CHM1020C Exam 3 FSU Dillon

What is combustion?

Combustion is burning, usually in air, which is all around us

What kind of reaction is combustion?

An Exothermic Reaction

What is an exothermic reaction?

It means that the reaction gives out heat

What does fuel store that can be released as heat?

potential energy

What is complete combustion?

When burned, releases carbon dioxide and water

What is incomplete combustion?

Produces carbon monoxide and water or carbon and water

What are the effects that come from the products of combustion?

Water vapor: harmless

Carbon Dioxide: is a green house gas

Carbon monoxide: toxic

What are the characteristics of carbon monoxide?

Colorless

Odorless

Tasteless

What is the silent killer?

Carbon Monoxide

What are the three main ingredients for fire?

Oxygen

Fuel

Heat

What is combustion reaction?

The type of reaction that produces fire

What does exothermic mean?

Heat releasing

What does redox mean?

oxygen adding

What are the 4 main methods for stopping a combustion reaction?

Smothering

Starvation

Cooling

Breaking the chain reaction

How does the method of cooling work when stopping a combustion reaction?

Cooling of the temperature removes the overall energy

What are the three reasons that make it hard to investigate arson?

1. The arson can plan out the arson well in advanced and bring the tools needed with them

2. Arsonists do not need to be present at the time of the act

3. The fire destroys evidence tying the arsonist to the crime

What are the common signs of arson?

1. Multiple sites of ignition

2. Lines of accelerant residue

3. Majority of burning takes place on the floor as opposed to the ceiling

4. Presence of unburned combustible liquids

What evidence is collected when looking for arson?

Ash and soot

Vapor detectors can identify different vapors

Samples of different burned materials

Ignition devices

What is the most common method in identifying an accelerant?

Gas chromotograph

What is flash point?

Minimum temperature at which a liquid gives off enough vapor to form an ignitable mixture.

Whats more dangerous a lower or higher flash point?

Lower

What are flammable liquids?

Have flash points below 100 degrees Fahrenheit and are more dangerous than combustible liquids since they may be ignited at room temperature.

What is the minimum flash point for combustible liquids?

100 degrees

What is vapor pressure?

The pressure exerted by the vapor of the liquid at any given temperature

What will happen to the vapor pressure as the temperature increases?

The vapor pressure will increase

Liquids with higher vapor pressure have...?

A lower boiling point

Vapor pressure equals atmospheric pressure at what point?

The boiling point

What kind of liquids are easiest to burn?

Liquids with a low boiling point and a high vapor pressure

Sudden buildup of gas pressure constitutes a what?

Explosion

What are the two reasons that explain why TNT is explosive?

1. TNT is composed of carbon, oxygen, and nitrogen. When it explodes it forms several covalent gases

2. TNT is high energy and unstable

What are the 3 major classes of explosives?

Low

Primary High

Secondary High

What are low explosives?

Those that burn only at their surface

What are primary high explosives?

Those that are ultra sensitive to heat, shock, or friction and provide the major ingredients used as a detonator.

What are secondary high explosives?

They require an electric spark or fuse and they are insensitive to heat shock and friction

What do you do when you are collecting evidence at the scene of an explosion?

1. locate the epicenter

2. collect objects near the scene

3. Collect lose soil in the crater

4. Ion mobility spectrometer

What does an ion mobility spectrometer do?

Detects and separates ions in the gas phase

What is chemical kinetics?

The study of reaction rates, how reaction rates change under varying conditions, and by which reaction the mechanism proceeds

What are the 5 properties that affect the rate of reaction?

1. The concentration of the reactants

2. Temperature

3. Physical state of reactants

4. The presence

5. Light

Them more concentration...?

The faster the rate of reaction

How does increasing temperature effect a reaction?

It speeds it up

Why do powders react faster than blocks?

The powder has more surface area than the blocks

A catalyst __________ up a reaction, the ___________ slows it down

speeds

inhibitor

What lowers the activation energy?

Catalyst

How does concentration affect the rate of reaction?

Increasing the concentration will increase the frequency of collisions

What affect does pressure have on the reaction between two gasses?

When you increase the pressure you squeeze the molecules which increases the amount of collisions.

What are rate expressions?

Describes reactions in terms of the change in reactant or product concentrations over the change in time

What are the rules for writing expressions?

1. Reactants are given a negative sign

2. Products are positive

What is The Rate Method?

Time of death is estimated by the presence of an indicator in a deceased in conjunction with the known behavior of such indicators

What is the concurrence method?

Time of death is estimated by evaluating events which happen at or near the time of death, or offer information suggesting a time period for the death event

What is Rigor Mortis?

The stiffening of the body

Warm body, no rigor

death under 3 hours

warm body and stiff

death 3-8 hours

cold body and stiff

death 8-36 hours

cold body and not stiff

death more than 38 hours

What happens to rigor if it is hot or cold?

hot-increase

cold-decrease

How will strenuous activity before death effect rigor?

Increase Rigor

What is Livor Mortis?

Setting of blood in a body due to gravity

When does livor mortis develope?

2-4 hours after death

When is a body blanchable?

8-12 hours after death

What is Petechial Hemorrhages?

Small vessels breakdown through the body

What is blanching?

When you press on skin and a white spot occurs

What is Algor Mortis?

The cooling of the body after death

What is the Glastier Equation?

Used to determine time of death using body temperature

What stage is there filming over the eyes?

Algor

What is Autolysis?

digestive enzymes in the body break down carbs and proteins

What is putrefaction?

Predominant cause of tissue degradation

What are the 4 stages of putrefaction?

1. Putrefaction 4-10 days

2. Back putrefaction 10-20 days

3. Butyric fermentation 20-50 days

4. Dry decay 50-365 days

What is death?

Termination of all biological function that sustain a living organism

What are the signs of death?

No breathing

No heartbeat

No pupillary response to light

No response to pain stimuli

What is ATP responsible for?

Flexing muscles

What is forensic entomology?

Area of investigation that uses bugs to determine time of death

What is cyropreservation?

Freezing the body to stop decomposition

What are the physical properties of metal?

Shininess, malleability, ductility, and conductivity

What is malleable?

Material that can be hammered or rolled into sheets

What is ductile?

Material that can be made into long wire

How are metal atoms arranged?

cubic cell

3 types of packing in transition metals

1. Face- Centered cubic

2. Body-centered cubic

3. Hexagonal close packed

What are grains?

regions of irregular structure that exist in the overall crystalline structure of the metal

What happens to the grains when it is cooled quickly?

Small grains

The smaller the grains...?

Harder the metal

What does cellulose do for wood?

Makes it strong and resistant to breakage

What are polymers?

Long chain of linked molecules

What does Lignin do for wood?

Makes it resistant to compression

What is a ligature?

rope or wire that is used to suffocate a victim

What is muzzle velocity?

The rate at which a projectile leave a gun

What are characteristics of stab wound?

clean cut edges

gape opening

What are the three main wound types?

Slash- side to side

Puncture- straight in

Incision- up and down

What are the twp ways the brain is injured by bunt force trauma?

Damage to cerebral cortex causing brain death

Piece of bone enters the brain

What are things a victim will experience when being suffocated?

convulsions

bleeding from ears, mouth, and noes

What is a garrote?

A handled ligature

What is asphyxia?

Body is deprived of oxygen called hypoxia

What is hypoxia?

Oxidative stress that causes a reaction in the body through several single pathways that eventually lead to cellular apoptosis.

What is cellular apoptosis?

Cell death

What is cerebral Anoxia?

Total cutting off of oxygen to the brain

What are the different classifications of gun shot wounds?

Contact

Intermediate range

distant range

What do contact wounds look like?

soot on the outside of the skin

muzzle imprint

laceration from the

What do intermediate wounds look like?

powder stippling

lack of muzzle imprint of laceration

What do distant range wounds look like?

lack powder stippling

exhibit a hole roughly the size of the caliber of the projectile

What is an abrasion?

Any cut, scrape, friction burn, or grazing of the victim

What is a laceration?

Tearing of tissue underneath the skin