Bonding potential energy stored

Likewise, in chemical change, energy is neither created nor destroyed (Law of Conservation of Energy). When charcoal is burned the potential energy stored in the carbon-carbon bonds is released as heat. Although in this reaction the forms of matter and... 

Let s look more closely at spontaneous processes and at the thermodynamic driving forces that cause them to occur. We saw in Chapter 8 that most spontaneous chemical reactions are accompanied by the conversion of potential energy to heat. For example, when methane burns in air, the potential energy stored in the chemical bonds of CH4 and 02 is partly converted to heat, which flows from the system (reactants plus products) to the surroundings ... 

The mathematical model of the batch reactor consists of the equations of conservation for mass and energy. An independent mass balance can be written for each chemical component of the reacting mixture, whereas, when the potential energy stored in chemical bonds is transformed into sensible heat, very large thermal effects may be produced. 

This reaction produces a quantity of energy that is released as heat. This energy flow results from a lowering of the potential energy stored in the bonds of CH4 and 02 as they react to form C02 and H20 (see Fig. 10.1). Potential energy is converted to thermal energy, but the energy content of the universe remains constant. 

The energy diagram for the combustion of methane is shown in Fig. 9.2, where A(PE) represents the change in potential energy stored in the bonds of the products as compared with the bonds of the reactants. In other words. 

Chemical energy (9.2) Potential energy stored in chemical bonds, which can be released through an exothermic reaction. 

Where is this potential energy stored at the transition state It is placed in the form of a torsional strain. As the hydrogens become eclipsed, a distortion of the C-H and C-C bonds occurs (albeit small). As these bonds go back to their normal lengths and angles in the staggered form, the energy required for the distortions is released to the ensemble of molecules or into another vibrational mode of the same molecule. 

An endothermic reaction feels cold to the touch because the reaction (acting here as the system) absorbs heat from the smroundings. When you touch the vessel in which the reaction occius, you, being part of the surroundings, lose heat to the system (the reaction), which makes you feel cold. The heat absorbed by the reaction (from your body, in this case) does not increase its temperature, but rather becomes potential energy stored in chemical bonds. 

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