UNIT I STUDY GUIDE/Introduction to Chemistry

Course Learning Outcomes for Unit I

Upon completion of this unit, students should be able to:

1. Recognize how to use basic chemistry fundamentals that are essential in the study of hazardous materials, such as the common elements by their atomic symbols on the periodic table; the difference between elements, compounds, and mixtures; how ionic and covalent bonding influence chemical properties; and properties of gases, liquids, and solids.
1.1 Use the periodic table to identify the symbols, atomic number, atomic weights, and general properties of currently known elements.
1.2 Differentiate between elements, compounds, and mixtures; ionic and covalent bonding; and physical and chemical changes or properties.
1.3 Explain the properties of gases, liquids, and solids.
1.4 Determine chemical formulas and molecular weights of compounds.
1.5 Recognize heat of chemical reactions and how it relates to the transfer of energy.

2. Identify the common units of measurement used in the practice of environmental health and safety (EHS) and fire science (FS), such as concentration, temperature, and pressure.
2.1 Identify the common units of measuring scientific property or behavior, and convert between units of the same kind (measure the same property).
2.2 Apply the concepts of concentration, density, specific gravity, vapor density, vapor pressure, and heat/energy.

9. Demonstrate familiarity with the Global Harmonized System of Classification and Labeling of Chemical Substances (GHS) and the NFPA system of identifying potential hazards.
9.1 Describe the GHS system.
9.2 Identify the types of hazardous materials represented by the GHS pictograms.
9.3 Describe the NFPA system of identifying potential hazards.

Reading Assignment

Chapter 1:
Introduction

Chapter 2:
Some Features of Matter and Energy

Chapter 4:
Chemical Forms of Matter

Unit Lesson

Hazardous materials, now commonly known as hazmat, are present in all facets of life. They can be found at home, in the workplace, in public places, at shopping malls, and even at amusement parks. The Merriam- Webster Online dictionary (n.d.) defines hazmat as, ?a material (flammable or poisonous material) that would be a danger to life or to the environment if released without precautions? (para. 1). Hazardous materials are important for the continued operations of our technology-based society (Meyer, 2014). They have a purpose but can be harmful if not handled properly. In order to minimize hazards posed by these materials, their storage, transport, use, and disposal are heavily regulated by various federal, state, and local agencies.
Despite the myriad regulations, incidents still occur that need to be mitigated for the protection of public health and the environment.

Hazardous materials are generally classified into the following categories: corrosive (acids/bases), water- reactive, air-reactive (pyrophoric), flammable, toxic, explosive, and radioactive. In this course, we will study their chemical behavior, properties, and interactions with each other so that we can learn to manage them properly and/or be able to respond and mitigate incidents involving them in a safe and timely manner. Most of the materials in our textbook are viewed from the fire-service perspective; however, the chemistry will apply across the parameters and responsibilities of occupational safety and health as well as environmental management professionals.

Before we get into specifics regarding hazardous materials, we will first review some basic chemistry fundamentals that are essential to better understand the various topics covered in this course. Due to time constraints, only a few selected topics from Chapters 1, 2, and 4 will be covered in this unit (Unit 1). Students, however, are encouraged to read all of Chapters 1 through 5 if they need to refresh their knowledge or understanding of chemistry fundamentals.

Periodic Table: Everybody must have heard of the periodic table at least once before this class. This table is where all the known chemical elements are arranged in groups and periods based on their currently known properties. A copy of a modern version of this table is included as Figure 4.3 on page 115 of our textbook. As you can see, the chemical symbols, atomic number, and weights are included in the table. It is advisable to memorize the symbols of at least the common elements if you are not already familiar with them.

An element is defined as a substance that is composed of only one kind of an atom; therefore, it cannot be broken down into a simpler substance by chemical means (Fire, 1996). An atom, as you may know, is the smallest particle of an element and is composed of electrons, protons, and neutrons as shown in the illustration below.

Meyer (2014) defines atomic number as the number of protons in an atom, while atomic weight represents an abundance-weighted sum of the atomic masses of an element?s naturally occurring isotopes from a specified source. In practice, we use the atomic weights to get the formula or molecular weights of a chemical compound. Molecular weight is an important chemical property because it is used in determining other properties such as density. An example of how to calculate the molecular weight is presented in Section 4.16 (page 130).

A substance is any homogeneous material that has a constant and fixed chemical composition. An element and a compound are substances. When the material is not a pure substance, it is called a mixture.

Back to the periodic table, on the version included in the textbook, each column represents a family of elements. Each column or family (also called group) is identified by a number and capital letter, such as IA, 2A, 3B, up to 8A. Another version of the periodic table, which will not be discussed here, numbers these columns consecutively, 1 through 18, from left to right (Meyer, 2014). One use of the periodic table is by just looking where the elements are located, we can readily tell their general properties. For example, lithium, in general has similar chemical properties (water-reactive) as sodium since they both belong to the same family (they are relatives). One popular family/group that is encountered in the field of hazardous materials is the halogen family (Group 7A). This family consists of chlorine, bromine, fluorine, iodine, and astatine; each of them are very reactive (you can now add astatine in your vocabulary). The horizontal row in the table is called a period. In each period, the elements are arranged from left to right in the order of their increasing atomic number.

Ionic and Covalent Bonding: Two or more elements can combine to form a chemical compound. An example of a compound is table salt, sodium chloride (NaCl), which is made by combining sodium metal (Na)

and yellow chlorine gas (Cl2). These compounds are formed or joined by a force that chemists refer to as a chemical bond, meaning that the atoms of the combining elements get attached to each other. Chemical bonding could be an ionic or covalent bonding, depending on the number of electrons in the outer shell of each atom. (Note: The difference in outer shell electron configurations is beyond what you need to understand for this course.)

An example of ionic bonding is that of sodium fluoride (NaF) as illustrated on page 119. An example of covalent bonding is that of methane (CH4) as illustrated on page 120. Compounds formed by ionic bonds are called ionic compounds and those formed by covalent bonds are called covalent compounds. Note that these compounds have contrasting general properties, which are summarized in Table 4.6. For example, ionic compounds generally have higher boiling points, are nonflammable, and are more soluble in water (Meyer, 2014).

Solids, liquids, and gases: After chemical bonding, the resulting material (compound) takes on a certain physical form or state (Schnepp & Gantt, 1998). The three main states (of matter) are solid, liquid, and gas. Basically, a solid has a definite shape and volume, while a liquid has volume but has no shape. A gas has neither. A
vapor, according to Meyer (2014), is the gaseous form of a substance that exists as a solid or liquid at normal ambient temperature. Although not encountered in the study of hazmat, it is interesting to note that there are two other forms of matter: namely, plasma and Base-Einstein condensate (Meyer, 2014). These two will not be discussed in this course. However, the physical state is important when it comes to handling and/or remediating hazardous material incident sites. It also impacts the level of protection needed as their behavior is influenced by their state or form.

Physical and chemical properties: When an element or a compound gets transformed but the chemical composition is not changed, the process involves only a physical change (e.g., boiling, freezing, pulverizing). The behavior that the substance exhibits during the physical change is its physical property (boiling point, freezing point, or temperature). The substance is still the same.

By contrast, if the process results in a change in the chemical composition, then it is considered a chemical change/reaction. Examples of this are combustion and corrosion. Similarly, the associated properties when undergoing a chemical change are chemical properties. In the combustion example, one or more new substances are formed as a result of the burning process.

Units of measurement: We cannot learn chemistry without understanding some basic math (addition, subtraction, multiplication, and division). A scientific observation (measurement) must consist of a number and a scale (unit) for the measurement to be meaningful (Zumdahl & Zumdahl, 2000). There are two systems of units that are being used today: the metric system (SI) and the English (U.S.) system. Units of the same kind can be converted from one system to the other by using the factor-unit method. See pages 41-42 for examples. It is more efficient for you to use a conversion Website, but it is good to practice manually converting between basic units to improve your understanding and familiarity with the factor-unit method. In our field, this is very important, and there may be times when there is no Internet access.

Concentration: This is the amount of a substance present in a given mass or volume of a mixture. Examples of units of concentration include the following:

? airborne concentration of contaminants in the air in a room: milligrams/cubic meter (mg/m3),
? concentration of a constituent such as sulfates in liquid samples like water: milligrams/liter (mg/L),
? concentration of a constituent such as arsenic in solid media like soil samples: milligrams/kilogram (mg/kg), and
? can also be expressed in % by mass or volume.

Side note: This is not in the textbook, but it may be useful to some, especially if taking the CSPs and IH
exams:

Conversion of ppm to mg/m3 and vice versa: ppm =

(????/??3)(24.45),
????

where 24.45 is volume in liters of one gram-mole of a substance.

Specific terminology is also beneficial in studying hazardous materials. Density is the mass of a substance divided by the volume that it occupies. Examples of units of density include the following: pound/gallon

(lb/gal); pound/cubic feet (lb/ft3); and kilogram/cubic meter (kg/m3). Specific gravity is the mass of a given volume of matter compared with the mass of an equal volume of water; this is dimensionless (mass to mass). Vapor density is the mass of a vapor or gas compared with the mass of an equal volume of another gas such as air at the same temperature and pressure, this is also dimensionless (mass to mass). Temperature is a measurement of how hot or cold; common units are Celsius and Fahrenheit. Pressure is the force applied to a unit area (e.g., pounds/square inch lb/in2 or psi). Heat is the form of energy transferred from one body to another because of temperature difference; energy due to atomic or molecular motion in a chemical. Heat is transferred by conduction, convection, and radiation.

Leave a Reply

Your email address will not be published. Required fields are marked *