Course Learning Outcomes for Unit II Upon completion of this unit, students should be able to:
1. Detail the physical properties of the three states of matter. 1.1 Explain why radiative, conductive, and convective heat transfer in fires is especially important. 1.2 Describe the difference between thermally thin and thermally thick materials related to heat
conduction and radiation. 1.3 Explain how the methods of heat transfer create issues in firefighting with the development and
movement of fire.
Course/Unit Learning Outcomes
Learning Activity
1.1
Unit Lesson Chapter 4 Chapter 5 Unit II Essay
1.2
Unit Lesson Chapter 4 Chapter 5 Unit II Essay
1.3
Unit Lesson Chapter 4 Chapter 5 Unit II Essay
Required Unit Resources Chapter 4: Flow of Fluids Chapter 5: Heat Transfer
Unit Lesson Review In the previous unit, we covered the concepts associated with the dynamics of fire and the outcome of combustible reactions being determined by thermodynamics. In addition, we understood the lack of preparedness was cited for firefighter injuries and fatalities. Several authors suggested it was the result of the attitudes and behavior of firefighters over simplifying fire behavior and combustion (Gann & Friedman, 2015). In the lesson, we covered the main constituents in fire growth, learning the rate at which fire will spread over adjacent combustible materials is affected by mass, energy, heat, and enthalpy. We learned an enthalpy flow is from one point to another because of a temperature difference. We understood that fire starts at the boundary where vaporization of a liquid turns into a volatile gas mixing with air (oxygen) reaching a continuous state resulting in combustion (Figure 1). The sauce pan will absorb some energy by the layer of
UNIT II STUDY GUIDE
Three States of Matter
FIR 2303, Fire Behavior and Combustion 2
UNIT x STUDY GUIDE
Title
volatiles above the surface of the cooking oil. Then convective and conductive heat exchange occurs above including the volatile gas. We understood that combustion, as a negative enthalpy reaction, is an exothermic chemical reaction between a fuel and an oxidizer resulting in the generation of substantive heat and light (Gann & Friedman, 2015). We saw an explanation of enthalpy reaction where cooking oil, as a liquid, became vaporized and, as it burned, suspended solids in smoke resulting in flammable, volatile mass of solids and aerosols (Figure 2 and Figure 3).
Combustion, according to these authors, always involves oxidation at the molecular level. In this unit, we will cover the three states of matter. Three States of Matter Matter is found in three states: solid, liquid, and gas (Gann & Friedman, 2015). As firefighters, when we enter a structure fire, we see matter in the form of physical material all around us. Some of the physical material undergoes a chemical reaction producing intense heat and light through a process of enthalpy. If there are three states of matter, is fire a solid, a liquid, or a gas? Is there a physical and chemical change with matter? What are the phase changes related to fire?
Fire has a significant effect on matter or structure. As reviewed in Unit I’s Points to Ponder–Building on the Scenario, the structure fire resulted from a sauce pan with cooking oil (liquid matter) left unattended on the stove. The fire grew to one or two rooms (solid matter) being involved. One reason the fire grew rapidly is the characteristic of the matter in the compartment (rooms) enclosed the flames. We saw the heat generation and the nature of combustion products in Figure 2 as the fire transitioned during the growth of the fire to the fully developed phase in the one or two rooms of the apartment. The fire was spreading with turbulent smoke. How was the fire transmitted from the different states of matter? As firefighters, do we really care about the conductivity of materials regarding heat or even if heat remains at a uniform temperature as it is transmitted across the different materials (matter) and its thickness? When we advance handlines down the hallway, do we see the conductivity of solid materials and how fast the heat flows through it using radiant exposure equations (Figure 4)? Is it even important to a firefighter? Several years ago, experienced fire tacticians focused on the temperatures involved in structure fires due to the assigned rating of the personal protective equipment and not on the transfer of heat from one matter to another (International Fire Service Training Association [IFSTA], 2013). They based this on the color, volume, velocity, and density of smoke as an indicator of the estimated temperature. After all, are we only concerned with reading smoke?
Figure 1
Figure 3 Figure 2
