be assembled and physically fitted together individualizing it to one source. physically fitted together individualizing it to one source.

36. Glass as Forensic Evidence Glass fragments recovered from clothing Glass fragments recovered from clothing number & distribution are important number & distribution are important a piece of glass embedded in a shoe has low value a piece of glass embedded in a shoe has low value many small fragments from a shirt or sweater can be highly significant many small fragments from a shirt or sweater can be highly significant

37. Classification Tests Physical and properties-At this time density and refraction index of glass are used most successfully for characterizing glass particles. This is because, the majority of glass fragments are too fragmentary or small to permit comparison Physical and properties-At this time density and refraction index of glass are used most successfully for characterizing glass particles. This is because, the majority of glass fragments are too fragmentary or small to permit comparison Density-2.47-2.54 Density-2.47-2.54 Flotation- method for identifying the density of glass. Mixture of bromoform and bromobenzene may be used to “float a reference/standard piece of glass. (both liquid glass would have the same density. Then glass fragments found at a crime scene are added to the liquid for comparison. If they too float, then the density has been found. Flotation- method for identifying the density of glass. Mixture of bromoform and bromobenzene may be used to “float a reference/standard piece of glass. (both liquid glass would have the same density. Then glass fragments found at a crime scene are added to the liquid for comparison. If they too float, then the density has been found.

38. Flotation Test Based on density Based on density Glass is not perfectly homogeneous Glass is not perfectly homogeneous test allows for small internal density variations test allows for small internal density variations The control glass chip (known density) The control glass chip (known density) immersed in mixture of immersed in mixture of bromoform & bromobenzene bromoform & bromobenzene composition of mixture altered composition of mixture altered until the chip remains suspended until the chip remains suspended

39. Flotation Test The crime object (glass of unknown density) immersed in liquid mixture The crime object (glass of unknown density) immersed in liquid mixture remains suspended remains suspended liquid, control & unknown have same density liquid, control & unknown have same density sinks sinks unknown is more dense than control unknown is more dense than control different origins different origins Accurate density measurements can be obtained with a Density Meter Accurate density measurements can be obtained with a Density Meter

40. Refractive index of various glass Frequency or occurrence of refractive index for samples submitted to FBI GRIMM 1and GRIMM2 are automated instruments used to determine the refractive index of glass particles using the immersion method. Stored in a data bank.

41. Double Refraction Crystalline solids have definite geometric forms! Crystalline solids have definite geometric forms! Crystals refract a beam of light into two different light-ray components Crystals refract a beam of light into two different light-ray components extraordinary ray extraordinary ray refracted (bent) refracted (bent) ordinary ray ordinary ray path unchanged path unchanged Causes a double image to be seen Causes a double image to be seen No double refraction with isometric crystals No double refraction with isometric crystals

42. Birefringence The difference between the two indices of refraction The difference between the two indices of refraction for calcite: 1.486 & 1.658 for calcite: 1.486 & 1.658 birefringence for calcite is 0.172 birefringence for calcite is 0.172 Use in identifying crystals Use in identifying crystals

43. Forensic Characteristics of Soil Soil analysis is concerned with: nature of composition of the soil- rocks, minerals, vegetation, and animal matter nature of composition of the soil- rocks, minerals, vegetation, and animal matter manufactured objects- glass, paint chips, asphault, brick fragments, and cinders whose fragments make the soil unique to a particular location. manufactured objects- glass, paint chips, asphault, brick fragments, and cinders whose fragments make the soil unique to a particular location. forensic soil analysis is comparative in nature- the value of soil as evidence rests with its transferability between the crime scene and the criminal. Ex. - Mud on shoe or clothes links criminal to crime scene. forensic soil analysis is comparative in nature- the value of soil as evidence rests with its transferability between the crime scene and the criminal. Ex. - Mud on shoe or clothes links criminal to crime scene.

44. Forensic Characteristics of Soil Geologists may help direct police to general vicinity where the crime was committed by analyzing soil found on a person thought to have committed a crime. Geologists may help direct police to general vicinity where the crime was committed by analyzing soil found on a person thought to have committed a crime. Soil is classified by color after drying Soil is classified by color after drying (there are nearly 1000 diff. soil colors), and microscopic determination of types of minerals and rocks, animal and plant material, and artificial material. Chemical tests of soil pH, amounts of nitrogen, phosphorous amounts of nitrogen, phosphorous and potassium as well as trace element and potassium as well as trace element amounts are also performed. Tests are amounts are also performed. Tests are performed by forensic geologists with performed by forensic geologists with the goal of cross linking criminal to crime scene. the goal of cross linking criminal to crime scene.

45. Density Gradient Tubes Density-gradient Tubes- a glass tube filled from the bottom to the top with liquids of successively lighter densities; used to determine the density distribution of soil. Density-gradient Tubes- a glass tube filled from the bottom to the top with liquids of successively lighter densities; used to determine the density distribution of soil. Ultimately, the forensic value of soil depends on its variation at the crime scene. Ultimately, the forensic value of soil depends on its variation at the crime scene.

46. Density-gradient tube: a glass tube filled from bottom to top with liquids of successively lighter densities; used to determine the density of soil Density-gradient tube: a glass tube filled from bottom to top with liquids of successively lighter densities; used to determine the density of soil

47. Collection and Preservation of Soil Evidence Standard/reference soils are collected within a 100 yard radius of the crime scene, as well as at the site of the crime for comparison to the questioned soil. Standard/reference soils are collected within a 100 yard radius of the crime scene, as well as at the site of the crime for comparison to the questioned soil. In most cases, only the top layer of soil is removed. In most cases, only the top layer of soil is removed. Only 1-2 tablespoons is collected. Only 1-2 tablespoons is collected. Specimens are packed in individual container like plastic vials. Vials are marked and labeled with collector and site collected. Specimens are packed in individual container like plastic vials. Vials are marked and labeled with collector and site collected. Soil found on a shoe or garment- entire object must individually wrapped in paper bags with no attempt to remove the soil. Soil found on a shoe or garment- entire object must individually wrapped in paper bags with no attempt to remove the soil. Lumps of soil (such as on a car under the fender) should be collected and preserved intact in order to preserve the order to which soil adhered to the car. Lumps of soil (such as on a car under the fender) should be collected and preserved intact in order to preserve the order to which soil adhered to the car.

48. Footprints and Tire Tracks Collection and preservation Before impressions are made, photographs need to be taken. Before impressions are made, photographs need to be taken. shots from directly over with scale as well as from various angles. shots from directly over with scale as well as from various angles. Shots taken to show the position of the impression in relation to the overall crime scene. Shots taken to show the position of the impression in relation to the overall crime scene. Impressions on readily recoverable items, such as glass, paper or tile flooring are sent intact to crime lab. Impressions on readily recoverable items, such as glass, paper or tile flooring are sent intact to crime lab.

49. Impressions made on a surface that can’t be sent to the lab need to be lifted, sometimes like lifting a fingerprint. Impressions made on a surface that can’t be sent to the lab need to be lifted, sometimes like lifting a fingerprint. For impressions made in light deposits of dust or dirt-lifting material needs to be large enough to lift whole impression. Place lifting material over print and use a fingerprint roller to eliminate tiny air pockets For impressions made in light deposits of dust or dirt-lifting material needs to be large enough to lift whole impression. Place lifting material over print and use a fingerprint roller to eliminate tiny air pockets

50. Lifting Devices Portable electrostatic lifting devices (ex. Pathfinder) are another method- Mylar sheet of film is placed on top of the dust mark and a roller is used to press the film against the impression. High voltage electrodes of Pathfinder are then used to create a charge difference between the Mylar film and the surface below the dust mark so that the dust is attached to the lifting film. Portable electrostatic lifting devices (ex. Pathfinder) are another method- Mylar sheet of film is placed on top of the dust mark and a roller is used to press the film against the impression. High voltage electrodes of Pathfinder are then used to create a charge difference between the Mylar film and the surface below the dust mark so that the dust is attached to the lifting film.

51. Casting of footprints and tire tracks- Class I dental stone, a form of gypsum is usually used to cast impressions. Casting of footprints and tire tracks- Class I dental stone, a form of gypsum is usually used to cast impressions. Aerosol product- Snow Impression Wax is used for impressions in snow. Three light coats of wax are applied, and then the print is casted. Aerosol product- Snow Impression Wax is used for impressions in snow. Three light coats of wax are applied, and then the print is casted.

52. Impression Identification comparison is only possible when an item suspected of having made the impressions recovered. comparison is only possible when an item suspected of having made the impressions recovered. Agreement with respect to size, shape, or design may permit the conclusion that a print was made a certain brand of shoe or tire. Agreement with respect to size, shape, or design may permit the conclusion that a print was made a certain brand of shoe or tire. SICAR- automated shoeprint indentication system- uses multiple databases to search for known and unknown footwear files for comparison against footwear specimens linking shoeprints at a crime scene to a another crime scene or to a person who has been in custody that has that shoeprint. Type of shoe can be identified as well. SICAR- automated shoeprint indentication system- uses multiple databases to search for known and unknown footwear files for comparison against footwear specimens linking shoeprints at a crime scene to a another crime scene or to a person who has been in custody that has that shoeprint. Type of shoe can be identified as well. Other web sites are used to link tire tracks to tire manufacturers. Other web sites are used to link tire tracks to tire manufacturers. More significant is the existence of individual characteristics arising from wear, cuts, gouges or other damage. More significant is the existence of individual characteristics arising from wear, cuts, gouges or other damage.

53. Important Vocabulary: Important Vocabulary: Physical property: describes the behavior of a substance without having to alter the substance’s composition through a chemical reaction Physical property: describes the behavior of a substance without having to alter the substance’s composition through a chemical reaction Chemical property: describes the behavior of a substance when it reacts or combines with another substance Chemical property: describes the behavior of a substance when it reacts or combines with another substance Fahrenheit scale: the temperature scale using the melting point of ice as 32 0 and the boiling point of water as 212 0, with 180 equal divisions or degrees between them. Fahrenheit scale: the temperature scale using the melting point of ice as 32 0 and the boiling point of water as 212 0, with 180 equal divisions or degrees between them.

54. Celsius scale: the temperature scale using the melting point of ice as 0 0 and the boiling point of water as 100 0, with 100 equal divisions or degrees between Celsius scale: the temperature scale using the melting point of ice as 0 0 and the boiling point of water as 100 0, with 100 equal divisions or degrees between Weight: a property of matter that depends on the mass of a substance and the effects of gravity on that mass Weight: a property of matter that depends on the mass of a substance and the effects of gravity on that mass Mass: a constant property of matter that reflects the amount of material present Mass: a constant property of matter that reflects the amount of material present Density: a physical property of matter that is equivalent to the mass-per-unit volume of a substance Density: a physical property of matter that is equivalent to the mass-per-unit volume of a substance

55. Refraction: the bending of a light wave as it passes from one medium to another Refraction: the bending of a light wave as it passes from one medium to another Refractive index: the ratio of the speed of light in a vacuum to its speed in a given substance Refractive index: the ratio of the speed of light in a vacuum to its speed in a given substance Crystalline solid: a solid in which the constituent atoms have a regular arrangement Crystalline solid: a solid in which the constituent atoms have a regular arrangement Amorphous solid: a solid in which the constituent atoms or molecules are arranged in random or disordered positions. There is no regular order in amorphous solids. Amorphous solid: a solid in which the constituent atoms or molecules are arranged in random or disordered positions. There is no regular order in amorphous solids.

56. Birefringence: a difference in the two indices of refraction exhibited by most crystalline materials Birefringence: a difference in the two indices of refraction exhibited by most crystalline materials Tempered glass: glass to which strength is added by introducing stress through the rapid heating and cooling of the glass surfaces Tempered glass: glass to which strength is added by introducing stress through the rapid heating and cooling of the glass surfaces Laminated glass- regular window glass with a piece of plastic between. Laminated glass- regular window glass with a piece of plastic between.

57. Becke line: a bright halo that is observed near the border of a particle immersed in a liquid of different refractive index Becke line: a bright halo that is observed near the border of a particle immersed in a liquid of different refractive index Radial fracture: a crack in a glass that extends outward like the spoke of a wheel from the point at which the glass was struck Radial fracture: a crack in a glass that extends outward like the spoke of a wheel from 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 Concentric fracture: a crack in a glass that forms a rough circle around the point of impact Mineral: a naturally occurring crystalline solid Mineral: a naturally occurring crystalline solid