Chapter 14

Question 1

Oxidation

Answer 1

the combination of oxygen with other substances to produce new substances; rust is also oxidation, but does not produce fire because of energy levels

Question 2

Energy

Answer 2

the ability or potential of a system or material to do work

Question 3

Energy Forms

Answer 3

heat energy, electrical energy, mechanical energy, nuclear energy, light energy, chemical energy

Question 4

Heat transfer: conduction

Answer 4

electrons of atoms within a heated object collide with one another (metals are best conductors)
Insulators: poor conductors of heat (wood)

Question 5

Heat transfer: radiation

Answer 5

heat energy from a heated surface transfers to a cooler surface by radiation, exposes surfaces to radiant heat, which burst into flame at ignition temperature

Question 6

Heat transfer: convection

Answer 6

transfer of heat energy by movement of molecules within a liquid or gas; heated molecules spread apart and move upwards, cooler molecules migrate to the bottom

Question 7

Combustion

Answer 7

the rapid combination of oxygen with another substance, accompanied by production of noticeable heat and light

Question 8

Heat of Combustion

Answer 8

the heat liberated during combustion, excess energy from exothermic reaction

Question 9

Exothermic reaction

Answer 9

more energy is liberated than is required to break the chemical bonds

Question 10

Endothermic reaction

Answer 10

reaction that requires more energy than it liberates

Question 11

Requirement for initiating combustion

Answer 11

Energy (heat), temperature raised to exceed energy barrier

Question 12

Ignition temperature

Answer 12

minimum temperature at which fuel spontaneously ignites

Question 13

Requirement for sustaining combustion

Answer 13

enough heat is liberated to keep reaction going, burns until either oxygen or fuel is exhausted

Question 14

Headspace technique

Answer 14

way to recover accelerant residues: heat airtight container & remove vapor (or headspace) is removed with a syringe and put into gas chromatograph; disadvantage is size of syrings

Question 15

Vapor Concentration

Answer 15

Charcoal-coated strip is placed within container holding debris collected from the scene, then heated, it absorbs accelerant vapor, washed with acetone and inserted into chromatograph; advantage is sensitivity

Question 16

GC/MS

Answer 16

usually GC is enough but if accelerants are combined with other things, MC may be needed

Question 17

Searching the scene

Answer 17

locating fire’s origin is main focus, can show signs of arson by separate, unconnected fires and burns on floors as opposed to ceilings

Question 18

Searching for accelerants

Answer 18

liquid seeps into porous surfaces: should be collected; can be found with portable vapor detector

Question 19

Packaging and preservation

Answer 19

2-3 quarts of ash and soot debris must be collected at point of origin, all porous materials must be collected, all materials must be packaged in airtight containers (new, clean paint cans filled ½-2/3 full), plastic is not suitable for packaging evidence