Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Forensic Chemistry > Combustion > Flashcards

Combustion Flashcards

Forensic Chemistry

1
Q

What is a combustion reaction?

A
  • Fuel reacting with oxygen and light energy.
  • Water and carbon dioxide are produced.
  • Three types of fuels and they are gas, solid and liquid.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Which type of explosives do not contain oxygen?

A
  • Azide groups, as they naturally do not contain oxygen.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is required and produced in a combustion reaction?

A
  • Required= oxygen , fuel, heat energy.
  • Produced= carbon dioxide, water vapour, light energy.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Is combustion an endothermic or exothermic reaction?

A
  • Exothermic.
  • Heat being released to the surroundings.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How is a combustion reaction initiated?

A
  • When the fuel and oxygen are in the correct ratio.
  • There is enough heat to break the bonds of the reactants and for the products to form.
  • It is a chain reaction, as the energy that has been released will further break bonds in the reactants.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When will a combustion reaction finish?

A
  • When all of the fuel is consumed first.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

When will an explosive reaction finish?

A
  • When all of the oxygen is consumed first.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is detonation combustion?

A
  • The speed of combustion reaction is faster than the speed of sound.
  • A sonic reaction.
  • Shockwaves have the ability to destroy anything in their path.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is deflagration combustion?

A
  • The speed of the combustion reaction is slower than the speed of sound.
  • A subsonic reaction.
  • A wave on flame front is produced.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What will happen if there is not enough oxygen in a combustion reaction?

A
  • Combustion will not take place.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a lean mixture?

A
  • When there is too much oxygen compared to fuel in a reaction.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a rich mixture?

A
  • when there is too much fuel compared to oxygen in a combustion reaction.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a pyrolyzable solid and give an example.

A
  • An example is wood and will decompose by pyrolysis when there is oxygen and high temperatures.
  • Pyrolyzable gases will be produced and they will react with oxygen to produce heat and fire.
  • When all the wood has been consumed, a carbon based residue will remain and it undergoes glowing combustion.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a non-pyrolyzable solid and give an example.

A
  • An example is charcoal or cigarettes.
  • Glowing combustion occurs, which is oxidation at every surface.
  • Oxidation occurs at the outer surface and then it works on the next surface until there is nothing left.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the thermodynamics equation and what does each part of the equation stand for?

A

^G = ^H- T . ^S

^G= Gibbs free energy
^H= Change in enthalpy
^S= Change in entropy
T= temperature in k

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Will Delta G have a positive or negative value in a combustion reaction?

A
  • Delta G will have a high negative energy of free energy.
  • Delta S will be positive as the gaseous products are cladding with one another.
  • Delta H will have a negative value.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does detonate mean?

A
  • Explode or cause to explode.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a primer in a gun barrel?

A
  • it is an explosive.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe a bullet ejection from a gun barrel.

A
  • The firing pin in a gun strikes the primer, which is an explosive.
  • The primer detonates and it produces a flame.
  • The flame ignites the propellent which produces gases.
  • The gases travel down the gun.
  • Mechanical energy is converted into heat energy.
  • Heat energy is then converted into chemical energy, which is then converted into kinetic.
20
Q

Put in order all the types of energies in a bullet ejection in a gun barrel.

A
  1. Mechanical
  2. Heat
  3. Chemical
  4. Kinetic
21
Q

What can a candle flame be known as?

A

A Laminar flame

22
Q

What is a candle made out of?

A
  • Hydrocarbons
23
Q

How big are the carbon particles in a candle?

A
  • 20 nanometres.
24
Q

What part of a candle has the lowest temperature and why?

A
  • The wick as it contains large alkanes.
25
Q

What is the blue flame known as in a candle and why?

A
  • Hydrocarbon cracking region.
  • Hydrocarbons are being broken down.
  • The aborption and emission of light.
26
Q

What does UFL and UEL mean?

A

UFL= upper flammability limit.
UEL= upper explosive limit.

27
Q

What does LFL and LEL mean?

A

LFL= low flammability limit.
LEL= low explosive limit

28
Q

What is a conventional fire and what pattern shape is produced?

A
  • Gases move upwards and outwards from the origin of the fire.
  • A V shape pattern is produced.
29
Q

What two types of conventional fires are there?

A
  • Flashover
    -Backdraft
30
Q

Describe a flashover fire.

A
  • The point during a fire where all the flammable vapours ignite.
  • A layer of hot smoke is produced which is across the ceiling, heat is radiated downwards.
  • Anything which is flammable will decompose and produce vapours.
  • Temperature will exceed 600 and flashover will occur.
  • Flashover will destroy everything.
31
Q

Describe a backdraft fire.

A
  • When the fire is contained in a room and it is starved of oxygen.
  • The temperature is high enough for any flammables to combust and to produce vapours.
  • If a door or window is opened and oxygen enters the room, it will combust into a flaming fire.
32
Q

What is a shockwave?

A
  • They are formed by pressurised air.
  • They can be devastating.
33
Q

What is the relationship between the density of an explosive and its speed.

A
  • The higher the density of an explosive the higher the speed of detonation.
  • The explosive that has the highest density and speed is HMX and the lowest explosive is TNT.
34
Q

What are explosives made up of?

A
  • They have a carbon hydrogen back bone.
  • Carbon and nitrogen is contained in it.
  • For azide groups, oxygen needs to be added so they can undergo combustion.
  • When the explosive detonates, water vapour, carbon dioxide and nitrogen gas.
35
Q

What are molecular explosives and give an example.

A
  • They are difficult to handle and unstable.
  • Explosive in their purest form.
  • An example is mercury fulminate.
36
Q

Describe low explosives and give an example.

A
  • Deflagation explosive.
  • Will detonate in a confined space.
  • A shockwave will be produced at 100m/s and will produce a propelling or throwing action.
  • An example of an explosive is black powder and flares.
37
Q

Describe high explosives.

A
  • Can be split into primary and secondary explosives.
  • Decomposed by high pressure.
  • Detonation explosive, shockwave moving faster than the speed of sound.
38
Q

What is a primary explosives and provide an example.

A
  • They are ultra sensitive.
  • Will produce a powerful shockwave that can detonate a secondary explosive.
  • An example is lead azide.
39
Q

What is a secondary explosive and provide three examples.

A
  • They are classed as main explosives.
  • Will burn as they are sensitive to shock and friction.
  • shock wave will only detonate from a primary explosive.
    Three examples are:
    1. Dynamite
    2. ANFO
    3. Semtex
40
Q

Describe propellents.

A
  • They ignite.
    -Used to accelerate a projectile.
    -Smokeless powders are used.
41
Q

Name the three smokeless powders.

A
  1. Single base- nitrocellulose.
  2. Double base- nitrocellulose and nitroglycerine.
  3. Triple base- nitrocellulose, nitroglycerine, nitroguanidine.
42
Q

How many bullet shockwaves are there and what are they known as?

A

1st shockwave= known as the mach cone and comes from the bullet nose.
2nd shockwave= known as the cannelure and comes from the middle of the bullet.
3rd shockwave= known as the wake and comes from the base of the bullet.

43
Q

What does GSR stand for?

A
  • Gun shot residue.
44
Q

What is GSR made up of?

A
  • Antimony, lead and barium.
  • For a positive result all three need to be present.
45
Q

How can GSR be analysed?

A

-Analysed by using Scanning electron microscopy-energy dispersive X ray (SEM-EDX).
- Can determine the elemental composition of the particles.
- Can produce images of the particles.

46
Q

What factors can affect the rate of a bullet?

A
  • Burnt rate
  • Rate of production gas
  • Burn pattern
47
Q
A

Forensic Chemistry (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions