Emergency responders spend considerable amounts of time preparing for fires, medical incidents, police calls and industrial accidents. They take courses in rescue, firefighting, medical treatment and law enforcement. A large number of emergency responses involve hazardous materials but many responders shy away from "hazmat," and "freak out" at any mention of the word chemistry! The reality, though, is this — you need a basic understanding of the physical and chemical characteristics of hazardous materials to deal with them effectively.
This is the first of a series of columns that will provide emergency response personnel with a view of chemistry as it applies to the hazardous materials encountered in daily responses. Some of the concepts presented here may bend the rules of chemistry a bit. However, the purpose of this approach is not to educate chemists but to teach response personnel about basic chemistry.
This study of chemistry for the purpose of hazmat response may be considered "street chemistry." The concepts presented work in the street application of chemistry when dealing with hazardous materials. This series gives fire, police, EMS and other emergency personnel some basic tools to better understand hazardous chemicals. The information may help keep you from being injured or killed at the scene of a hazmat incident.
Inorganic Vs. Organic
Chemistry is the study of matter. Most chemicals can be divided into two families: inorganic and organic. Acids, bases, salts and certain elements are some materials studied with inorganic chemistry. Organic chemistry is the study of compounds that all contain carbon and a few other elements such as oxygen, nitrogen, fluorine, chlorine and bromine.
Matter is defined as "anything that occupies space and has mass." Matter exists in three basic forms: solids, liquids and gases. Examples of hazardous materials in liquid form would be gasoline, alcohol and benzene. Among the gases are ammonia, propane and chlorine. Solids include phosphorus, ammonium nitrate and sodium peroxide.
Temperature and pressure have a bearing on the physical state of a chemical but do not change the chemical properties. Oxygen is a gas under normal temperatures and pressures. When oxygen is pressurized to a certain point and cooled by the ultimate release of pressure, it becomes a cryogenic liquid but maintains all of its chemical properties. Water is a liquid at normal temperatures and pressures but if exposed to temperatures below 32 degrees Fahrenheit it becomes a solid. The solid form of water maintains all of the chemical properties of liquid water. If water is heated above 212 degrees F, it becomes a gas but maintains all of the chemical properties of liquid water.
The hazard presented by a chemical may be affected by the physical state of the material when it is encountered. For example, only gases burn. Solids and liquids do not burn, even though they may be listed as flammable. A solid or liquid must be heated until it produces enough vapor to burn. Water has a cooling effect on the skin as a liquid but when it is turned into a gas, water causes burns to the skin.
There are some intermediate steps in the process of classifying solids, liquids and gases. Some solids may have varying particle sizes from large blocks to filings, chips and dusts. Particle sizes of vapors may vary from invisible vapors that are very small to mists and droplets that are readily visible.
The smallest part that an element can be divided into, by normal means, is an atom. Atoms of elements are chemically combined with atoms of other elements to form compounds. Dividing a compound into its smallest part would create a molecule. Molecules of compounds contain different types of atoms bonded together in fixed proportions.
The molecules of solids are packed together very closely in an organized pattern. Because the molecules are packed tightly together, they can vibrate only very gently in a very small space. This is why a solid maintains a definite size and shape until heated. When particles are this close together, they attract each other and it takes a lot of energy to pull them apart. When a solid is heated, the molecules start to vibrate faster and they eventually pull apart.
The molecules of a liquid are farther apart than those of a solid but are still attracted to each other. They are not arranged in a regular pattern. Liquids do not have a shape of their own so they conform to the shape of the container in which they are placed. When a liquid like gasoline is poured into a lawn mower engine fuel tank, it conforms to the shape of the tank. When gasoline is pumped into a gasoline tanker, it conforms to the shape of the tanker.
Molecules of a gas move rapidly and are not attracted to each other. Gases have no definite shape of their own and conform to the space or container in which they are placed. If a balloon is filled with helium, the helium takes on the shape of the balloon.
Chemical Properties
Hazardous materials may undergo both chemical and physical changes. A chemical change involves a reaction that alters the composition of the substance, and thereby its chemical identity. Chemical properties include: reactivity, stability, corrosivity, toxicity and oxidation potential.
New compounds may be formed which may have different characteristics than the compounds or elements used to make them up. Chlorine, for example, is a poison gas; sodium is a reactive metal. When they are combined, they form sodium chloride, which is neither a poison nor a reactive chemical it is table salt! Physical changes involve alterations of the physical state of the chemical but do not produce a new substance; for example, the physical transformation from a liquid to a gas or a liquid to a solid. Physical properties include: specific gravity, vapor pressure, boiling point, vapor density, melting point, solubility, flash point, fire point, autoignition temperature, flammable range, heat content, pH, and TLV and PEL.
The basics of chemistry cannot be discussed without looking at the Periodic Table of Elements. The properties of elements repeat in a regular way when the elements are arranged by increasing atomic number. This is known as periodicity.
The Periodic Table is chemistry's method of organizing everything that is known about the chemical universe on one piece of paper. The table reveals the relationship between elements by showing the tendency of their properties to repeat at regular intervals. All chemicals are derived from elements or combinations of elements from the periodic table.
Symbols are used on the table to represent each of the elements. The Periodic Table is composed of a series of blocks representing each element. Within each block is a symbol which represents the name of that element. The symbol is a type of shorthand for the element's name. For example, the element gold is represented by the symbol Au, chlorine is Cl and potassium is K. Each symbol represents one atom of that element. The symbols may be a single letter or two letters together. A single letter is always capitalized. When there are two letters, the first is capitalized and the second is always lowercase. This is important to understand when trying to identify elements and compounds. For example: CO is the molecular formula for the compound carbon monoxide; Co is the symbol for the element cobalt two totally different materials with quite different hazards.
The symbols and names of the elements are derived from a number of sources. They may have been named for the person who discovered the element. For example, the symbol for tungsten is W, for Wolfram, its discoverer. Other elements are named for famous scientists, universities, cities and states. Es is the symbol for Einsteinium, named for Albert Ein-stein. Cm is the symbol for Curium, named for Marie Curie. Bk is the symbol for Berkelium, named for the city of Berkeley, CA. Cf is the symbol for the element californium, named after the state of California. Other element names come from Latin, German, Greek, and English languages. Au, the symbol for gold, comes from aurum, meaning "shining down" in Latin. Cu (copper) is from the Latin cuprum or cyprium because the Roman source for copper was the island of Cyprus. Fe (iron) is from the Latin ferrum. Rubidium means red in color. Mercury is sometimes referred to as quicksilver. Sulfur is referred to as brimstone in the Bible.
There are 90 naturally occurring and 18 man-made elements. Not all of the elements on the Periodic Table are common or particularly hazardous to responders. There are, however, some that we will call the "Hazardous Materials Elements." These elements are particularly important when studying the chemistry of hazardous materials.
Most of the hazardous materials encountered by response personnel include or are produced from these 39 elements. Hazmat personnel should become familiar with these 39 elements and be able to recognize them by symbol and name. Formulas may appear on container labels and are found in many reference books and computer data bases. Being able to recognize symbols in a formula could help responders quickly identify potential hazards. This is especially true if part of a label is missing and only the formula is visible.
Elements with 83 or more protons are radioactive; many are rare and probably will not be encountered by emergency responders. Man-made elements are the result of nuclear reactions and research. These elements may have existed naturally on earth at one time but because they are radioactive and many half-lives have passed they no longer exist naturally.
The elements on the Periodic Table can be divided into three groups: primary, transition and rare earth. Primary elements have a definite number of electrons in the outer shell. This number is equal to the number at the top of each column in the "towers" at each end of the periodic table. Transition elements may have differing numbers of electrons in the outer shell. They are located in the "valley" between the towers. Horizontal rows are called periods and are numbered from 1 to 7. Atomic numbers increase by one as you go across the periods from left to right.
An element's atomic weight is listed on the Periodic Table. Atomic weight is the sum of the weight of the protons and the neutrons located in the nucleus of an atom. All of the weight of the element occurs in the nucleus. For the purposes of "street chemistry," electrons will not have weight. Atomic weights are located on the Periodic Table above or below the symbol of an element. It is the number that is not a whole number. Location of the atomic number varies among Periodic Tables, so be sure to look for the number with the decimal point.
The other number on the Periodic Table located above or below the symbol is a whole number and is known as the atomic number. The atomic number is equal to the number of protons in the nucleus. The atomic number also equals the total number of electrons in the orbits outside the nucleus of an atom. Protons have a positive charge (+) and electrons have a negative charge (-). There must be an equal number of protons and electrons in an atom of a particular element to maintain an electrical balance. An element is identified by the number of protons, which is the atomic number. The number of protons in an element does not change. If the number of protons is changed, the result is a different element. Protons act as a kind of "social security number" to identify a specific element.
The Periodic Table is divided into two sections by a stair-stepped line. This line starts under hydrogen and goes over to boron and then stair steps down one element at a time to astatine or radon, depending on which Periodic Table is being used. Eighty-one elements to the left and below the stair-stepped line are metals. Metals make up about 75 percent of all elements. Metals lose their outer shell electrons easily to the non-metals when forming compounds. They conduct heat and electricity very well, and are malleable (can be flattened) and ductile (can be drawn into a wire). Metals are all solids except for gallium, mercury, francium and cesium, which are liquids at "normal" conditions.
The 17 elements to the right and above the line are non-metals. Non-metals have a strong tendency to gain electrons when forming a chemical bond. They may be solids, liquids or gases, and are poor conductors of heat and electricity. Solid non-metals are either hard and brittle or soft and crumbly.
The numbers at the top of the vertical columns on the Periodic Table indicate the number of electrons in the outer shell of the elements in that column. The exception to this is the transition elements between the two towers on either end of the table. Unlike the primary elements, the numbers above the transition metal columns do not indicate the number of electrons in the outer shell of these elements. The transition elements can have differing numbers of electrons in their outer shells.
Vertical columns on the Periodic Table contain elements that have similar chemical characteristics in their pure elemental form. These elements have the same number of electrons in the outer shell. This is why they have similar chemical behaviors. These similar elements are sometimes referred to as families. Some of the more important families include: the alkali metals in column one, the alkaline earth metals in column two, the halogens in column seven, and the noble or inert gases in column eight.
The alkali metals in column one begin with lithium and continue through sodium, potassium, rubidium, cesium and francium, which are liquids at normal temperatures. The alkali metals are water reactive. They react violently with water, producing flammable hydrogen gas and enough heat to ignite the gas. These elements are so reactive that they do not exist in nature as the pure element. They are found as compounds of the metal such as potassium oxide and sodium chloride. Some isotopes of cesium and all isotopes of francium are radioactive. These elements are somewhat rare, so you are not likely to see them on the street.
The alkaline earth metals in column two are less reactive than the alkali metals in column one. Beryllium does not react with water at all. The others have varying reactions with water. Alkaline earth metals are all solids. They have to be burning or in a smaller physical form before they become water reactive. Magnesium, for example, is extremely water reactive when it is involved in fire. The application of water to a magnesium fire will cause violent explosions which can endanger responders. If it is necessary to fight fires involving magnesium, water should be applied from a safe distance with the use of unmanned appliances. Other elements in column two are also water reactive to varying degrees. These include calcium, strontium, barium and radium, which is radioactive.
The halogens in column seven are non-metals. They may be solids, liquids or gases. Fluorine and chlorine are gases at normal temperatures and pressures. Bromine is a liquid to 58 degrees Celsius and produces vapor rapidly when above that temperature. Iodine is a solid; astatine is a radioactive solid but you are not likely to encounter it. Halogens are all toxic and are strong oxidizers; fluorine is a much stronger oxidizer than oxygen. In fact, fluorine is the strongest oxidizer known.
In the pure elemental form, halogens do not burn but they will accelerate combustion much like oxygen because they are oxidizers. Some halogen compounds are components of fire extinguishing agents called halons. Halons are being phased out because of the damage they cause to the ozone layer of the earth's atmosphere.
Elements in column eight are all gases. They are non-flammable, non-toxic and non-reactive. Family eight elements are sometimes referred to as the inert or noble gases. Normally they do not react chemically with themselves or any other chemicals. Helium is used for weather balloons and airships. Neon is used for lighting and beacons. Argon is used in electric light bulbs. Krypton and xenon are used in special light bulb for miners and in light houses. Radon is radioactive and is used in tracing gas leaks and treating some forms of cancer.
The noble gases have a complete outer shell of electrons, two in helium and eight in the rest. It is because of the complete outer shell of electrons that the noble gases do not react chemically. All of the other elements on the periodic table try to reach the same stable electron configuration. The reason why chemical reactions occur is because the elements are trying to reach stability.
Column eight elements are all non-flammable and non-toxic gases. However, they can displace the oxygen in the air and cause asphyxiation inside of buildings or in confined spaces. Most of the noble gases are present in the air like nitrogen and oxygen. Inert gases are commonly shipped and stored as compressed gases or cryogenic liquids.
The Periodic Table can provide valuable assistance as another resource when trying to identify the hazards of chemicals. Chemistry topics to be discussed in the next article will include: Compounds and Mixtures, The Atom, Molecular Formulas and Chemical Bonding.
Robert Burke, a Firehouse® contributing editor, is a Fire Protection Specialist with the University of Maryland at Baltimore. He is a certified Hazardous Materials Specialist and has served on state and county hazardous materials response teams. Burke is a member of the Earleigh Heights, MD, Volunteer Fire Company and has 16 years' experience in career and volunteer fire departments, attaining the rank of assistant chief, as well as serving as a deputy state fire marshal. He holds a bachelor's degree in fire science and is an adjunct instructor at the National Fire Academy, Maryland Fire and Rescue Institute, and Delaware County, PA, Fire Academy. His book, Hazardous Materials Chemistry For Emergency Responders, was published in January 1997.
