[harvester of sorrow]

What reaction happens when ammonium bicarbonate, NH₄HCO₃, is heated? The ammonium bicarbonate started, like, bouncing off the spoon, but what is it that makes it do this? And is this an exothermic or an endothermic reaction?

[Arkcon]

What reaction happens when ammonium bicarbonate, NH₄HCO₃, is heated?

Doing this is hard to predict, with limited information.  However, we can work with it step by step and find out as much as we can.

The ammonium bicarbonate started, like, bouncing off the spoon, but what is it that makes it do this?

What indeed.  Can you make any sort of guess?  Compounds don't have legs, and can't really "jump".  But something made it move ... what did you see make it more?  Or what didn't you see, that made it move?

And is this an exothermic or an endothermic reaction?

Well, can you define each, and see which definition matches procedures and results, and answer this one for yourself?

Sorry to ask you a bunch of questions.  But we don't dump complete answers to classwork on this forum.  We try to help people help themselves, its in the Forum Rules, posted in red, at the top of each page.

[harvester of sorrow]

After rethinking I realized the endothermic/exothermic thing (which really was pretty easy ).

The "bouncing" must have something to do with the temperature increase, the adding of energy; obviously ΔS is positive, but I'm still a bit unsure of what actually makes them move like that...

[gelminil]

NH4+ is an acid and HCO3- is a base.  Heating this will give
NH3 (should be able to smell some ammonia)
also H2CO3 which actually decomposes instantaneously to H2O and CO2.  It is jumping around owing to release of two gases.
Might actually hear some cracks if it is more crystalline - (crack cocaine has a similar reaction when heated releases a gas and cracks)

[cheese (MSW)]

gelminil Your answers so far have been very good -excellent, but we try not to spoon-feed students with the answers.
So my answer to this question might have gone something like this: write out a balance equation
for the decomposition and consider the physical state of the products and the jumping starting xtls. 
Hint: (NH4)2CO3 (ammonium carbonate) is used in smelling salts.
If the student subsequently goes to Wikipedia to look up smelling salts I think we have still done our job.

[Dan]

gelminil Your answers so far have been very good -excellent, but we try not to spoon-feed students with the answers.

Indeed. gelminil, a reminder of the forum policy:

Rules and Policy: To Replyers

Chemical Forums members subscribe to the Socratic Method of learning; where by students can ask a question and learn the answer for themselves from the gentle prodding and questioning by forum staff and regulars. Don't give the final answers, let students solve questions on their own. If you will be answering student questions please follow the Socratic Method too. This isn't rigorously enforced and not all answers have to be in the form of a question, but all answers should be within the spirit of the Socratic Model.

Cheers