Endothermic reactions

fozzle

I was asked some time ago if I could come up with any examples of endothermic reactions (for a teacher-friend to tell her students) and all I could come up with was sherbet and water. Are there any other simple examples ye can think of? I'm sure there must be something but I'm drawing a blank.

Thanks.

YFlyer

Photosynthesis.

Professor_Fink

fozzle wrote: »

I was asked some time ago if I could come up with any examples of endothermic reactions (for a teacher-friend to tell her students) and all I could come up with was sherbet and water. Are there any other simple examples ye can think of? I'm sure there must be something but I'm drawing a blank.

Thanks.

Salt and water also works.

Azelfafage

The Fridge.

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Professor_Fink

Azelfafage wrote: »

The Fridge.

.

No. That's not a chemical reaction, it relies instead on a phase transition.

Azelfafage

If the goings-on inside a Freezer are not "chemical" then I am a Dutchman.

Or maybe a Martian.

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Professor_Fink

Well in that case, hallo, en welkom op ons land.

Azelfafage wrote: »

If the goings-on inside a Freezer are not "chemical" then I am a Dutchman.

Or maybe a Martian.

.

Azelfafage

There is an interesting example in the Periodic Table of the elements.

Iron is the most stable element of all..it sits in the middle of the table.

To create an element lighter than iron you subtract energy.......Exothermic.

To create an element heavier than iron you have to add energy........Endothermic.

(This is why ordinary stars cannot make elements heavier than Iron........
That takes a supernova.)


And VICE VERSA

So we FUSE Hydrogen Atoms,creating Helium, to create a Hydrogen Bomb...exothermic.

At the other end of the periodic table we do the very opposite.

We SPLIT the heavy elements Uranium or Plutonium to create an Atomic Bomb...exothermic.

Uranium,for instance, was created in Supernovae from lighter elements by ENDOTHERMIC nuclear fusion reactions.

That is why splitting a Uranium atom apart releases so much energy.

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Professor_Fink

Azelfafage wrote: »

There is an interesting example in the Periodic Table of the elements.

Iron is the most stable element of all..it sits in the middle of the table.

To create an element lighter than iron you subtract energy.......Exothermic.
...

That is complete and utter nonsense. You are conflating nuclear stability with chemical reactions.

You also seem to neglect Helium.

Azelfafage

Helium was created in the Big Bang.

I was not just neglecting Helium Professor Fink.

Several of the elements with atomic weight less than Iron can only have been created in a Supernova.

ALL of the elements heavier than Iron HAD to be created in a Supernova.

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Professor_Fink

Azelfafage wrote: »

Helium was created in the Big Bang.

I was not just neglecting Helium Professor Fink.

What I meant was that you neglected the fact that the Helium nucleus is an island of stability. Nucleii to either side of it are much less stable.

Azelfafage

Mea Culpa.

I was balancing a laptop on my knees in Dusseldorf Airport when I described Iron as the "most stable element".

I was wrong.

All I meant to say was that Iron is at the bottom of an energy well.

In creating Helium from Hydrogen there is an enormous release of energy.

I described this as "exothermic".

This applies to all elements "lighter" than Iron.

To create elements elements heavier than Iron,from LIGHTER elements requires an INPUT of energy.....Endothermic.

A Uranium atom is a little "battery" with endothermic energy sucked out of a Supernova.


Split a Uranium atom with a fast neutron and that energy will re-emerge.

Ask the people of Hiroshima.

That's all I was saying.

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craggles

Eh, what?

fozzle

Professor_Fink wrote: »

Salt and water also works.

Just thinking about this - surely salt and water isn't a reaction? It's a solution?

ravydavygravy

Google is your friend:

http://chemistry.about.com/od/lecturenotesl3/a/endorxns.htm

SOL

Salt and water isn't a chemical reaction, but it is endothermic, infact many salts dissolve endothermically, another excellent trick for experiencing something endothermic is adding either salt or ethanol to ice...