In chemistry, an exothermic reaction is one that releases heat. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature It is the opposite of an endothermic reaction. In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat. Expressed in a chemical equation:
- reactants → product + energy
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Overview
In an exothermic reaction, the total energy absorbed in bond breaking is less than the total energy released in bond making. A chemical equation is a symbolic representation of a Chemical reaction. In other words, the energy needed for the reaction to occur is less than the total energy provided. As a result of this, the extra energy is released, usually in the form of heat.
When using a calorimeter, the change in heat of the calorimeter is equal to the opposite of the change in heat of the system. A calorimeter is a device used for Calorimetry, the Science of measuring the heat of Chemical reactions or Physical changes as well as Heat This means that when the medium in which the reaction is taking place gains heat, the reaction is exothermic.
The absolute amount of energy in a chemical system is extremely difficult to measure or calculate. The enthalpy change, ΔH, of a chemical reaction is much easier to measure and calculate. In Thermodynamics and molecular chemistry, the enthalpy (denoted as H, h, or rarely as χ) is a quotient or description of A bomb calorimeter is very suitable for measuring the energy change, ΔH, of a combustion reaction. A calorimeter is a device used for Calorimetry, the Science of measuring the heat of Chemical reactions or Physical changes as well as Heat Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of Measured and calculated ΔH values are related to bond energies by:
- ΔH = energy used in bond breaking reactions - energy released in bond making products
by definition the enthalpy change has a negative value:
- ΔH < 0
For an exothermic reaction, this gives a negative value for ΔH, since a larger value (the energy released in the reaction) is subtracted from a smaller value (the energy used for the reaction). For example, when hydrogen burns:
- 2H2 + O2 → 2H2O
- ΔH = -483. 6 kJ/mol of O2
Examples of exothermic reactions
- Combustion reactions of fuels
- Neutralization reactions such as direct reaction of acid and base
- Adding concentrated acid to water
- Adding water to anhydrous copper(II) sulfate
- The Thermite reaction
- Reactions taking place in a self-heating can based on lime and aluminium
- The setting of cement and concrete
- Many corrosion reactions such as oxidation of metals
- Most polymerisation reactions
- The Haber-Bosch Process of ammonia production
Key points
- The concept and its opposite number endothermic relate to the enthalpy change in any process not just chemical reaction. Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of Fuel is any material that is burned or altered in order to obtain energy As a general term a substance is said to be anhydrous if it contains no Water. Copper(II sulfate is the Chemical compound with the formula Cu[[Sulfur S]] O 4 Thermite is a Pyrotechnic composition of Aluminium powder and a metal oxide which produces an Aluminothermic reaction known as a A self-heating can is an enhancement of the common food can. Self-heating cans have dual chambers one surrounding the other Lime is a general term for various naturally occurring Minerals and materials derived from them in which Carbonates Oxides and Hydroxides of WikipediaNaming In the most general sense of the word a cement is a binder a substance which sets and hardens independently and can bind other materials together Concrete is a construction material composed of Cement (commonly Portland cement) as well as other cementitious materials such as Fly ash and Slag Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state In Polymer chemistry, polymerization is a process of reacting Monomer Molecules together in a Chemical reaction to form three-dimensional networks Because of its many uses Ammonia is one of the most highly-produced inorganic chemicals In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat.
- In endergonic reactions and exergonic reactions it is the sign of the Gibbs free energy that count and not enthalpy. In chemical thermodynamics, an endergonic reaction (also called an unfavorable reaction or a nonspontaneous reaction) is a chemical reaction in which the An exergonic reaction is a chemical reaction that involves a net release of free energy is a Chemical reaction where the variation of Gibbs free energy is negative In Thermodynamics, the Gibbs free energy ( IUPAC recommended name Gibbs energy or Gibbs function) is a Thermodynamic potential which In Thermodynamics and molecular chemistry, the enthalpy (denoted as H, h, or rarely as χ) is a quotient or description of the related concepts endergonic and exergonic apply to all physical processes. Endergonic means absorbing energy in the form of work Its etymology stems from the suffix -ergonic as derived from the Greek root ergon meaning work, Exergonic means to release energy in the form of work Its etymology stems from the suffix -ergonic, as derived from the Greek root ergon meaning work,
- the conceptually related endotherm and exotherm are concepts in Animal physiology. In Biology, a warm-blooded Animal species is one whose members maintain thermal Homeostasis; that is they keep their body temperature at a roughly constant In Biology, a warm-blooded Animal species is one whose members maintain thermal Homeostasis; that is they keep their body temperature at a roughly constant
- In quantum numbers, when any exited energy level goes down to its original level for example: when n=4 fall to n=2, energy is released so, it is exothermic.
Measurement
Heat production or absorption in either a physical process or chemical reaction are measured using calorimetry. Calorimetry is the Science of measuring the Heat of Chemical One common laboratory instrument is the Differential scanning calorimeter or DSC, where a small sample is slowly heated in a controlled way and the heat flow into or from the sample chamber is monitored. Differential scanning calorimetry or DSC is a thermoanalytical technique in which the difference in the amount of Heat required to increase the Temperature The technique can be used to follow chemical reactions as well as physical processes, such as melting and boiling (both of which are endothermic). In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat. Crystallization and condensation, the reverse processes, are both exothermic.
See also
- Chemical thermodynamics
- Differential scanning calorimetry
- Endergonic
- Exergonic
- Endergonic reaction
- Exergonic reaction
- Exothermic
- Endothermic reaction
- Endotherm
- Exotherm
External links
In Thermodynamics, chemical thermodynamics is the mathematical study of the interrelation of Heat and work with Chemical reactions or with a Differential scanning calorimetry or DSC is a thermoanalytical technique in which the difference in the amount of Heat required to increase the Temperature Endergonic means absorbing energy in the form of work Its etymology stems from the suffix -ergonic as derived from the Greek root ergon meaning work, Exergonic means to release energy in the form of work Its etymology stems from the suffix -ergonic, as derived from the Greek root ergon meaning work, In chemical thermodynamics, an endergonic reaction (also called an unfavorable reaction or a nonspontaneous reaction) is a chemical reaction in which the An exergonic reaction is a chemical reaction that involves a net release of free energy is a Chemical reaction where the variation of Gibbs free energy is negative In Thermodynamics, the word exothermic "outside heating" describes a process or reaction that releases Energy usually in the form of Heat, but In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat. In Biology, a warm-blooded Animal species is one whose members maintain thermal Homeostasis; that is they keep their body temperature at a roughly constant In Biology, a warm-blooded Animal species is one whose members maintain thermal Homeostasis; that is they keep their body temperature at a roughly constantDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic