ch14

• a __________ employs a process similar to distillation to remove moisture and oxygen from organic solvents?


  solvent still
• the repeated process of heating a solvent to boiling and condensing its vapor is known as?

  reflux
• A persistent blue-purple color indicates that the solvent is free from ?

  moisture and oxygen
• stainless steel columns with silica, powders with high surface areas and small particle sizes, molecular sieves and copper catalysts powders are safer alternatives to?

  solvent purification
• Ordinary combustible materials need a class _ fire extinguisher?

  A
• Class B fire extinguishers, for flammable liquids such as organic solvents, gas, oil, and paint use what?

  carbon dioxide or dry-chemical
• Electrical fires (Class C) use the same extinguishers as?

  class B
• Combustible metals use dry powder extinguishers which are class?

  D
• Class K extinguishers are?

  wet chemical
• The lowest concentration of solvent vapor that can ignite in air is known as?

  lower flammability limit
• when the vapor pressure of a solvent equals its lower flammability limit, what is reached?

  flash point
• T/F: In assessing the overall flammability of a solvent, the flash point is more diagnostic than its boiling point?

  true
• The more heat that is generated by the reaction of a fuel and an oxidizer, the easier it is to exceed the activation energy of reactants, resulting in ignition
• The use of an accelerant will lead to a more complex burn pattern
• The higher the oxygen content of a fuel, the more completely it will burn
• Out of the common plastics, which has the highest autoignition temperature?

  PC
• what term is used when the majority of exposed surfaces in a room are heated to their autoignition temperatures and emit flammable gases?

  flashover
• what kind of prints are not visible to the naked eye?

  latent prints
• cyanoacrylate is the main ingredient of what?

  superglue
• gas chromatography is used to identify separate components in mixtures of liquids and gases; it consists of liquid or gas being injected onto a column and the retention time, based on polarity matching is calculated
• T/F: acetone is miscible with water: true
• strike anywhere matches contain phosphorus but not red phosphorus since it is relatively stable at room temperature
• T/F: The field of forensics is only applicable to criminal investigation?

  false
• Which of the following describes a basic duty of a forensic scientist?

  All of the above
• Items discovered at a crime scene must be?


  Identified with the collectors initials and date of collection
• A victim's body was found at a crime scene with a body temperature of 90F, at an outside temperature of 65F, the time of death is likely?

  longer than 3 hours prior
• In the US, the national database for DNA profiles for convicted offenders is?

  CODIS
• A cigarette butt is found at a crime scene that matches the DNA of a suspect. Which of the following is correct?

  The suspect may be guilty; investigators must determine when the cigarette butt was deposited
• DNA stands for?


  deoxyribonucleic acid
• DNA is not easily obtained from?

  fingerprints
• Which of the following aspects of forensic investigations portrayed on TV is unrealistic?

  DNA profile are analyzed within a few minutes and match a suspect
• Electrophoresis is used to?

  Separate DNA fragments
• Gas chromatography is used to?

  separate mixtures of gases
• Which of the following represent isotopes?

  13C and 12C and 16O and 18O
• Isotopic analysis can be also use for climate change in which respect?

  Determine past air temperatures
• The unit of permil (permile) is?

  C. 1/000
• Scanning electron microscopy is primarily used to?

  Determine the sizes and shapes of particles comprising a sample
• The image obtained from SEM results from?

  secondary electrons ejected from sample atoms through interaction with an electron beam
• In order to visualize fingerprints from a non-porous surface, the object may be placed within a fuming chamber and exposed to vapors of which substance?


  Cyanoacrylate
•  In order to avoid prosecution, criminals have used acid or sharp objects in an attempt to obscure their fingerprints. Which of the following describes the outcome of this devious attempt?

  B. This is most often not effective since the damage would have to penetrate beyond 1-2 mm beneath the skin's surface