Chapter 2 Flashcards
What is the definition of Physical Changes?
A transformation in which a material changes its state of matter (ex. from a liquid to a solid)
(CHIEF CONCEPT) What is an important first step in understanding that hazards associated with any chemical?
Identifying the State of Matter, defining whether the substance is a solid, liquid or a gas
The State of Matter is
The physical state of the substance. A solid, liquid or a gas.
What is a critical step in comprehending the nature of a release?
Identifying the reason(s) why the container failed
What does BLEVE stand for?
Boiling Liquid Expanding Vapor Explosion
What is a BLEVE
Occurs when a pressurized liquefied materials inside a closed vessel are exposed to a source of high heat. Occurs if relief valve can’t contain the increased pressure.
What is expansion ratio?
The volume increase that occurs when a compressed liquefied gas material changes to a gas
What is chemical reactivity (chemical change)?
The ability of a substance to undergo a transformation at the molecular level, usually with a release of some form of energy
(CHIEF CONCEPTS) What are the critical characteristics of flammable liquids?
- Flash Point
- Ignition Temperature
- Flammable Range
What is flash point?
The minimum temperature at which a liquid or a solid releases sufficient vapor to form an ignitable mixture with air.
What is ignition temperature (autoignition)?
The minimum temperature at which a fuel, when heated, will ignite in the presence of air and continue to burn. The ignition temperature for gasoline is 475 Fahrenheit.
True or False: When a liquid fuel is heated beyond it’s initial ignition temperature, it will ignite without an external ignition source
True (ex. a pan full of cooking oil)
What is flammable range?
A fuel/air mixture, defined by upper and lower limits that reflects an amount of flammable vapor mixed with a given volume of air.
What is the flammable range of gasoline vapors?
1.4% to 7.6%
(TEST) What is a lower explosive limit (LEL)?
The minimum amount of gaseous fuel that must be present for the air/fuel mixture to be flammable/explosive
(TEST) What is an upper explosive limit (UEL)?
The maximum amount of gaseous fuel that can be present for the fuel/air mixture to be flammable/explosive
True or False: If a fuel/air mixture falls between the UEL and LEL, an ignition source is still needed for a flash fire to occur
True
True or False: The wider the flammable range, the more dangerous the material
True. Hydrogen is 4.0% to 75%, natural gas is 5% to 15%, and propane is 2.5% to 9.0%
What is vapor pressure?
The pressure associated with liquids held inside any type of closed container
What is the key point to understanding vapor pressure?
The vapor pressure released from the surface of any liquid needs to be contained in order to exert pressure
How is vapor pressure expressed?
In PSI, atmospheres (atm), torr, millimeters of mercury (mm Hg), or bar
What is boiling point?
Temperature at which a liquid will continually give off vapors and if boiling long enough, will turn completely into gas.
What is the boiling point of water?
212 F
What is fire point?
The temperature at which sustained combustion will occur.