Chapter 02-Fire Chemistry


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• Understand and explain the basic structure of atoms
• Explain how atomic structure determines the behavior of elements and compounds
• Understand basic chemical and physical properties and concepts and how they influence the behavior of materials involved in fires and hazardous materials incidents
• Correlate chemical structure with chemical names to allow for a general prediction of some hazardous chemical behaviors
• Understand key physical properties of chemicals and how these properties are related to fire protection

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Chapter 02-Fire Chemistry

  1. 1. Fire Chemistry Chapter 2
  2. 2. Objectives <ul><li>Understand and explain the basic structure of atoms </li></ul><ul><li>Explain how atomic structure determines the behavior of elements and compounds </li></ul><ul><li>Understand basic chemical and physical properties and concepts and how they influence the behavior of materials involved in fires and hazardous materials incidents </li></ul>
  3. 3. Objectives (cont’d.) <ul><li>Correlate chemical structure with chemical names to allow for a general prediction of some hazardous chemical behaviors </li></ul><ul><li>Understand key physical properties of chemicals and how these properties are related to fire protection </li></ul>
  4. 4. Introduction <ul><li>Gives basic information related to fires and chemicals that may be encountered by first responders </li></ul><ul><li>Understanding of these chemicals and their reactions during the fire combustion process is essential for the safety of firefighters </li></ul>
  5. 5. Matter <ul><li>Matter: </li></ul><ul><ul><li>Anything that occupies space and has mass </li></ul></ul><ul><ul><li>Something that occupies space and can be perceived by one or more of the senses </li></ul></ul><ul><li>Physical appearance or physical properties of matter: </li></ul><ul><ul><li>Mass, size, or volume </li></ul></ul><ul><li>Three states of matter: </li></ul><ul><ul><li>Solid, liquid, or gas </li></ul></ul>
  6. 6. States of Matter <ul><li>Solids </li></ul><ul><ul><li>Consist of a portion of matter having definite volume and definite shape </li></ul></ul><ul><li>Liquids </li></ul><ul><ul><li>Have definite volume but not definite shape </li></ul></ul><ul><ul><li>Will take on the shape of the vessel in which it is contained </li></ul></ul><ul><ul><li>Generally turn to gas when exposed to the atmosphere or when placed under pressure and heat </li></ul></ul>
  7. 7. States of Matter (cont’d.) <ul><li>Gases </li></ul><ul><ul><li>Have neither definite shape nor volume </li></ul></ul><ul><ul><li>Shape determined by amount of pressure placed upon it and shape of the container </li></ul></ul><ul><ul><li>Flammable gas: one that is flammable at atmospheric temperature and pressure within a mixture with air of 13% or less or it has a flammable range with air of more than 12% </li></ul></ul>
  8. 8. Chemical Properties of Matter <ul><li>All materials either inorganic or organic </li></ul><ul><ul><li>Inorganic </li></ul></ul><ul><ul><ul><li>Chiefly composed of earth minerals like rocks, soil, air, water, and minerals in or below earth’s surface </li></ul></ul></ul><ul><ul><ul><li>Majority not involved in the combustion process </li></ul></ul></ul><ul><ul><li>Organic </li></ul></ul><ul><ul><ul><li>Generally found in once living organisms </li></ul></ul></ul><ul><ul><ul><li>Consist of carbon, hydrogen, and oxygen </li></ul></ul></ul>
  9. 9. Cells <ul><li>Tiny mass of protoplasm usually containing a nucleus </li></ul><ul><li>Smallest structural unit of living matter </li></ul><ul><li>Capable of functioning independently </li></ul><ul><li>Make up organs of human body </li></ul><ul><li>Organic chemistry important to firefighters for understanding fire behavior and understanding the functioning of human body </li></ul>
  10. 10. Compounds <ul><li>Substance formed from two or more elements joined with a fixed ratio </li></ul><ul><li>Consists of chemically combined molecules </li></ul><ul><ul><li>Homogeneous </li></ul></ul><ul><ul><li>Have a definite composition regardless of origin, location, size, or shape </li></ul></ul><ul><ul><li>Elements cannot be separated by physical means </li></ul></ul><ul><li>Approximately five million identified </li></ul>
  11. 11. Structure of Molecules Figure 2-1 Wood subdivided into the cell, molecules, and compounds.
  12. 12. Atoms <ul><li>Basic building blocks of matter </li></ul><ul><li>Smallest unit of an element taking part in chemical reaction </li></ul><ul><li>Atoms of most elements can combine with others to form molecules by chemical interaction </li></ul><ul><ul><li>Example: water (H 2 O) is made up of two atoms of hydrogen and one atom of oxygen </li></ul></ul>
  13. 13. Structure of the Atom <ul><li>Consist of three types of subatomic particles </li></ul><ul><ul><li>Nucleus is in center of atom and contains two kinds of particles </li></ul></ul><ul><ul><ul><li>Neutrons: heavy with no electrical charge </li></ul></ul></ul><ul><ul><ul><li>Protons: equal in weight to the neutron and contains a positive electrical charge </li></ul></ul></ul><ul><ul><li>Orbiting around the nucleus are the third particles </li></ul></ul><ul><ul><ul><li>Electrons: light and carry a negative charge </li></ul></ul></ul>
  14. 14. Combination of Atoms <ul><li>109 elements </li></ul><ul><li>Atoms combine with other atoms to fill outer electron shells, or rid themselves of extra electrons </li></ul><ul><li>Atoms can have as many as one hundred or more electrons </li></ul><ul><li>Atom’s behavior can be determined by the number of electrons in the outer shell </li></ul>
  15. 15. Elements <ul><li>Basic construction materials of matter </li></ul><ul><li>Simplest form of matter </li></ul><ul><li>Can be grouped into families </li></ul><ul><ul><li>Halogenated: any chemical reaction in which one or more halogen atoms are incorporated into a compound </li></ul></ul>
  16. 16. Element Symbols <ul><li>Each chemical given a symbol, either a one or two letter abbreviation made up of a letter or letter in their name </li></ul><ul><li>Firefighters’ knowledge of these symbols and chemical formulas may be helpful dealing with situations </li></ul>
  17. 17. Molecules <ul><li>Smallest part of a pure chemical substance that has all properties of the material. </li></ul><ul><li>In constant motion, speed depending on its state </li></ul><ul><li>Physical change: molecules remain intact </li></ul><ul><li>Chemical change: molecules are altered </li></ul>
  18. 18. Mixtures <ul><li>A combination of substances held together by physical rather than chemical means </li></ul><ul><li>Ingredients of a mixture retain their own properties </li></ul><ul><li>Substance does not change in the formation of the mixture </li></ul>
  19. 19. Prefixes and Suffixes <ul><li>Pre-fixes are syllables added to the beginning of a word </li></ul><ul><li>Suffixes are syllables added to the end of a word </li></ul><ul><ul><li>Describe atoms that are added to a basic molecule </li></ul></ul><ul><ul><li>Denote groups of atoms added and behave as groups called functional groups </li></ul></ul><ul><li>In firefighting, used as identifiers to provide a warning </li></ul>
  20. 20. Organic Chemicals <ul><li>Contain some form of hydrocarbons or combination of carbon and hydrogen molecules </li></ul><ul><li>Number of carbon atoms that combine with number of hydrogen atoms determine the properties and reaction of the substance </li></ul><ul><li>Organic peroxides can react explosively in the combustion process </li></ul>
  21. 21. Properties of Chemicals <ul><li>Atoms of a certain element have the same properties </li></ul><ul><li>Properties make their behavior predictable, a valuable tool for firefighters when working with hazardous chemicals </li></ul><ul><li>Atoms combine to create a chemical compound </li></ul><ul><li>Defining characteristic of compounds are chemical formulas </li></ul>
  22. 22. Boiling Point <ul><li>Several definitions of BP </li></ul><ul><ul><li>Temperature that the vapor pressure of liquid equals pressure of the atmosphere around it </li></ul></ul><ul><ul><li>Temperature at which molecules in liquid are heated until it begins to bubble and changes to vapor </li></ul></ul><ul><li>Once started, as long as heat is applied, boiling continues and changes to vapor </li></ul>
  23. 23. Vapor Pressure <ul><li>Pressure placed on inside of closed container by vapor or molecules driven off the flammable liquid in space above the liquid </li></ul><ul><ul><li>Open cup test measures release of the vapors in terms of the pressure exerted at specific temperature </li></ul></ul><ul><ul><li>Closed cup test done by placing a lid on the cup containing liquid and taking pressure reading when vapors are released from it </li></ul></ul>
  24. 24. Vapor Density <ul><li>Mass of the vapor divided by the volume it fills </li></ul><ul><li>Carbon dioxide is 1.5 times as heavy as air </li></ul><ul><ul><li>Room filled with carbon dioxide will eventually blanket room with vapors at the floor level </li></ul></ul><ul><ul><li>Oxygen in the room will be replaced or forced upward </li></ul></ul><ul><li>Butane gas is twice as heavy as air and has flammability range of 1.9% to 8.5% </li></ul><ul><ul><li>Flammable vapors heavier than air may pool at lowest point awaiting a source of ignition </li></ul></ul>
  25. 25. Solubility <ul><li>Solubility in water indicates amount of a material that will dissolve and mix in water </li></ul><ul><ul><li>Materials that are soluble in water are polar solvents </li></ul></ul><ul><li>Insoluble or slightly soluble materials will form a separate layer and will either float or sink depending on specific gravity </li></ul>
  26. 26. Specific Gravity (Water and Air) <ul><li>Density of the product divided by the density of water or air </li></ul><ul><li>Water and air, the standards, are given the value of 1.0 at a certain temperature </li></ul><ul><li>Specific gravity provides insight for firefighters to determine: </li></ul><ul><ul><li>Best method of fire extinguishment </li></ul></ul><ul><ul><li>Best means of moving gas to the open environment </li></ul></ul>
  27. 27. Flash Point and Fire Point <ul><li>Flash point is minimum liquid temperature at which enough vapors are present above liquid to ignite or flash but does not continue to burn </li></ul><ul><li>Fire point is lowest temperature at which liquid produces vapor that can sustain continuous flame </li></ul>
  28. 28. Explosive Limits and Range <ul><li>Explosive range is range of concentrations of the materials in the air, which permit the material to burn </li></ul><ul><li>Lower explosive limit is lowest ignitable concentration of a substance in air </li></ul><ul><li>Upper explosive limit is highest percentage of a substance in air that will ignite </li></ul><ul><li>See Table 2-5 for list of gases and their limits </li></ul>
  29. 29. Hydrogen Ion Concentration (pH) Figure 2-2 pH values of common substances
  30. 30. Appearance and Odor <ul><li>Important in the description of material, including its color, smell, and physical state at normal temperature and pressure. </li></ul><ul><li>If all properties are carefully considered, it is impossible to find two chemicals with identical properties </li></ul>
  31. 31. Physical State <ul><li>Physical states of hazardous materials </li></ul><ul><ul><li>Liquids, solids, gases, sludge </li></ul></ul><ul><li>Boyle’s law: the more gas is compressed, the more it becomes difficult to compress further </li></ul><ul><li>Charles’s law: gas will expand or contract in proportion to an increase or decrease in temperature </li></ul><ul><li>Special conditions </li></ul><ul><ul><li>Sublimation, compressed gases, cryogenic liquids </li></ul></ul>
  32. 32. Changes in Physical State <ul><li>Chemical reactions occurring during leak or fire cause change in physical state </li></ul><ul><li>Leaking liquid may change to the gas form with increase in volume </li></ul><ul><li>In vapor form, it may pool in lower areas or ascend depending upon its specific gravity </li></ul>
  33. 33. Combustible Dusts <ul><li>Materials in solid form can be made to combust or explode by converting them into dust </li></ul><ul><li>Any organic dust can explode </li></ul><ul><li>Many dust explosions occur in pairs </li></ul><ul><li>Many metals in a dust or shavings form will also explode </li></ul>
  34. 34. Boiling Liquid Expanding Vapor Explosion <ul><li>Occurs when a pressure tank has its container metal softened or weakened by heat or corrosio n </li></ul>Figure 2-3 BLEVE.
  35. 35. Chemical Reactions <ul><li>Endothermic: type of reaction in which energy is absorbed when the reaction takes place </li></ul><ul><li>Exothermic: type of reaction that will release or give off energy </li></ul><ul><li>Polymerize: the process in which molecules of a monomer are made to combine with other monomers </li></ul>
  36. 36. Water-reactive Materials <ul><li>Water-reactive materials react with water, often violently, to release heat, a flammable or toxic gas, or a combination of the two </li></ul>Figure 2-6 Magnesium reacting to firefighters’ hose line
  37. 37. Air-reactive Materials <ul><li>Reactive simply in presence of air when they escape their containers </li></ul><ul><li>Some will ignite in air </li></ul><ul><ul><li>Potassium metal is an example </li></ul></ul><ul><ul><li>Air-reactive white phosphorous must be stored underwater to prevent its ignition </li></ul></ul>
  38. 38. Oxidizers <ul><li>Oxidizers (oxidizing agents) </li></ul><ul><ul><li>Present special hazards because they react chemically with a large number of combustible organic materials </li></ul></ul><ul><ul><ul><li>Oils, greases, solvents, paper cloth, and wood </li></ul></ul></ul><ul><ul><li>Some inorganic peroxides are very reactive and sensitive to shock </li></ul></ul><ul><ul><li>Other commonly encountered oxidizers: </li></ul></ul><ul><ul><ul><li>Ammonium nitrate (see Figure 2-7), potassium permanganate, ammonium persulfate, sodium nitrate </li></ul></ul></ul>
  39. 39. Figure 2-7 Federal building, Oklahoma City, Oklahoma
  40. 40. Unstable Materials <ul><li>When exposed to water, air shock or pressure materials designated as unstable can decompose, polymerize, or become self-reactive </li></ul><ul><ul><li>Monomers: building blocks that form many types of polymers </li></ul></ul><ul><ul><ul><li>Spray foam insulation, which is sold in an aerosol container at most hardware stores </li></ul></ul></ul><ul><ul><li>Once started, the reaction cannot be stopped </li></ul></ul>
  41. 41. Incompatible Materials <ul><li>When some materials are mixed with others, they can adversely affect human health and the environment: </li></ul><ul><ul><li>Generation of heat </li></ul></ul><ul><ul><li>Violent reaction </li></ul></ul><ul><ul><li>Formation of toxic fumes or gases </li></ul></ul><ul><ul><li>Formation of flammable gas </li></ul></ul><ul><ul><li>Fire or explosion </li></ul></ul><ul><ul><li>Release of toxic substances if they burn or explode </li></ul></ul>
  42. 42. Catalyst <ul><li>A catalyst is a substance that is not created or destroyed in chemical reaction, but greatly affects the rate of reaction </li></ul><ul><ul><li>Example: platinum, used in the catalytic converter of a car exhaust system, causes the fuel to burn faster and cleaner without consuming the platinum </li></ul></ul>
  43. 43. Toxic Combustion Products <ul><li>Formation depends upon the nature of the burning material and the amount of oxygen present </li></ul><ul><ul><li>Many home furnishings and decorations made with plastics that when exposed to fire release toxic chemicals into the atmosphere </li></ul></ul><ul><li>Self-contained breathing apparatus (SCBAs) are used to avoid inhaling this toxic material </li></ul>
  44. 44. Summary <ul><li>Basic chemistry and physical processes are important to firefighters for emergency response actions and their safety </li></ul><ul><li>Firefighters must be equipped with knowledge and tools to investigate and determine the extent of the hazard </li></ul><ul><li>Once the hazard is identified, firefighters can actively take action required to control and mitigate the situation </li></ul>