What is Exothermic: Definition and 60 Discussions

In thermodynamics, the term exothermic process (exo- : "outside") describes a process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e.g. a battery), or sound (e.g. explosion heard when burning hydrogen). Its etymology stems from the Greek prefix έξω (exō, which means "outwards") and the Greek word θερμικός (thermikόs, which means "thermal"). The term exothermic was first coined by Marcellin Berthelot.
The opposite of an exothermic process is an endothermic process, one that absorbs energy usually in the form of heat. The concept is frequently applied in the physical sciences to chemical reactions where chemical bond energy is converted to thermal energy (heat).

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  1. Beowulf_8991

    Would this reaction be exothermic or endothermic?

    Summary:: A tertiary allylic alcohol rearranges to become a primary allylic alcohol, would it be exothermic because the final product is more stable and lower in energy? Hi all, this problem's been on my mind for a couple of days now and I'm not making any progress with it. My problem is that...
  2. A

    Non-combustible exothermic oxidation of a Hydrocarbon

    I have 2 queries and would be great if someone can lead me to some specific answers - 1. Is it possible to oxidise a complex hydrocarbon like Ethanol or Gasoline in a non-combustible but exothermic reaction? 2. If this kind of oxidation is possible, what would be the best catalysts to achieve...
  3. J

    Looking for intuition on exothermic reactions

    All, I am looking for a logical step that I must be missing in order to understand how heat energy is produced in an exothermic reaction. All of the standard explanations--more heat is given off than is taken in--don't seem satisfying. If heat is the result of the kinetic energy of molecules...
  4. M

    Exothermic Energy: Explaining Hydration of Sulphuric Acid

    Good Morning, is it possible to get a physical model, I think to electromagnetic fields, to explain the energy developed in exothermic reactions es. for the hydration of sulphuric acid? thank you
  5. P

    Is Ammonia absorption in water exothermic?

    A person working in a company that manufactures absorption refrigerator told me that when Ammonia dissolves in water, the water temperature rises. In short, Ammonia absorption is water is exothermic. If it's true, then what's the reason behind it? Is it due to the fact that the latent heat of...
  6. A

    Quantum mechanics -- explanation of exothermic reactions

    Hi, I am wondering about latent heat release when water freezes but it seems best to start with a regular exothermic reaction. How does bond formation create heat? What is actually happening at the microscopic level so that these combining particles are capable of causing adjacent molecules...
  7. T

    I How endothermic reactions happen?

    Ok, this is a large qiestion. Firstly, from second law of thermodynamics, thermal flow always happens between matters kept in different temparature. But while an endothermic reaction takes place, it may extract some heat from environment and consume it. Isnt it against second law? And for...
  8. E

    Exothermic reaction of zeolite and water

    So, I was reading about zeolites: https://en.wikipedia.org/wiki/Zeolite One of the things it is used for, is in the heating industry, namely: "Zeolites can be used as solar thermal collectors and for adsorption refrigeration. In these applications, their high heat of adsorptionand ability to...
  9. terryds

    Why reaction between alkali metals and water exothermic?

    Why the reaction between alkali metals and water exothermic?? I know that it produces heat to surroundings But, what actually happens?? Why it gives heat to surroundings?? http://antoine.frostburg.edu/chem/senese/101/thermo/faq/exothermic-endothermic-examples.shtml says that when forming ion...
  10. T

    Why is electron gain enthelpy generally exothermic?

    I understand that we need to supply energy to counter the nuclear attraction when we remove electrons and that is the reason ionization energy is endothermic. However, why does an atom release energy when we add an electron to it? And also why do some elements( like the halogens) release more...
  11. F

    Why is combustion exothermic and what role does oxygen's electronegativity play?

    hello! what is the atomic mechanism of combustion that makes it so exothermic? what makes O2 so reactive with hydrocarbons for example and why is the reaction exothermic? thanks
  12. lonely_nucleus

    Direction of equilibrium if you remove heat from exothermic reaction

    If you remove heat from an exothermic reaction will the equilibrium shift to the products or to the reactants according to le chatelier's principle
  13. MexChemE

    Energy balance -- Physical interpretation of Q

    Hello PF! I have a simple question on energy balances. Suppose you have an isothermal reactor where you want to have an exothermic reaction happening at 450 °C. The simplified energy balance for the reactor is Q = ΔH. Supposing ΔH = -150 kcal, then Q = -150 kcal. Does this mean that, a) in order...
  14. MexChemE

    Exothermic reaction in adiabatic reactor

    Homework Statement One mole of gas A, two moles of gas B, and one mole of inert gas I are fed into an adiabatic reactor of variable volume and constant pressure at 25 °C. At this temperature, the reaction yielding liquid R proceeds normally as: \textrm{A} (g) + \textrm{B} (g) \rightarrow...
  15. Q

    Most Exothermic Combustion of Hydrocarbon

    Homework Statement Which would have the most negative heat of combustion? Consider only the best conformer. cis-1,3-dimethylcyclohexane trans-1,4-dimethylcyclohexane Homework Equations The more negative the heat of combustion, the more exothermic the combustion. We are...
  16. Q

    Which of the following reactions is likely more exothermic?

    Homework Statement Which of the following reactions is likely more exothermic? 1) Vaporized sodium metal reacts with diatomic chlorine gas to form one mole of solid sodium chloride. 2) Solid sodium metal reacts with diatomic chlorine gas to form one mole of solid sodium chloride...
  17. Entanglement

    Affect of temperature on exothermic reactions

    Does heat affect the rate of an exothermic reaction?? In my point of view it shouldn't affect it since exothermic reactions are spontaneous so it already works as fast as it can.
  18. M

    Are all exothermic processes exergonic?

    Are all exothermic processes exergonic? What is exactly meant by the term of standard enthalpy of fusion? For example, if you have water that has a melting point at 273.15 K, what exactly is meant/measured by this enthalpy when it is already fully melted at 298.15 K? Just had these...
  19. gauss44

    Can a reaction be exothermic due to increased kinetic energy?

    Homework Statement Examkrackers Lecture question - MCAT Prep book 116. A student holds a beaker of pure liquid A in one hand and pure liquid B in the other. Liquid A has a higher boiling point than liquid B. When the student pours a small amount of liquid B into liquid A, the temperature of...
  20. A

    Striking a match, Endothermic or Exothermic?

    Homework Statement I was wondering whether striking a match is endothermic or exothermic. Homework EquationsThe Attempt at a Solution This seems quite straight forward as striking a match releases heat, which is obviously exothermic. However, the process of igniting the match requires heat...
  21. S

    Why is the mixing of ethanol and water exothermic?

    Why is the mixing of ethanol and water exothermic? Because unless there's a reaction I'm thinking by the law of conservation of energy the total energy of the bonds should remain the same before and after. Because considering hydrogen bonds, the total number of bonds is dependent on the...
  22. S

    Thermodynamics of exothermic reactions in hand warmers

    I was reading online about the reactions used in hand warmers. One website that their version always heats up to 54 C (http://www.heatinaclick.com/Default.asp?sType=0&PageId=81390). This one works by a supersaturated fluid of sodium acetate crystallizing. Other hand warmers work by oxidation...
  23. T

    Determine if chemical equation is exothermic or endothermic?

    How would I determine, if given a chemical equation is exothermic or endothermic? Eg. Mg + 2HCL\rightarrowMgCl2 + H2
  24. F

    Temperature change for an exothermic reaction

    1. Will the recorded temperature change for an exothermic reaction performed in a glass calorimeter be greater or less than that in a styrofoam coffee cup calorimeter? Assume glass to be a better conductor of heat than styrofoam. Please explain
  25. I

    Can someone explain why this dissolution is exothermic rather than endothermic?

    A pair of students found the temperature of 100 g of water to be 27.0°C. They then dissolved 6.32 g of KOH in the water. When the salt had dissolved, the temperature of the water was 42.5°C. If the temperature of the water is raised, doesn't that mean it retained heat, thus showing that the...
  26. J

    Combustion is any exothermic reaction?

    What is combustion - is it any reaction that produces energy? Or is it an exothermic reaction involving oxygen?
  27. B

    Why is the formation of ionic compounds exothermic?

    Hello everyone, I've been trying to figure out why when ionic compounds are formed that they are exothermic (meaning they give off heat). The only theory I have is that when the ions are coming together, the motion from them moving and possibly the friction of their surfaces making contact...
  28. D

    Is this nuclear reaction exothermic or endothermic?

    Is this nuclear reaction exothermic or endothermic?? Homework Statement Is this nuclear reaction exothermic or endothermic?? alpha particle + beryllium -> carbon12 + neutron Homework Equations The Attempt at a Solution Im not quiet sure which one it is, I don't know what...
  29. G

    Is this homework assignment exothermic or endothermic?

    Homework Statement Label each of the following reactions as exothermic or endothermic ("exo" or "endo"), and according to whether work is done on or by the system, or no work is done at all ("on", "by" or "none")? Note that no "endo-on" cases appear here, as these are always thermodynamically...
  30. J

    Is decay of Z or W bosons exothermic?

    Z and W bosons have very short lives. I assume their decay is exothermic? Is this true? I've seen various feynman diagrams showing how these particles decay, but I'm having trouble verifying that their decay is exothermic. Also, does either of their decay emit dangerous radiation, or is it...
  31. M

    Kinetic/Potential Energy Change in an Exothermic Reaction

    I am having trouble understanding what exactly happens in an exothermic reaction. Specifically, I need to answer the following question: In an exothermic reaction: a) the kinetic energy increases and the potential energy decreases. b) the kinetic energy and the potential energy decrease...
  32. S

    Endothermic vs Exothermic Reactions in Ammonia Production

    Homework Statement Is the reaction for the production of ammonia an endothermic reaction or an exothermic reaction? Explain. Homework Equations n/a The Attempt at a Solution I know that the production of ammonia in the Haber process is indeed exothermic and that the backwards reaction (NH3...
  33. H

    Endothermic / exothermic reaction

    Hello, I need a few compounds that i can use that are soluble with water that causes the water to cool, so that if ingested it will not do any harm. your advice would be greatly appreciated, also if you may include a chemical formula if it is known. THANK YOU. P.S. this is out of interest...
  34. S

    Exothermic Reactions: Heat Packs & Sodium Acetate

    Hello, There is something that has been puzzling me. Sorry if I don't use the correct terminology, this is not my field. When a heat pack made of sodium acetate starts its exothermic reaction, does it release heat for only 15 seconds, but feels hot for ~30 minutes because the sodium acetate...
  35. 7

    Exothermic Reaction Materials: 180-190 C, Safe & Easy to Acquire

    Not getting any responses in the Chemical Engineering so I'll try here :) Hi all, I'm looking for two material to produce an exothermic reaction of 180-190 C. I'd prefer the materials to be cheap in larger quantities (think mass production, not mass explosion :smile:). Safe, other than...
  36. 7

    Exothermic chemical reaction materials

    Hi all, I'm looking for two material to produce an exothermic reaction of 180-190 C. I'd prefer the materials to be cheap in larger quantities (think mass production). Safe, other than the heat concerns. Not extremely corrosive, toxic... Easy to clean once combined. Prefer materials that...
  37. E

    Are all neutralization reactions exothermic?

    Homework Statement When acid gets on your skin, why must you flush the area with plenty of water rather than neutralizing with a base? Homework Equations The Attempt at a Solution I'm guessing it's because neutralization reactions are exothermic so heat could be released, thus...
  38. L

    Exothermic reaction moves forward with increase in Temp?

    I did an equilibrium calculation with some chem software that I have and it told me that a syngas reaction CH4+0.5O2\rightarrow 2H_{2}+CO which is an exothermic reaction will proceed to completion at high temperature. If you increase temperature, that should drive the reaction backwards...
  39. D

    Thermodynamics: Exothermic & endothermic reaction in counter current flow

    Hi guys, I have a scenario here; let's say we have a exothermic reaction and a endothermic reaction going in co-current flow reactor (separated by a thin wall to facilitate heat transfer). At steady state after some time, from the concentration profile, we have the endothermic reaction going at...
  40. P

    Are exothermic reactions spontaneous?

    The reaction between 2KOH + H2SO4 -> K2SO4 + 2H2O is exothermic... However is this reaction spontaneous as well? If so then why? the concentration that i used was: KOH - 2M H2SO4 - 1M (I writting a lab report on the "course of this reaction"...spontaniety of the reaction is a...
  41. Char. Limit

    Is Hell exothermic or endothermic?

    Let's assume for the sake of discussion that hell is not "neither".
  42. C

    Generating an Exothermic Reaction with Vinegar and Bicarb

    Ok so I have some vinegar and Bicarb and want to generate an exothermic reaction, but just mixing them produces CO2 in an endothermic reaction! How can I do this? Thank you.
  43. kandelabr

    Reversible exothermic reaction

    hello guys. first, i must say that chemistry never was my beloved subject, that's why I don't know much about it, so please be patient. o.0 well, i need a heat reservoir*. it should have high energy density and should not lose stored energy over time. the heat should be released on demand...
  44. Topher925

    Is the oxidization of a substance ever exothermic?

    Like the question states, if you remove the electrons from an atom using some catalyst, will that reaction be exothermic or neutral. For example oxidization of hydrogen using platinum. H2 + Pt = PtH+2 + 2e- Would this reaction absorb or emit any heat? I wouldn't think so since I think...
  45. I

    Series of physical events in an exothermic reaction

    I am having trouble clearly/completely understanding the main cause of a transfer of thermal energy into the environment as a result of a bond formation. In terms of a very simple, generic, exothermic reaction... What I know...I can picture the atoms coming together through electrical...
  46. I

    Is hell exothermic or endothermic interesting find

    Apparently students were given an assignment to prove whether hell obeyed the laws of thermodynamics and if it was endothermic or exothermic. The most interesting response is given below. http://wfhummel.cnchost.com/hell.html author unkown.
  47. S

    Exothermic Reactions for Project Experiments

    Hii.. Can anyone tel me... some Exothermic Liquid reactions to carry out experiments for my project work...
  48. K

    MgCl2 + NaOH: Endo or Exothermic?

    I have the equation Mg(OH)2 (s) -> Mg2+ (aq) + 2 OH- (aq) I started out with 20 drops of 1.0M MgCl2 in a well & 10 drops of .5M NaOH. Phenolphthalein was also added. When I heated the mixture, it became white, when it cooled it became pink. So, how can I tell if it was endo or exothermic...
  49. L

    Why exactly is this exothermic

    Bah, template doesn't apply to this. In a lab report, we were using Hess's Law to calculate enthalpies using a few reactions we did in class, one of which was magnesium in hydrochloric acid. The question was to explain why the change is exothermic. What exactly is it about displacement...
  50. T

    Exothermic reactions that release hydrogen?

    Hello, I was wondering if there are any exothermic (or otherwise spontaneous) chemical reactions that release hydrogen, in which the reagents and products aren't strongly hazardous? I know of the reaction of alkali metals with water, but these produce strong alkaline solutions.. Perhaps one...