CHM 1020 chapter 6

A fuel is any
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Terms in this set (97)
A fuel is any
solid, liquid, or gaseous substance that may be combusted (burned) to produce heat or work
A fuel is considered valuable if it ignites easily at a
low temperature and produces a large quantity of heat during its combustion
Fuels should be
inexpensively isolated and have properties that allow for their safe and efficient storage or transport
A desirable fuel should leave
little residue behind after being burned, and should produce by-products that are not harmful to human health or the environment
Humans currently use coal, petroleum products (e.g., gasoline, diesel, propane), and natural gas as our primary
sources of fuel
The process of decaying matter
releases and reverses this process, producing CO2 and H2O. however, under certain conditions, the carbon-containing compounds that make up the organism only partially decompose
Over geological periods of time-millions and millions of years-changes in
temperature and pressure transformed dead plants and animal life into valuable forms, such as coal or crude oil
Considering how long it takes to convert plant life to fossil fuels, the rate at which we are burning coal, petroleum, and natural gas is
not sustainable-at least in terms of having enough of it available to meet current and future energy needs
Burning fossil fuels for energy fails to meet the criteria of sustainability in two ways
1) the fuels themselves are nonrenewable

2) the waste of combustion have adverse effects on our environment, both today and in the future
There are three necessary requirements to generate a fire-a source of heat, a fuel, and an oxidizer. When these components are combined, a
chemical reaction takes place that releases a variety of by-products and a significant amount of heat
Inadvertently opening a door and exposing the dying fire to a fresh source of oxygen results in a dangerously explosive situation, referred to as abackdraftThe oxygen in our atmosphere is the most typicaloxidizing agentAlthough much less common, it is also possible to have a combustion reaction with a ___ serving as the oxidizing agenthalogenThe great majority of fuels are hydrocarbons, compounds composed only of the element hydrogen and carbon1) one is the octet rule 2) another rule is that carbon forms four bonds in hydrocarbonsIf a pure hydrocarbon fuel is burned, the only product that will be generated upon complete combustion arecarbon dioxide and water vaporThere may also be some carbon monoxide and/or carbon soot generated due toincomplete combustionTo convey the same information more compactly, condensed structural formulas are often used in which some bonds arenot showntrue or false: Hydrocarbons follow a very different set of naming rules from inorganic compounds introduced in previous chapterstruefor structural formulas: For these compounds, a prefix indicates thethe number of carbon atoms are present in its structurefor structural formulas: Just as mono-, di-, tri-, and tetra- prefixes are used to count, so aremeth-, eth-, prop-, and but-for structural formulas: Prefixes are very versatile. They can be used not only at thebeginning of chemical names, but also within them to represent groups of chains or carbon and hydrogen atomsfor structural formulas: The suffix tells us something specific about theratio of carbon atoms to hydrogen atoms in the moleculeEnergy is a fundamental property of our universe, referring to the ability capacity ofmatter to do work or to produce changeThere are two general types (forms) of energykinetic and potential energykinetic energy the energy ofmotion, which includes the movement of atoms and molecules, as well as our activities such as walking, climbing, or runningpotential energy isstored energy, or the energy of position; that is, position with respect to another objectDuring combustion reactions, the relative positions of the atoms in the fuelchange, which alters its potential energyDuring combustion, the energy stored in the fuel molecules isconverted into heat, a form of kinetic energyThe first law of thermodynamics, also called the law of conservation of energy, states thatenergy is neither created or destroyedHeat is thekinetic energy that flows from a hotter object to a colder oneTemperature is a measure of the averagekinetic energy of the atoms and/or molecules present in a substancetrue or false: An object is "cold" when its atoms and molecules move more slowly, on average, relative to an object that is "warm." therefore, for the temperature of an object to increase, the kinetic energy of its atoms and molecules must increasetrueThe calorie (cal) was defined as the amount ofheat necessary to raise the temperature of one gram of water by one degree CelsisusWhen Calorie is capitalized, as in a nutritional Calorie, it generally meanskilocalorie on the metric scaledo all of these equal 1 kilocalorie (kcal) = 1000 calories (cal) = 1 Calorie (Cal)yesThe modern systems of units uses the joule (J), as a unit ofenergy equal to 0.239 calIn terms of calorie equivalents, 1 cal = what J4.184 JCarbohydrates (sugars) and fats are categories of biomolecules that provide our bodies withenergyCarbohydrates and fats provide the body energy becausewhen they react with oxygen, their products have less potential energy than the reactantscarbohydrates and fats provide an energy difference that isboth transformed into usable energy in the body and dissipated as heat throughout the bodyA calorimeter is a device used toexperimentally measure the quantity of heat energy released in a combustion reactionThe heat of combustion is the quantity ofheat energy given off when a specified amount of a substance burns in oxygenEnergy is released when the atoms from the reactantschange their interactions and "fall" to a state of lower potential energy as they are transformed into productsExothermic is a term applied to anychemical or physical change accompanied by the release of heatthe negative sign attached to the energy change for all exothermic reactions signifiesthe decrease in potential energy going from reactants to productsIn terms of heat energy released during combustion, the more energy released, the better thefuelGeneralizations based on the chemical formulas of the fuels:1) the fuels with the highest heats of combustion are hydrocarbons 2) as the ratio of hydrogen-to-carbon decreases, the heat of combustion decreases 3) as the amount of oxygen in the fuel molecule increases, the heat of combustion decreasesEndothermic is the term applied to anychemical or physical change that absorbs energy and creates products of a higher potential energy stateThe convention for representing an endothermic reaction is to place apositive sign (or no sign at all) in front of the energy value and unitForming chemical bondsrelease energyForming chemical bonds release energy: The overall energy change associated with a chemical reaction depends on thenet difference of the energy needed to break bonds, and the energy to released when bonds formBond energy is the amount of energy that must beabsorbed to break a specific chemical bondBecause energy must be absorbed, breaking bonds is anendothermic processTo determine whether the overall reaction is endothermic or exothermic, we need to keep track of whether energy isabsorbed or releasedWe indicate when energy is absorbed with a positive sign. This is the energyabsorbed when the bond is brokenForming a bond releases energy, and the sign isnegativeThe energy change that accompanies a chemical reaction is a state function, depending only onthe energy difference between the products and the reactants, not on the particular process, mechanism, or individual steps that connect the twoOne possible source of error is that the bond energies listed in figure 6.2 apply only togasesHence, calculations are most accurate if all reactants and products are in thegaseous stateThe strength of a bond depends on the overallstructure of the molecule in which it is found; in other words, what else the atoms are bonded toThe first step in producing electricity from coal is toburn itIn the coal beds of the boiler, the temperature can reach650 degrees CeleisusThe second step in producing electricity is to usethe heat released from combustion to boil water-usually in a closed, high-pressure systemThe elevated pressure serves two purposes1) it raises the boiling point of water above 100 degrees Celsius 2) it compresses the resulting water vaporElectrical energy which is another form ofkinetic energyA summary of the energy transformation in a fossil fuel-powered electric power plant:potential energy (fuel molecules) -> kinetic energy -> mechanical energy -> electrical energy where all the arrows are: burner - turbine - generatorThe third and final step generateselectricitywhat are the steps that generates electricityAs the steam expands and the cools, it rushes past the turbine, causing it to spin The shaft of the turbine is connected to a large coil of wire that rotates within a magnetic field, and the turning of this coal generates an electric current Meanwhile, the water vapor leaves the turbine and continues to cycle through the system It passes through a condenser, where a stream of cooling water carries away the remainder of the heat energy originally acquired from the fuel The condensed water then re-enters the boiler, ready to resume the energy trainer cycleIn the early 1800s, ___ was the major energy source in the United StateswoodBy the 1960s, most coal was used for generatingelectricityAn approximate chemical formula for coal is C135H96O9NS, which corresponds to a carbon content of about ___ by mass. The other small amounts in coal come from the ___85% ancient plant material and other substances present when the plants were buriedCoal is a better fuel than wood because coal containshigher percentage of carbon and a lower percentage of oxygenwhat are coals serious drawbacks1) the first of which relates to underground mining that is both dangerous and expensive 2) the environmental harm caused by coal mining 3) coal is a dirty fuel 4) burning of coal produces gases that contribute to acid rain, as well as global warming2) the environmental harm caused by coal mining When groundwater infiltrates abandoned mine shafts, or comes in contact with sulfur-rich rock often associated with coal deposits, it becomesacified2) the environmental harm caused by coal mining This acidic mine drainage also dissolves excessive amounts of iron and aluminum, making the wateruninhabitable for many fish species and placing drinking water sources at risk for many communities3) coal is a dirty fuel The issue is the dirtycombustion products4) burning of coal produces gases that contribute to acid rain, as well as global warming ___ has been ranked as the world's fastest-growing fossil fuel sourcecoalA safe mining technique is called themountain miningthe mountain mining process calls forscraping away the overlying vegetation, and then blasting off the top several hundred feet of a mountain to reveal the underlying coal seamMountaintop mining creates massive quantities of ___ that are often disposed of by dumping the debris into nearby river valleysrubbleIncreased sediments and mineral content in the surrounding water systems have adversely affected manyaquatic ecosystemsThe airborne coal-dust particulates generated by this practice have been implicated in a number ofhealth issues such as lung cancer and birth defectsWhen coal is burned, microscopic particulates known as ___ ___ are generated in the exhaust gasfly ashA series of filters and precipitators are now used in most coal-fired power plants tocapture the ash before it rises up the chimneyCoal combustion also results in larger/heavier particles known as ___ ___, which are more easily collected at the power plantbottom ashThe composition of coal ash is similar to the elements found inEarth's crustCoal contains only mirror amounts of mercury, lead, and cadmium; however, these toxic elements may becomeconcentrated in the ash and may leach into the environment from landfills or storage sitesIn order to prevent environmental harm and enhance sustainability, there has been much recent interest inreusing coal ash waste for consumer productsIn order to prevent environmental harm and enhance sustainability, there has been much recent interest in reusing coal ash waste for consumer products such asConcrete, carpet backing, fire and heat protection devices, automobile and mobile bodies, insulation, paints, and even toothpaste"Clean coal" is promoted by its supporters as an importantstep toward decreasing our reliance on petroleum imports and reducing air pollution"Clean coal technology" actually encompasses a variety of methods that aim to increase theefficiency of coal-fired power plants while decreasing harmful emissionsThe Lucas Spindletop gusher resulted when peopledrilled into a hill composed of a giant salt dome in southeast Texas released an eruption of oil to heights greater than 150 feet1950 marked the first year that ___ surpassed coal as the major source in the United StatespetroleumPetroleum has the distinct advantage of being aliquid, making it easily pumped to the surface and transported via pipelines to refineriesPetroleum yields about 40-60% more energy per gram thancoalCrude oil ranges from aclear golden viscous fluid to a black tarry liquidThe distinctive foul odor of crude oil pumped from wells or transported by tankers is mostly due tosulfur-containing compounds