<p>Okay this has confused me for centuries.
Now I know Exothermic = Release heat. Gets warm.
Endothermic = Absorb heat. Gets cold.</p>
<p>My question is, if a substance releases heat (i.e. goes through an exothermic reaction), wouldn't it LOSE heat, and therefore become cold?
Similarly, if a substance absorbs heat (i.e. goes through an endothermic reaction), wouldn't it GAIN heat, and therefore become hot?</p>
<p>My teacher told me it doesn't have to do with the temperature of the substance itself, but the temperature of the surroundings/atmosphere around that substance.
Is this true?</p>
<p>Yes. If the surrounding is hotter than the object, then the object is undergoing an endothermic reaction. On the other hand, if the surrounding is colder, the object is undergoing an exothermic reaction.</p>
<p>You're teacher said the same thing mine did. The actual substance itself doesn't matter.</p>
<p>Exothermic reactions release their energy (heat) which is the reason why they make the surroundings feel warm. That's the reason why they feel warm, the energy that escaped during the reaction affects the surroundings.</p>
<p>Endothermic reactions absorb surrounding heat during the reaction, and the surroundings feel cooler because there is less energy in the form of heat surrounding.</p>
<p>I don't know if I helped you at all, because I think I just repeated what your teacher said...xD</p>
<p>And anhtimmy.
The second one makes a lot of sense. :)</p>
<p>You were wrong on the first one because you said when the surroundings are hotter than the object it's ENDOthermic (it should be exo) ... and vice versa.</p>
<p>Any system tends toward thermal equilibrium, meaning, all objects will have same temperature. That means what is hotter will lose heat, or transfer it to colder objects, HEATING up the colder objects so they reach same temperature.</p>
<p>Anhtimmy explanation looks right.</p>
<p>exothermic, means the heat content of the system/reactants decreases (loss of energy) therefore negative delta H. Where did the lost energy go=> as released heat to the surrounding. Energy is conserved.</p>
<p>
[quote]
No, when the surroundings are hotter, the object is RELEASING heat!!!!!
[/quote]
</p>
<p>If the surrounding is hotter, the object is colder. To achieve equilbrium, the object would need to GAIN heat, meaning its ENDOTHERMIC!! >:O</p>
<p>I think you are referring to the surroundings getting hotter. Then I would agree its exothermic. But as you can see, my explanation states that the surroundings are hotter. Not getting hotter. :P</p>
<p>
[quote]
Yes. If the surrounding is hotter than the object, then the object is undergoing an endothermic reaction. On the other hand, if the surrounding is colder, the object is undergoing an exothermic reaction.
[/quote]
</p>
<p>Yes, I missed the part where you said it was undergoing the reaction. In that case what you said was correct lol.</p>
<p>so, when water (with an initial temperature of 24 celcius) reacts with calcium, producing a solution with a final temperature of 79 celcius, the reaction is exothermic correct?</p>
<p>i think i should explain. yes hudson, energy (heat) is released which translates directly into the temperature increase, since temperature is a measure of the amount of heat. </p>
<p>also just to clear up the confusion abit if anyone's still confused, exothermic reactions result in the products having a lower energy level than the original energy level of the reactants, thus, this energy is released into the surroundings as heat, causing a temp rise. </p>
<p>similarly for endothermic reactions the total energy level of the reactants is lower than that of the product. thus after achieving activation energy level some of this energy is absorbed into the product/bonds/sorry i cant remember. and results in temp decrease (heat is given to surroundings) if you see the graph you'll understand alot more.</p>
<p>oops didnt read watson and crick's explanation but i've written this already so yeah...</p>
<p>Ok i know it’s been a year but i have a chemistry test coming up and i want to make this clear, when you touch two reactions in a jar. One cold and other is hot. Which one is the exothermic and which one is the endothermic reaction? I remember someone saying that if you touch a cold object it is exothermic. It makes sense if the heat was realeased to all the surroundings and then dissipated elsewhere, thus leaving the object itself cold. So is it exo or endo or nothing?</p>
<p>[ul] [<em>] Endothermic - Object will be cold relative to the atmosphere (heat absorbed rather than released)
[</em>] Exothermic - Object will be warm relative to the atmosphere (heat is released) [/ul]</p>
<p>I’ve had trouble with this also. Now I also have to worry about if it is endothermic when breaking or forming bonds. =0 Uh… You obviously need heat to break a bond, so that means it is endothermic, right? But then the surroundings get hotter, so it’s exothermic? AH!!!</p>
<p>The atmosphere obtains energy from exothermic reactions. When chemical bonds form, they have a lower energy potential and therefore release heat upon formation.</p>