1. LABORATORY ANALYSIS Forensic Science

2. Elements and Compounds A. Matter - anything that has mass & takes up space B. Element - cannot be broken down into simpler substances by chemical means C. Periodic table - chart of elements arranged in a systematic fashion D. Atom - smallest particle of an element that can exist and still retain its identity as that element

3. Mixtures & Compounds Mixture – Two or more substances that are mixed together, but not chemically combined. Examples of mixtures... Air – mixture of gases Bowl of cereal – mixture of cereal and milk Soda pop – mixture of soda syrup, water, and CO 2 gas Fog –water suspended in air Kool-Aid – mixture of water, sugar, and flavor crystals Examples of compounds... Salt –Sodium and chlorine combined chemically Water –Hydrogen and oxygen combined chemically Carbon Dioxide – Carbon and oxygen combined chemically Compounds – Two or more elements that are chemically combined.

4. Solutions Solutions are mixtures in which one substance is dissolved in another. Solutions have two parts: solute and solvent The solute is the substance that is dissolved. The solvent is the substance that does the dissolving Identify the solute and solvent in each solution... SolutionSoluteSolvent Lemonade Soda pop Ocean water Solubility - A measure of how much of a given substance will dissolve in a liquid. A substance that does not dissolve in water is called insoluble. A substance that does dissolve in water is called soluble.

5. The periodic table is a listing of all elements by increasing atomic number.

6. The vertical columns are called groups. There are 18 groups The horizontal rows are called periods. There are 7 periods.

7. The periodic table can be separated into metals, nonmetals, and metalloids.

8. Metals are shiny, malleable, ductile, and good conductors of heat and electricity.

9. Nonmetals are not shiny, malleable, ductile, or good conductors of heat and electricity.

10. Physical states Substances change from one state to another Phase - a uniform piece of matter, different phases are separated by definite visible boundaries There are four phases of matter: solid, liquid, gas, and plasma.

11. Phase Changes – Physical Changes Evaporation = Condensation = Melting = Freezing = Sublimation = Liquid -> Gas Gas -> Liquid Solid -> Liquid Liquid -> Solid Solid -> Gas

12. Solids particles vibrate but can’t move around fixed shape fixed volume incompressible

13. Liquids particles can move around but are still close together variable shape fixed volume Virtually incompressible

14. Gases particles can separate and move throughout container variable shape variable volume Easily compressed Vapor - gaseous state of a substance that is a liquid or solid at room temperature

15. Plasma particles collide with enough energy to break into charged particles (+/-) gas-like, variable shape & volume stars, fluorescent light bulbs, TV tubes

16. Four States of Matter

17. Selecting an Analytical Technique Need to know whether substance is organic or inorganic A. Organic - substance composed of carbon and hydrogen B. Inorganic - CO 2 and all substances that lack carbon Need to consider the need for qualitative and quantitative determination

18. Organic Analysis Spectrophotometry Chromatography Gas Chromatography (GC) High – Performance Liquid Chromatography (HPLC) Thin – Layer Chromatography (TLC) Electrophoresis

19. Spectrophotometry An analytical method for identifying a substance by its selective absorption of different wavelengths of light Most applicable to organic analysis Optimum utilization requires that a material be in relatively pure state

21. Chromatography Organic mixtures are separated into their components by their attraction to a stationary phase while being propelled by a moving phase. Useful technique for purifying substances 1 st observed in 1803 by William Henry (Henry’s Law) One phase is always made to move continuously in one direction over a stationary or fixed phase It’s like a race between chemical compounds. At the beginning, all substances are mixed together. As the race progresses, those that have preference for the moving phase will move faster and pull ahead of others. At the end, all the substances are separated.

24. Gas Chromatography (GC) separates mixtures on the basis of their distribution between a stationary liquid phase and a moving gas phase used widely because of its ability to resolve a highly complex mixture into its components within a time period usually measured in minutes is very sensitive sample must be vaporized and passed through heated tube

27. High-Performance Liquid Chromatography (HPLC) Different types of stationary phases (usually non- aqueous) with a liquid moving phase can perform process at room temperature used for organic explosives and drugs that are heat sensitive

28. Thin-Layer Chromatography (TLC) incorporates solid stationary phase & liquid moving phase because most compounds are colorless, uses UV light to reveal those that fluoresce cannot by itself provide absolute identification; has to be used in conjunction with other procedures to prove absolute identity powerful tool for solving analytical problems rapid and sensitive minimal cost and space requirements

30. Electrophoresis related to TLC in that it separates materials according to their migration rates on solid phase uses electrical current instead of moving liquid phase characterization of proteins, enzymes, and DNA

32. Gas Chromatography Used to determine the chemical composition of unknown substances, such as the different compounds in gasoline shown by each separate peak in the graph below. Paper Chromatography Can be used to separate the components of inks, dyes, plant compounds (chlorophyll), make-up, and many other substances Liquid Chromatography Used to identify unknown plant pigments & other compounds. Thin-Layer Chromatography Uses thin plastic or glass trays to identify the composition of pigments, chemicals, and other unknown substances. Examples of Chromatography

33. Paper Chromatography Lab Obtain the supplies you’ll need. 1 large beaker (or plastic cup) 1 small beaker (or plastic cup) filled with water 4 pieces of filter paper 4 black markers for testing 4 small pieces of masking tape Pencil (to attach to the top of the filter paper) Permanent marker Timer Write the pen number on a piece of masking tape with a permanent marker and place it at the top of the strip. Choose one of the testing markers and draw a thick line near the bottom of the filter paper - about ¼ inch from the bottom. Pour a small amount of water into the large cup and then hang the paper strip in the cup. Make sure the ink line does not touch the water – only the bottom of the filter paper. Allow the water to move up the paper for 5 minutes and then remove the strip from the water. Hang it on the side of the table to dry. Follow these directions to test the other pens. Pencil Filter Paper Ink Mark Tape – Label with marker

34. Questions: What colors did your group observe in each of the black ink samples? Do the colors occur in the same order on all the samples? Explain. Did some ink samples not work? Why? Complete the chart on your worksheet and then answer the questions.

35. Work with your group to identify the pens used for each of the “Mystery Marks”. 1 st – Test each of the Mystery Mark strips using the procedure from yesterday. 2 nd – Compare your strips to the strips hanging in the classroom. 3 rd – Write the number of the pen that you think matches each of the mystery marks in the space on your worksheet. 4 th – Have your answers checked by the teacher. Keep trying until you are able to identify all 6 pens! Pen A matches # _____Pen D matches # _____ Pen B matches # _____Pen E matches # _____ Pen C matches # _____Pen F matches # _____ Chromatography Challenge

36. Inorganic Analysis Carbon does not appear among earth’s most abundant elements. Inorganics are also encountered as physical evidence Metals in tools, coins, weapons, scrapings Pigments in paints and dyes Explosive formulations Poisons For ID & comparison of physical evidence

38. The Emission Spectrum of Elements Elements selectively absorb and emit light When the light passes through a prism, it is separated into its component colors or frequencies (emission spectrum). Types of emission spectrums Continuous spectrum shows a continuous band of colors all blending into one another Ex – sunlight or light from incandescent bulb passes through a prism

39. Types of Emission Spectrum cont. Line spectrum 1. shows a series of lines separated by black areas 2. Each line represents a definite wavelength or frequency 3. Ex – light from a sodium lamp or mercury arc lamp

40. Emission Spectrograph instrument used to obtain and record the line spectra of elements Requires: 1) a means for vaporizing and exciting the atoms of elements so that they emit light 2) a means for separating light into its component frequencies 3) a means for recording the resultant spectrum Uses in Forensics: Rapid comparison of the elemental composition of two or more specimens

42. Inductively Coupled Plasma (ICP) Emission Spectrometry Identifies and measures elements through light emitted by excited atoms Uses hot plasma torch instead of electrical arc to excite atoms Has been applied in the area of identification and characterization of mutilated bullets and glass fragments

44. Atomic Absorption Spectrophotometer When an atom is vaporized, it will absorb many of the same frequencies of light that it emits in an excited state. In this technique, the specimen is heated to a temperature that is hot enough to vaporize its atoms while leaving a substantial number of atoms in an unexcited state. Provides a determination of an element’s concentration Useful in detecting trace amounts of elements Drawbacks: only one element at a time each time the proper lamp has to be selected to match the particular element under investigation

46. Origin of Emission & Absorption Spectra Subatomic particles Proton – positive electrical charge; in nucleus Neutron – neutral particle; in nucleus Electron – negative charge; outside the nucleus # of protons = # of electrons in a neutral atom

47. Electrons and Energy Electrons move around the nucleus and are confined to specific electron orbitals or energy levels. Atoms are most stable when all of the electrons are in the lowest possible energy orbitals. When the atom absorbs energy (heat or light), its electrons are pushed into higher energy orbitals. (excited state) Only a definite amount of energy can be absorbed when moving an electron from one level to another.

48. Elements are selective in the frequency of light they absorb. Energy levels determine the selectivity. If atoms are exposed to intense heat, energy is generated to push electrons into higher unoccupied energy levels. Normally, an electron does not remain in this excited state for long, but falls back to its original energy level. As it falls, it releases energy in the form of light. Because each element has its own characteristic set of energy levels, each will emit a unique set of frequency values providing a “picture” of the energy levels that surround the nucleus of each element.

49. Neutron Activation Analysis Atoms of the same element have the same number of protons. They do not always have the same # of neutrons. Atomic mass - the # of protons + # of neutrons Isotopes - atoms with the same # of protons but different # of neutrons Most elements have two or more isotopes, and most are stable. Isotopes that are unstable and decompose are considered radioactive.

51. Radioactivity Atoms having the same number of protons but differing solely in the number of neutrons are called isotopes. Most elements have two or more isotopes and most are stable. Isotopes that are unstable and decompose are considered to be radioactive. Radioactivity is the emission of radiation that accompanies the spontaneous disintegration of unstable nuclei.

52. Radioactivity Types Alpha particles (  )– composed of a helium nucleus; positive charge Beta particles (  ) – electrons; negative charge Gamma rays (  ) – high energy form of electromagnetic radiation emitted by a radioactive element

53. Neutron Activation Analysis The technique of bombarding specimens with neutrons and measuring the resulting gamma-ray radioactivity Advantage – provides a non-destructive method for identifying and quantitating trace elements It has been employed for characterizing the trace elements present in metals, drugs, paint, soil, gunpowder residues, and hair.

54. X-Ray Diffraction Technique for identifying crystalline materials As x-rays penetrate the crystal, a portion of the beam is reflected by each of the atomic planes. They interact with one another to form a series of light and dark bands known as a diffraction pattern Every compound is known to produce its own unique diffraction pattern, thus giving analysts a means for “fingerprinting” compounds Drawback – not very sensitive and often fails to detect the presence of substances comprising less than 5% of a mixture

56. The Microscope An optical instrument that uses a lens or combination of lenses to magnify and resolve the fine details of an object

57. Images Virtual image Can only be seen by looking through a lens and cannot be viewed directly Real image Can be viewed directly

58. Types of Microscopes Magnifying glass Magnification of 5-10 times Single lens Compound Light Microscope Comparison Microscope Stereoscopic Microscope Polarizing Microscope Microspectrophotometer Scanning Electron Microscope (SEM)

59. Compound Light Microscope Magnification up to 1500 times Multiple lenses Objective lens lower lens of a microscope that is positioned directly over the specimen Eyepiece lens lens of a microscope into which the viewer looks, same as ocular lens

61. Mechanical system base – support on which instrument rests arm – C-shaped/handle/support stage – horizontal plate upon which specimens are placed for study body tube – hollow tube on which objective and eyepiece are mounted at opposite ends coarse adjustment – focuses lenses fine focus – focuses but on smaller magnitude

62. Optical system Illuminator transmitted illumination – light that passes up from condenser and through specimen vertical or reflected illumination – illumination of a specimen from above Condenser – collects light rays from illuminator and concentrates them onto specimen Objective lens – lens closest to specimen most microscopes are parfocal – when an image is focused with one objective in position, the other objective can be rotated into place and then the field will remain in focus Eyepiece or ocular lens monocular – one eyepiece binocular – two eyepieces

64. Optical system (cont.) Magnifying power : power of objective lens x power of eyepiece lens Numerical aperture The ability of an objective lens to resolve details into separate images instead of one blurred image is directly proportional to the numerical aperture. Ex. A lens with a NA of 1.30 can separate details that are twice as close as compared to lens with NA of 0.65. Field of view the area of the specimen that can be seen after it is magnified as magnifying power increases, field of view decreases Depth of focus the thickness of a specimen entirely in focus under a microscope decreases as magnifying power increases

65. Comparison Microscope Two compound microscopes combined into one unit Uses a bridge incorporating a series of mirrors and lenses to join them Very useful in forensic science when side-by-side comparisons are necessary Vertical or reflected illumination Used when comparing bullets, cartridges, other opaque objects Transmitted illumination Compare hairs or fibers

68. Stereoscopic Microscope Power of 10x to 125x Can present a 3-D image of object Formation of right side up image Very frequently used in crime lab Wide field of view and great depth of focus Used often for examination of paint, soil, gunpowder residues, marijuana, etc.

69. Polarizing Microscope When a beam of light passes through certain types of substances, it emerges vibrating in only one plane. Plane-polarized light: Light confined to a single plane of vibration

70. Polarizing Microscope (cont.) Polarizer: Device that permits passage of light waves vibrating in only one plane Second polarizing crystal – analyzer Can modify stereo or compound microscopes so they can detect polarized light Application – study materials that polarize light ex. Birefringent substances

71. Microspectrophotometer An instrument that links microscope to a spectrophotometer Spectrophotometer - an instrument used to measure and record the absorption spectrum of a chemical substance Allows better comparison of substances

72. Scanning Electron Microscope (SEM) Image is produced by aiming a beam of electrons onto the specimen and studying electron emissions on a closed TV circuit or computer High magnification High resolution

73. Scanning Electron Microscope (SEM) (cont.) High depth of focus Used as tool for determining whether or not a suspect has recently fired a gun X-ray analyzer