Chemical energy is a kind of hidden energy, which cannot be directly usedWork, only whenChemical changeIt can only be released into heat energy or other forms of energy.Like oil andcoalOfburningThe energy released by explosive explosion and the chemical change of food in the body belongs to the transformation of chemical energy.Chemical energy refers to the energy stored in the substance according toconservation of energyThis change of energy is the same size as the change of heat energy in the reaction, and the symbol is opposite. When the atoms in the compound participating in the reaction rearrange to produce new compounds, it will lead to the change of chemical energyexothermicorendothermiceffect.
All chemical reactions are essentiallyatomThe change of the movement state of the outermost electron;The energy absorbed or released in chemical reaction is called chemical energy. The source of chemical energy is the result of the change of the outermost electronic motion state of atoms and the change of atomic energy level in chemical reaction.
Atoms are composed ofNucleusAnd electronic backrestelectromagnetic fieldMolecules are made of atoms by electromagnetic field（Chemical bondObjects (solid liquid gas, abiotic and biotic) are bonded by molecules by electromagnetic field (intermolecular force).Chemical bond is an existing form of substance, and chemical bond substance is electromagnetic field substance.Chemical reaction is the process of atoms recombining into new substances.stayChemical reaction processMedium, chemically bondedBond energyenergy levelChange occurs, and then chemical energy phenomenon occurs.When the bond energy (electromagnetic field energy level) increases, it is an energy absorption reaction, and when the bond energy decreases, it is an energy releasing reaction.
Chemical bondThe fracture and formation ofChemical changeThe main reason for energy change in.So, the physicalchemical reactionIt occurs simultaneously with the energy change of the system.
Main role
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All kinds of substances store chemical energy.Different substances not only have different compositions and structures, but also contain different chemical energies.staychemical reactionMedium, in existing chemicalsChemical bondAnd the formation of chemical bonds in the products. Therefore, whether the result of a certain chemical reaction is to absorb or release energy depends on the relative size of the total energy of reactants to the total energy of products.[1]
energy conversion
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Heat conversion
Chemical reaction follows before and after reactionLaw of conservation of mass；Similarly, one kind of energy can be transformed into another, and energy is also conserved, which is“conservation of energy”
practical application
Humans not only use the principle of converting chemical energy into heat energy to obtain the required heat for life, production and scientific research, such as the combustion of fossil fuels, explosive mountain blasting, rocket launching, etc.Chemists also often use heat energy to make many chemical reactions happen, so as to explore the composition, properties or preparation of materials needed, such as high-temperature smelting of metals, decomposition of compounds, etc.
significance
Chemical reaction is accompanied by energy change, which is a major feature of chemical reaction.Chemical energy in chemical substances is converted into heat energy through chemical reaction, which is the source of power for human survival and development;The conversion of heat energy into chemical energy is an indispensable condition and way for people to conduct chemical scientific research and create new substances.[2]
Bioenergy conversion
"Breathing" refers to the inhalation and exhalation of oxygen by organismscarbon dioxide"Cell respiration" refers to the process of oxidizing and decomposing organic matter in cells to release energy.
Respiratory type
Aerobic respiration: (under the action of enzymes)
CsixHtwelveOsix+6H2O+6Otwo→6COtwo+ 12HtwoO+energy
1 mol glucose releases 2870 KJ, 1161 KJ is transferred to ATP (synthesis of 38 mol ATP), the energy efficiency is up to 40%, and the rest is mainly lost in the form of heat energy (1709 KJ).
Anaerobic respiration: (under the action of enzymes)
CsixHtwelveOsix→2CtwoHfiveOH + 2COtwo+Energy
CsixHtwelveOsix→2CthreeHsixOthree+Energy
1mol glucose is decomposed into lactic acid to release 196.65KJ energy, 61.08KJ is transferred to ATP (synthesis of 2mol ATP), and the rest is lost in the form of heat energy.
significance
1. ATP provides energy required for life activities
2. Heat energy keeps body temperature constant[3]
Transfer electric energy
The way of converting chemical energy into electric energy:
Primary battery directly converts chemical energy into electric energy Advantages: clean and efficient
Battery principle
1. Concept: The device that directly converts chemical energy into electrical energy is called primary battery.
2. Operating principle of primary battery: throughRedox reaction(transfer of electrons) converting chemical energy into electrical energy.
3. The conditions for forming the primary battery are: (1) the electrodes are conductors with different activity;(2) Contact between two electrodes (wire connection or direct contact);(3) Insertion of two connected electrodeselectrolyte solutionForm a closed loop.
4. Electrode name and reaction:
negative pole:
The more active metal is used as the negative electrode, and the negative electrode will undergo oxidation reaction,
Negative pole phenomenon: the negative pole dissolves and the negative pole quality decreases.
positive electrode：
The less active metal or graphite is used as the positive electrode, and the positive electrode undergoes a reduction reaction,
Electrode reaction formula: cation+ne -=single substance in solution
Phenomenon of positive pole: gas is generally emitted or the positive pole mass is increased.
Main types
1. Dry battery: active metal is used as negative electrode, which is corroded or consumed.For example: Cu Zn primary battery, zinc manganese battery.
2. Rechargeable battery: the primary battery with both poles participating in the reaction, which can be recharged and recycled.Such as lead batteries, lithium batteries and silver zinc batteries.
3. Fuel cell: both electrode materials are inert electrodes, and the electrodes themselves do not react, but react with substances introduced to the two electrodes, such as Htwo、CHfourThe electrolyte solution of fuel cell is usually alkaline reagent (KOH, etc.).[4]
