3524090
| Pregunta | Respuesta |
| Matter | Anything that occupies space and has mass |
| Physical change | occurs when a substance remains chemically unchanged but changes in size,shape, or appearance |
| Chemical change | occurs when a substance changes from one type of mass into another |
| Energy | the capacity to perform work |
| Potential energy | represents the amount of kinetic energy that an object can release at some point in the future |
| Kinetic Energy | the energy possessed by a moving object |
| Law of Conservation of Mass | states that mass and energy can be converted from one to another, but there is never any net loss of total mass/energy |
| Exothermic reactions | chemical reactions that release thermal energy (ex fire) |
| Endothermic | chemical reactions that absorb thermal energy (ex water from a liquid to a gas) |
| Pyrolysis | the chemical decomposition of a solid material by heating |
| Vaporization | physical process that changes a liquid into a gaseous state - rate of vaporization depends on substance involved, heat, pressure, and exposed surface area |
| Piloted ignition | the moment when a mixture of fuel and oxygen encounters an external heat source with sufficient heat to start the combustion reaction |
| Autoignition | the initiation of combustion by heat but without a spark or flame to ignite the fuel gases or vapor |
| Autoignition temperature | lowest temp at which a combustible material will ignite without an external source of ignition |
| 2 modes of combustion | Non Flaming - use fire triangle - incipient and smoldering stages Flaming - aka fire - use fire tetrahedron |
| Products of combustion | Thermal energy, Smoke, Flame |
| Products commonly found in smoke | CO, HCN, CO2, Irritants |
| Fire triangle | fuel,O2, heat - elements necessary for combustion |
| Fire tetrahedron | fuel,O2,heat,chemical reaction - 4 conditions required to HAVE a fire |
| 3 common sources of thermal energy | Chemical (most common), Electrical, Mechanical |
| What is self heating | Chemical energy - form of oxidation, is a chemical reaction that increases the temp of a material without addition of external heat |
| Types of electrical heating (4 points) | Resistance heating Overcurrent/Overload Arcing Sparking |
| Types of mechanical energy | Adiabatic compression Friction Friction sparks |
| Law of heat flow | states the energy will flow from a hot surface to cold |
| Types of heat transfer | convection,conduction,raditation |
| Conduction | the transfer of heat through or between solids that are in direct contact |
| Convection | the transfer of thermal energy by the circulation or movement of a fluid (liquid or gas) |
| Radiation | the transmission of energy as an electromagnetic wave without an intervening medium factors: nature of exposed surfaces,distance,temp difference |
| Heat of combustion | total amount of thermal energy that could be generated by the combustion reaction if a fuel source were completely burned - measured in megajoules |
| Heat release rate (HRR) | total mount of heat released per unit time - measured in kilowatts - dependent on type, quantity, and orientation of fuel |
| Specific gravity | ratio of the mass of a given volume of a liquid compared with the mass of an equal volume of water at the same temperature water = 1 less than=floats / greater than=sinks |
| Vapor pressure | pressure that vapors escaping from a liquid exert |
| Flashpoint | minimum temp at which a liquid gives off sufficient vapors to ignite but not sustain combustion |
| Fire point | temp at which sufficient vapors are being generated to sustain the combustion reaction |
| Solubility | describes the extent to which a substance will mix with water |
| miscible | will mix with water at any proportion |
| Polar solvents | mix readily with water (alcohols) |
| LEL | lower explosive limit - lowest concentration of a combustible or flammable gas in air that will support combustion |
| UEL | upper explosive limit - highest concentration of a combustible or liquid gas in air that will support combustion |
| Explosive range/ignitable mixture | Range of vapor mixture that will ignite when subjects to an ignition source |
| Vapor density | density of gases in relation to air air=1 less than=rise (methane) great than=sinks(propane) |
| Oxidizer | any substance that yields oxygen during a chemical reaction |
| When a fire becomes ventilation controlled, the available air supply will determine: | the speed and extent of fire development and the direction of fire travel |
| Stages of fire development | Incipient, Growth, Fully Developed, Decay |
| Thermal layering | the tendency of gases to form into layers according to temperature |
| Describe a fully developed compartment fire (3 points) | - maximum amount of heat possible for available fuel and oxygen - fire is ventilation controlled - flammable products of combustion are likely to flow from the compartment of origin into adjacent compartments or through openings to the exterior |
| Flashover | very rapid transition from local burning of the contents within a compartment to widespread burning of all exposed fuel within that compartment |
| Backdraft | explosively rapid combustion of flammable gases - occurs in decay stage |
| Smoke explos | ignition of premixed pocket of fire gases and oxygen that may occur when an ignition source is introduced - can involve cold smoke |
| Highest plume temperatures will be found in: | corners |
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