has_part heptane
___MASK76___ - Heptane is the straight - chain alkane with the chemical formula H3C ( CH2 ) 5CH3 or C7H16 . When used as a test fuel component in anti - knock test engines , a 100 % heptane fuel is the zero ___MASK48___ of the octane rating scale ( the 100 ___MASK48___ is a 100 % iso - octane ) . Octane number equates to the anti - knock qualities of a comparison mixture of heptane and isooctane which is expressed as the percentage of isooctane in heptane and is listed on pumps for gasoline dispensed in the United States and internationally . An ___MASK27___ or motor is ___MASK49___ machine designed to convert ___MASK72___ form of energy into mechanical energy . Heat engines burn ___MASK49___ fuel to create heat , which then creates ___MASK49___ force . Electric motors convert electrical energy into mechanical motion ; pneumatic motors use compressed air and clockwork motors in wind - up toys use elastic energy . In biological systems , molecular motors , like myosins in muscles , use chemical energy to create forces and eventually motion . The diesel ___MASK27___ ( correctly known as ___MASK49___ compression - ignition or CI ___MASK27___ ) is an internal combustion ___MASK27___ in which ignition of the fuel that has been injected into the combustion ___MASK98___ is caused by the high ___MASK10___ which ___MASK49___ ___MASK40___ achieves ( i . ___MASK78___ . the ___MASK31___ ) when greatly compressed ( adiabatic compression ). Diesel engines work by compressing only the ___MASK31___ . This increases the ___MASK31___ ___MASK10___ inside the cylinder to such ___MASK49___ high degree that it ignites atomised diesel fuel that is injected into the combustion ___MASK98___ . This contrasts with spark - ignition engines such as ___MASK49___ petrol ___MASK27___ ( gasoline ___MASK27___ ) or ___MASK40___ ___MASK27___ ( using ___MASK49___ gaseous fuel as opposed to petrol ), which use ___MASK49___ spark plug to ignite an ___MASK31___ - fuel mixture . In compression - ignition engines , glow plugs ( combustion ___MASK98___ pre - warmers ) may be used to aid starting in cold weather , or when the ___MASK27___ uses ___MASK49___ lower compression - ratio , or both . The original compression - ignition ___MASK27___ operates on the " constant pressure " cycle of gradual combustion and produces no audible knock . ___MASK25___ is ___MASK49___ chemical ___MASK52___ with chemical symbol ___MASK14___ and atomic number 1 . With an atomic weight of , hydrogen is the lightest ___MASK52___ on the periodic table . Its monatomic form ( ___MASK14___ ) is the most abundant chemical substance in the Universe , constituting roughly 75 % of all baryonic mass . Non - remnant stars are mainly composed of hydrogen in the plasma state . The most common isotope of hydrogen , termed " protium " ( name rarely used , symbol ___MASK14___ ), has one ___MASK92___ and no neutrons . Fractional distillation is the separation of ___MASK49___ mixture into its component parts , or fractions , separating chemical compounds by their boiling ___MASK48___ by heating them to ___MASK49___ temperature at which ___MASK72___ or more fractions of the compound will vaporize . It uses distillation to fractionate . Generally the component parts have boiling points that differ by less than 25 ° ___MASK9___ from each other under ___MASK49___ pressure of ___MASK72___ atmosphere . If the difference in boiling points is greater than 25 ° ___MASK9___ , ___MASK49___ simple distillation is typically used . The static compression ratio of an internal - combustion ___MASK27___ or external combustion ___MASK27___ is ___MASK49___ value that represents the ratio of the volume of its combustion ___MASK98___ from its largest capacity to its smallest capacity . It is ___MASK49___ fundamental specification for many common combustion engines . Cetane number , Cetane rating or CN is an indicator of the combustion ___MASK87___ of diesel fuel and compression needed for ignition . It is an inverse of the similar octane rating for gasoline . The CN is an important factor in determining the quality of diesel fuel , but not the only ___MASK72___ ; other measurements of diesel ' s quality include ( but are not limited to ) energy content , density , lubricity , cold - flow properties and sulphur content . Petroleum ( from : " rock " + " oleum ": " ___MASK70___ ". ) is ___MASK49___ naturally occurring , yellow - to - ___MASK54___ ___MASK28___ found in geological formations beneath the Earth ' s surface , which is commonly refined into various types of fuels . Components of petroleum are separated using ___MASK49___ technique called fractional distillation . An ion is an ___MASK33___ or a molecule in which the total number of electrons is not equal to the total number of protons , giving the ___MASK33___ or molecule a net positive or negative electrical charge . Ions can be created , by either chemical or physical means , via ionization . The structural formula of ___MASK49___ ___MASK42___ is ___MASK49___ graphic representation of the molecular structure , showing how the atoms are arranged . The chemical bonding within the molecule is also shown , either explicitly or implicitly . Unlike chemical formulas , which have ___MASK49___ limited number of symbols and are capable of only limited descriptive power , structural formulas provide ___MASK49___ complete geometric representation of the molecular structure . For example , many chemical compounds exist in different isomeric forms , which have different enantiomeric structures but the same chemical formula . A structural formula is able to indicate arrangements of atoms in three dimensional ___MASK50___ in ___MASK49___ way that ___MASK49___ chemical formula may not be able to do . Organic ___MASK100___ is a ___MASK100___ subdiscipline involving the scientific study of the structure , properties , and reactions of organic compounds and organic materials , i . e ., matter in its various forms that contain ___MASK12___ atoms . Study of structure includes many physical and chemical methods to determine the chemical composition and the chemical constitution of organic compounds and materials . Study of properties includes both physical properties and chemical properties , and uses similar methods as well as methods to evaluate chemical reactivity , with the aim to understand the behavior of the organic matter in its pure form ( when possible ), but also in solutions , mixtures , and fabricated forms . The study of organic reactions includes probing their scope through use in preparation of target compounds ( e . g ., natural products , drugs , polymers , etc .) by chemical synthesis , as well as the focused study of the reactivities of individual organic molecules , both in the laboratory and via theoretical ( in silico ) study . ___MASK49___ fuel is any material that can be made to react with other substances so that it releases chemical or nuclear energy as heat or to be used for ___MASK74___ . The concept was originally applied solely to those materials capable of releasing chemical energy but has since also been applied to other sources of heat energy such as nuclear energy ( via nuclear fission and nuclear fusion ). An ___MASK33___ is the smallest constituent unit of ordinary matter that has the properties of a chemical ___MASK52___ . Every ___MASK79___ , liquid , gas , and plasma is composed of neutral or ionized atoms . Atoms are very small ; typical sizes are around 100 picometers ( a ten - billionth of a meter , in the short scale ). Ethane ( or ) is an organic ___MASK42___ with chemical formula CH . At standard temperature and pressure , ethane is a colorless , odorless ___MASK40___ . Like many hydrocarbons , ethane is isolated on an industrial scale from natural ___MASK40___ and as a petrochemical byproduct of petroleum refining . Its chief use is as feedstock for ethylene production . Combustion or burning is ___MASK49___ high - ___MASK10___ exothermic redox chemical reaction between ___MASK49___ fuel ( the reductant ) and an oxidant , usually atmospheric ___MASK41___ , that produces oxidized , often gaseous products , in ___MASK49___ mixture termed as smoke . Combustion in ___MASK49___ ___MASK89___ produces ___MASK49___ flame , and the heat produced can make combustion self - sustaining . Combustion is often ___MASK49___ complicated sequence of elementary radical reactions . ___MASK79___ fuels , such as wood , first undergo endothermic pyrolysis to produce gaseous fuels whose combustion then supplies the heat required to produce more of them . Combustion is often hot enough that light in the form of either glowing or ___MASK49___ flame is produced . A simple example can be seen in the combustion of hydrogen and ___MASK41___ into water vapor , ___MASK49___ reaction commonly used to fuel rocket engines . This reaction releases 242 kJ / mol of heat and reduces the enthalpy accordingly ( at constant ___MASK10___ and pressure ): ___MASK49___ molecule is an electrically neutral group of two or more atoms held together by chemical bonds . Molecules are distinguished from ions by their lack of electrical charge . However , in quantum physics , organic ___MASK100___ , and biochemistry , the term " molecule " is often used less strictly , also being applied to polyatomic ions . An organic compound is virtually any ___MASK42___ that contains ___MASK12___ , although a consensus definition remains elusive and likely arbitrary . Organic compounds are rare terrestrially , but of central importance because all known life is based on organic compounds . The most basic petrochemicals are considered the building blocks of organic chemistry . Octane is ___MASK49___ hydrocarbon and an alkane with the chemical formula CH , and the condensed structural formula CH ( CH ) CH . Octane has many structural isomers that differ by the amount and location of branching in the ___MASK12___ chain . One of these isomers , 2 , 2 , 4 - trimethylpentane ( isooctane ) is used as one of the standard values in the octane rating scale . The connectivity of ___MASK49___ molecule often has ___MASK49___ strong influence on its physical and chemical properties and ___MASK71___ . Two molecules composed of the same numbers of the same types of atoms ( i . e . ___MASK49___ pair of isomers ) might have completely different chemical and / or physical properties if the atoms are connected differently or in different positions . In such cases , ___MASK49___ structural formula is useful , as it illustrates which atoms are bonded to which other ones . From the connectivity , it is often possible to deduce the approximate shape of the molecule . ___MASK46___ is ___MASK49___ continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere . It can also be considered ___MASK49___ northern subcontinent of the Americas . It is bordered to the north by the ___MASK88___ , to the east by the ___MASK51___ , to the west and south by the Pacific Ocean , and to the southeast by ___MASK29___ and the Caribbean Sea . An octane rating , or octane number , is ___MASK49___ standard measure of the performance of an engine or aviation fuel . The higher the octane number , the more compression the fuel can withstand before detonating ( igniting ). In broad terms , fuels with ___MASK49___ higher octane rating are used in high performance gasoline engines that require higher compression ratios . In contrast , fuels with lower octane numbers ( but higher cetane numbers ) are ideal for diesel engines , because diesel engines ( also referred to as compression - ignition engines ) do not compress the fuel , but rather compress only ___MASK31___ and then inject fuel into the ___MASK31___ which was heated by compression . Gasoline engines rely on ignition of ___MASK31___ and fuel compressed together as ___MASK49___ mixture , which is ignited at the end of the compression stroke using spark plugs . Therefore , high compressibility of the fuel matters mainly for gasoline engines . Use of gasoline with lower octane numbers may lead to the problem of engine knocking . Distillation is ___MASK49___ process of separating the component or substances from ___MASK49___ ___MASK28___ mixture by selective evaporation and condensation . Distillation may result in essentially complete separation ( nearly pure components ), or it may be ___MASK49___ partial separation that increases the concentration of selected components of the mixture . In either case the process exploits differences in the volatility of the mixture ' s components . In industrial chemistry , distillation is ___MASK49___ unit operation of practically universal importance , but it is ___MASK49___ physical separation process and not ___MASK49___ chemical reaction . ___MASK12___ ( from " coal ") is a chemical element with symbol ___MASK9___ and atomic number 6 . It is nonmetallic and tetravalent  making four electrons available to form covalent chemical bonds . Three isotopes occur naturally , ___MASK9___ and ___MASK9___ being stable , while ___MASK9___ is a radioactive isotope , decaying with a half - life of about 5 , 730 years . ___MASK12___ is one of the few elements known since antiquity . Methane ( or ) is ___MASK49___ ___MASK42___ with the chemical formula ( ___MASK72___ atom of ___MASK12___ and four atoms of hydrogen ). It is ___MASK49___ group 14 hydride and the simplest alkane , and is the main constituent of natural gas . The relative abundance of methane on Earth makes it an attractive fuel , though capturing and storing it poses challenges due to its gaseous state under normal conditions for temperature and pressure . Gasoline , known as petrol outside ___MASK46___ , is ___MASK49___ transparent , petroleum - derived ___MASK28___ that is used primarily as ___MASK49___ fuel in internal combustion engines . It consists mostly of organic compounds obtained by the fractional distillation of petroleum , enhanced with ___MASK49___ variety of additives . In organic ___MASK100___ , an alkane , or paraffin ( a historical name that also has other meanings ), is an acyclic saturated hydrocarbon . In other words , an alkane consists of hydrogen and ___MASK12___ atoms arranged in a tree structure in which all the ___MASK12___ - ___MASK12___ bonds are single . Alkanes have the general chemical formula . The alkanes range in complexity from the simplest case of methane , CH where " n " = 1 ( sometimes called the parent molecule ), to arbitrarily large molecules . In organic ___MASK100___ , a hydrocarbon is an organic compound consisting entirely of hydrogen and ___MASK12___ , and thus are group 14 hydrides . Hydrocarbons from which one hydrogen atom has been removed are functional groups , called hydrocarbyls . Aromatic hydrocarbons ( arenes ), alkanes , alkenes , cycloalkanes and alkyne - based compounds are different types of hydrocarbons . Structural isomerism , or constitutional isomerism ( per IUPAC ), is ___MASK49___ form of isomerism in which molecules with the same molecular formula have bonded together in different orders , as opposed to stereoisomerism . There are multiple synonyms for constitutional isomers . ___MASK49___ spark plug ( sometimes , in British ___MASK86___ , a sparking plug , and , colloquially , a plug ) is a device for delivering electric current from an ignition ___MASK64___ to the combustion chamber of a spark - ignition engine to ignite the compressed fuel / air mixture by an electric spark , while containing combustion pressure within the engine . ___MASK49___ spark plug has a metal threaded shell , electrically isolated from a central electrode by a porcelain insulator . The central electrode , which may contain a resistor , is connected by a heavily insulated wire to the output terminal of an ignition coil or magneto . The spark plug ' s metal shell is screwed into the engine ' s cylinder ___MASK16___ and thus electrically grounded . The central electrode protrudes through the porcelain insulator into the combustion chamber , forming ___MASK72___ or more spark gaps between the inner end of the central electrode and usually ___MASK72___ or more protuberances or structures attached to the inner end of the threaded shell and designated the " side ", " earth ", or " ground " electrode ( s ). An isomer ( from Greek  , isomerès ; isos = " equal ", méros = " ___MASK36___ ") is a molecule with the same molecular formula as another molecule , but with a different chemical structure . That is , isomers contain the same number of atoms of each ___MASK52___ , but have different arrangements of their atoms . Isomers do not necessarily share similar properties , unless they also have the same functional groups . There are two main forms of isomerism ( or ): structural isomerism ( or constitutional isomerism ) and stereoisomerism ( or spatial isomerism ). Knocking ( also knock , detonation , spark knock , pinging or pinking ) in spark - ignition internal combustion engines occurs when combustion of the ___MASK31___ / fuel mixture in the cylinder does not start off correctly in response to ignition by the spark plug , but ___MASK72___ or more pockets of ___MASK31___ / fuel mixture explode outside the envelope of the normal combustion front .