what bonds are broken during the combustion of methane (ch4) to form water and carbon dioxide?
When does the breaking of chemical bonds release energy?
Category: Chemistry Published: June 27, 2013
The breaking of chemic bonds never releases energy to the external environment. Free energy is merely released when chemical bonds are formed. In general, a chemical reaction involves two steps: 1) the original chemical bonds betwixt the atoms are broken, and 2) new bonds are formed. These 2 steps are sometimes lumped into one consequence for simplicity, but they are really ii divide events. For instance, when you burn marsh gas (natural gas) in your stove, the methane is reacting with oxygen to form carbon dioxide and h2o. Chemists often write this as:
CH4 + 2 O2 → CO2 + two H2O + energy
This balanced chemical equation summarizes the chemical reaction involved in burning methane. The reactants are on the left, the products are on the right, and the arrow represents the moment the reaction happens. But there are a lot of interesting things happening that are hidden behind that arrow. A more than detailed equation would look something similar this:
CHfour + 2 O2 + a trivial energy → C + four H + four O → COii + 2 H2O + lots of energy
The first line of the equation contains the original reactants: methane molecules and oxygen molecules. The outset arrow represents the breaking of the bonds, which requires energy. On the middle line are the atoms, at present cleaved out of molecules and costless to react. The second arrow represents the forming of new bonds. On the last line are the terminal products. Information technology takes a trivial energy, such equally the spark from the igniter in your stove, to get the reaction started. That is because bonds must be broken earlier the atoms can exist formed into new bonds, and it always takes energy to interruption bonds. One time the reaction has started, the output energy from one burned methyl hydride molecule becomes the input energy for the side by side molecule. Some of the energy released past each bond that is formed in making carbon dioxide and h2o is used to break more bonds in the methane and oxygen molecules. In this mode, the reaction becomes cocky-sustaining (as long every bit methane and oxygen continue to exist supplied). The igniter tin be turned off. If breaking bonds did not crave energy, so fuels would not need an ignition device to beginning called-for. They would just start burning on their own. The presence of spark plugs in your automobile attests to the fact that breaking chemical bonds requires energy. (Annotation that the combustion of methane actually involves many smaller steps, so the equation higher up could be expanded out into fifty-fifty more detail.)
The textbook Advanced Biology by Michael Roberts, Michael Jonathan Reiss, and Grace Monger states:
Biologists often talk virtually energy being made available by the breakup of sugar, implying that the breaking of chemical bonds in the sugar molecules releases free energy. And yet in chemistry we learn that energy is released, non when chemical bonds are cleaved, but when they are formed. In fact, respiration supplies free energy, non by the breaking of bonds in the substrate, simply by the formation of strong bonds in the products. However, the overall outcome of the process is to yield free energy, and information technology is in this sense that biologists talk almost the breakup of carbohydrate giving energy.
Burning propane requires an igniter to get the reaction started because chemic bonds must be broken before new ones tin can be formed, and breaking bonds ever requires energy. Public Domain Prototype, source: Christopher S. Baird.
The total energy input or output of a reaction equals the energy released in forming new bonds minus the free energy used in breaking the original bonds. If it takes more energy to pause the original bonds than is released when the new bonds are formed, then the net energy of the reaction is negative. This means that energy must be pumped into the organisation to go on the reaction going. Such reactions are known as endothermic. If if takes less energy to interruption the original bonds than is released when new bonds are formed, and then the internet energy of the reaction is positive. This fact means that the energy will flow out of the system as the reaction proceeds. This fact likewise means that the reaction can go on on its own without any external energy once started. Such reactions are known as exothermic. (Endothermic reactions can also continue on their own if in that location is enough external energy in the course of ambience heat to be absorbed.) Exothermic reactions tend to heat up the surrounding environment while endothermic reactions tend to cool it down. The burning of fuels is exothermic because there is a net release of energy. Cooking an egg is endothermic considering at that place is a cyberspace intake of energy to make the egg cooked. The bottom line is that both endothermic and exothermic reactions involve the breaking of bonds, and both therefore crave free energy to become started.
It makes sense that breaking bonds always takes energy. A chemic bond holds ii atoms together. To break the bond, you have to fight against the bail, like stretching a rubber ring until it snaps. Doing this takes energy. Equally an analogy, call up of atoms as basketballs. Recollect of the energy mural of chemical bonds equally a hilly terrain that the basketballs are rolling over. When 2 balls are placed near a round hole, gravity pulls them downwards to the bottom where they come across and end. The 2 assurance now stay close together because of the shape of the hole and the pull of gravity. This is similar the chemic bond uniting atoms. To become the balls away from each other (to break the bonds), you have to ringlet them upwards opposite sides of the hole. It takes the energy of your hand pushing the balls to become them upwardly the sides of the hole and away from each other. The free energy yous put into the system in order to pull apart the balls is at present stored as potential free energy in the balls. Atoms don't literally coil up and down hills, just they act like they are moving in an energy landscape that is very similar to real hills.
Source: https://www.wtamu.edu/~cbaird/sq/2013/06/27/when-does-the-breaking-of-chemical-bonds-release-energy/
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