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Temperature
A scale measure of heat energy and is key in determining how materials will react.
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Temperature can be measured in:
- Centigrade (also known as Celsius)
- Fahrenheit units
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Boiling Point
As the temperature of liquid increases, the molecules gain energy and, as a result, move around more. the most energized molecules rise to the top and they enter the air as vapor. ______ ________ of a liquid is affected by atmospheric pressure.
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Melting Point
the temperature at which a solid becomes a liquid. When this happens, the tightly compacted molecules of the substance gain energy. There is movement among the molecules as those with higher energy at the surface break away and enter the liquid state.
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Freezing Point
The _________ __________ is the temperature at which a liquid becomes a solid. At some temperature, unique to each substance, the rate of solid particles becoming liquid and the rate of liquid particles becoming solid is the same. That is, the melting point of a solid is the same as the freezing point of its liquid.
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Compressed Gases
Pressurized Liquefied
(Gaseous State) (liquid State)
"liquefied" cryogenic
Types of Compressed Gases
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Sublimation
A few solids can change directly to a gas without through a liquid state; this process is known as a ______________. carbon dioxide (dry ice) or moth balls (naphthalene) are examples of solids that ____________.
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Liquid
A __________ is a substance that flows easily and has a specific volume, but no specific shape. ___________ Molecules are not tightly bound together , allowing ______ to flow.
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Gas
A ______ is a substance that expands to fill any given volume, has no independent shape, and is readily compressed. _____ are the least dense of the three states.
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Vapor Pressure
A measure of the ability of a material to evaporate that is, change from a liquid state to a vapor or gaseous state. The higher the vapor pressure of a material, the faster it will evaporate.
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Water at 212F
= VP of 760 mm Hg - water rapidly evaporates at its boiling point
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Water at 122F
= VP of 93 mm Hg
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Water at room temperature
= VP of 25 mm Hg
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Acetylene gas
+ VP of approximately 2500 mm Hg (gas)
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Acetone
= VP of approximately 180 mm Hg on a warm day
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Water
VP = approximately 25 mm Hg (evaporates slowly)
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Most Solids
VP = near 0 mm Hg (do not evaporate)
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materials with VP greater than _______ atmospheric pressure (____ mm Hg) evaporate immediately and are gases
760
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Many ____________ pose the greatest hazard to health when they are in a gaseous or vapor state.
Liquids
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Flammable materials in a ______ or _________ state are more hazardous than those in _______ form because the vapor from a liquid burns and is more easily inhaled
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Vapor Density
The measure of the tendency to sink or rise
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Air has a vapor density of
1.0
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Vapors or gases with a vapor density greater than 1
tend to sink in air
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vapors or gases with a vapor density less than 1
tend to rise, such as methane with a vapor density of .55
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Vapors or gases with Vapor densities around 1.0 will be more influenced by _________ and ________________ then by their vapor densities
Wind conditions and temperature
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Flash Point
the minimum temperature of a liquid at which a spark or flame can cause an instantaneous flash in the vapor space above the liquid
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a flammable liquid, by NFPA definition, is a liquid that has a flash point below
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The United States Department of Transportation defines a flammable liquid as a liquid with a flash point below
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Liquid Flash Points of:
Gasoline
Acetone
Kerosene
- Gasoline -45 F
- Acetone 0 F
- Kerosene 150 to 185 F
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Generally liquids do not burn. Rather it is the ______ of flammable liquids that burn
vapors
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Determining ______________ is one consideration when confronted with a flammable liquid
how readily a liquid will vaporize
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Liquids that are classified ____________- or ___________ are often very toxic as well
Flammable or combustible
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Concentration
the term concentration refers to how much material there is in relation to another
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Percent (%)
parts per million (ppm)
parts per billion (ppb) are units used for:
measuring the concentration of gases and vapors in air
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Solids can be measured in terms of their weight
- grams (g)
- milligrams (mg =1/1000g)
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microgram
1 part per million 1/1,000,000g
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LEL - Lower Explosive (Flammable) Limit
UEL - Upper Explosive (Flammable) Limit
refer to
refer to the concentration of flammable liquid (in its vapor form) or a flammable gas in the air
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Below the LEL
the mixture is too lean to ignite
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Above the UEL
the mixture is too rich to ignite
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Between the LEL and UEL
the mixtures is said to be explosive or flammable
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Flammable Solids
materials that can ignite through friction, absorption of moisture, or chemical reaction
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Flammable solids are not classified as
Explosives
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Flammable solids ________ readily and _____ vigorously
ignite and burn
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Some flammable solids can ______ which means they can begin to burn without a flame or __________
- auto ignite
- other ignition source
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Pyrophoric solids spontaneously ignite in air
at or below 130 F
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Specific Gravity
the weight of a material compared to the weight of a reference substance, usually water, with a specific gravity of 1.0
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if a liquid or solid weighs more than water, it has a specific gravity....
greater than 1.0 and will sink in water
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materials with a specific gravity less than 1.0
will float on water
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solubility
refers to the degree that one substance will mix completely with another substance.
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the mixture of one substance with another is called
a solution
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Water Miscible
if a liquid mixes completely in a solvent, it is said to be miscible with that solvent.
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water Miscible
means that the liquid is infinitely soluble in water
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Polarity
results from an uneven distribution of positive (+) and negative (-) charges with a molecule
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regarding Polarity, molecules are
some are highly polar, sime nonpolar, and many have both polar and nonpolar parts
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Liquids whose molecules are polar (such as water and many alcohols)
dissolve when mixed with water
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nonpolar materials such as oils, gasoline, and other petroleum based products....
will not readily dissolve in water
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Adding Water to a nonpolar material, such as a gasoline....
will only spread the nonpolar molecules
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The pH scale
is used to determine whether a material is an acid or a base
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the pH sale ranges from
0 to 14 with 7 as a mid point
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Materials with a pH of 0 to 7
are considered acidic
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materials with a pH score of 7 to 14
are considered basic
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materials with a pH score of 7
are considered neutral
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the pH scale is a logarithmic scale which means
that since 7 is the center of the scale the difference between 6 and 7 is small but the difference between 3 and 4 is great and the difference between 1 and 2 is greater
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assign values to the pH scale
- start at 1 with 6 zeros count down to neutral
- start at 8 with 1 zero count up to 14
- Acidic from 1-6
- 7 neutral
- Basic from 8-14
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it is important to the difference between _________ and __________ in a corrosive
Concentration and strength
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Acids and Bases in water may be labeled according to:
- the concentration of the acid or base in water such as
- 40% sulfuric acid
- 98% potassium hydroxide
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highly concentrated solutions of any acid or base are likely
to be very corrosuve
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1) Air is assigned a vapor density of
1
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2) if a material is "water mincible", it is:
Infinitely soluble in water
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3) Substances with high vapor pressures are:
More likely to evaporate
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4) the rate of a chemical reaction cab usually be increased by:
Increasing temperature, concentration and pressure
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5) vapors and gases with molecular weights greater than 29 tend to:
Sink in air
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6) Although specific gravity has no unit of measure, it does have a value relative to:
the weight of water
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7) ignition temperature refers to:
The temperature at which a material burns without a flame
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8) a pyrophoric material describes a material that spontaneously ignites in air at or below:
130 F
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9) All gases have vapor pressures higher than:
760 mm Hg
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10) A chemicals explosive limit depends on its:
Concentration
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