Forensic 3

Organic

Carbon Based

Inorganic

Non carbon based

Compounds

Substances composed of two or more elements combined chemically, more than one atom

Molecule

Is a combination of two or more atoms (can be the same or different), smallest unit of a compound that retains its physical and chemical properties. All compounds are molecules, molecules encompass more !

Electron

negatively charged, basically no mass

Proton

Positively charged, mass necessary

Neutron

Neutral, no charge considered equal in mass to a proton (slightly greater)

Ion

Atoms gaining or losing an electron indicating a positive or negative charge

Cation

Positively charged, when atom loses electrons

Anion

Negatively charged, when atom gains electrons

Isotope

Same element with the same number of protons yet the number of neutrons is different (# of protons indicates what the element is)

Atomic #

#

of protons

Atomic mass

#
of protons + # of neutrons

Periodic Table

Metals left, non metals right

Group 1

Alkali metals

Group 2

Alkali earth metals

Group 3-12

Transition metals

Group 17

Halogens

Group 18( last row )

noble gases

Metals !

Conduct heat/electricity , lustrous (shiny, ductile (stretch/deform without breaking), malleable, most are solid at room temperature (mercury exception)

Non metals!

Don’t conduct, aren’t ,lustrous, nor ductile, or malleable, gases at room temperature
Hydrogen nitrogen oxygen etc

Semi-metals

Lie between metals and non metals, boron, silicone, arsenic, germanium

Maybe know Griess test

Modified Greiss Test: A series of
chemical reactions result in the
conversion of any nitrite compounds
that may be present on an item, such
as victim clothing, into a bright orange
dye in a chromophoric reaction

Oxidation

Chemical reaction between a substance and oxygen, fire is a result of an oxidation reaction! as fast one, too fast u get explosion, too slow you rust

Exothermic reactions

Produce heat

Endothermic reactions

Take in heat, absorb

Activation energy

The amount of energy required for reactants to overcome the energy barrier for their reaction, min amount of energy required

Spontaneous reactions

Happens naturally on its own, releases energy

Non spontaneous reactions

Does not happen naturally, requires continues external energy , absorbs energy

Ignition Temperature

The temperature at which the ignition needs to be in order to light up the fire, the activation energy per se

Complete combustion

Produces C02 and H20

Incomplete Combustion

Carbon monoxide is produced

Flash Point

Minimum temperature at which a liquid fuel will produce enough vapor to be ignited by a source (needs an ignition source)

Flammable liquids

Flash points below 100 degrees F (gasoline, acetone, ethyl alch)

Combustible liquids

Flash points of 100 degrees F or more (kerosene, fuel oil)

Accelerant

Material used to start or sustain a fire

Point of Origin

Place where fire starts, and fire burnt longer there so it is the place of greatest amount of damage, and fire fans out from that point, so damage is less on the outer parts

Flashover

temperature at which a fire begins unrestricted growth and causes complete destruction

Pyrolysis

Breaking of solids in fire, toxic gas could be released

Fire Tetrahedron

Heat + Fuel+ Oxygen and Chain Reaction. Heat is needed to begin the fire, must be ignited with a source providing activation energy aswell as maybe accelerant is above flash point. Then oxygen fans the flames, it reacts with the fuel to keep the fire going, apart of the oxidation reaction, no oxygen and the fire will go out. Fuel is what the fire uses to keep burning, it’s what the fire envelopes, the material that burns. A chain reaction occurs and the fire keeps burning as long as it has these three things holding it up. Self sustaining chemical reactions that produces heat/reactive particles and keeps the combustion process going

Explosion

release of mechanical or chemical energy in a violent manner that generates heat and releases large quantities of gas

Low Explosives

Explosions occur less than the speed of sound, hear sound first then you see explosion, deflagration

High Explosives

Explosions occur faster than the speed of sound, may feel the jerk first then hear the sound (detention)

Dynamite (Alfred nobel)

Made large scale blasting possible

Now what is used?

Ammonium nitrite

Chemical tests used to establish high explosive compositions

Thin layer chromatography
Gas chromatography
Infrared tests
Ion chromatography

Taggants

microscopic pieces of plastic in explosive to indicate source of manufacture