gatewaycityca - 8-2-2014 at 04:55
Hi,
I just joined this site, and I'm hoping someone can help with a question I had. I've always been fascinated with science, ever since I was a little
kid, but don't know much about chemistry. I've become interested in it recently though, and I've been doing a little bit of reading.
I want to do some experiments with exothermic reactions. It needs to be something safe (won't catch fire or explode!) and using cheap, easy-to-find
chemicals or substances. I'm basically just looking for a relatively mild reaction, like something that will heat up water to around maybe 100
degrees F or so. Hopefully, it would be something that starts to react fairly quickly, but is able to stay warm/hot for a while.
I've been searching everywhere on Google, and so far I've tried mixing hydrogen peroxide with yeast, and hydrogen peroxide with bleach. The first
experiment (just pouring the peroxide in a small cup with the yeast) worked well and got hot, but it doesn't last very long and yeast would get really
expensive in the quantities I'd want. The second little experiment I did, mixing peroxide with bleach in a cup worked great too (even diluted with
water). It got surprisingly hot, and it didn't seem to get too violent. But I didn't really like working with bleach, only because I was worried
about ruining my clothes!
I've also read something about iron filings mixed with vinegar or hydrogen peroxide causing a reaction. But is it just as simple as putting the iron
powder in a cup with peroxide or vinegar?
So any ideas...something that will get hot, but not violent?
Thanks in advance guys! 
- Chris
Random - 8-2-2014 at 04:58
Check for sodium acetate hot ice on nurdrage channel.
blogfast25 - 8-2-2014 at 06:39
"Hopefully, it would be something that starts to react fairly quickly, but is able to stay warm/hot for a while."
The latter only depends on how well you insulate your reactor.
Dissolve waste aluminium in strong acids like sulphuric of hydrochloric acid. Lots of heat is generated. Can lead to thermal runaway if the
concentrations are high.
This belongs in 'beginnings'.
BromicAcid - 8-2-2014 at 06:47
Classic example of large scale chemical reaction to produce exotherm for the purpose of heat is the hydration of calcium oxide (quick lime). This has
been used for years in self-heating / self-cooking products where a packet of water is burst and hydrates the calcium oxide to create heat. It also
has the benefit of being cheap. As for long durations, water has a high specific heat, it will hold a lot of heat and release it over time, but don't
expect a miracle. Chemical reactions speed up as they are heated so unless you have some sort of time release method then your reaction is going to
go faster until it is complete then cool naturally, not a gradual release of heat.
Zyklon-A - 8-2-2014 at 07:56
100 degrees F? That's not very warm at all, about the temp of my swimming pool in the summer, colder than you shower most likely. Limiting yourself to
temperatures only that high is not going to be very exciting, aluminum in acid (HCl is cheapest) will bring the temperature to the boiling point of
the acid. (20% HCl boils at 108°C, concentrated acid boils only at 48°C)
gatewaycityca - 8-2-2014 at 12:51
Thanks for the replies so far. 
Zyklonb, 100 degrees F was just a real broad estimate. Basically, I want something that will get pretty hot but not hot enough to melt plastic or
cause burns. I don't need anything too exciting...I just need it to get hot.
I also don't want anything that would release toxic fumes. (I don't really care if it has a little bit of a strong smell to it, just as long as it's
not actually toxic).
I'm leery about using acids, because of fumes. One reason I decided to try hydrogen peroxide and bleach was because I read the result was just oxygen
and saltwater. I am open to trying acids or other chemicals though as long as there aren't any dangerous fumes released in the reaction.
I'm sorry guys, I know this is pretty vague. But I'm just looking for a way to make water hot with a chemical reaction, but in a way that is
reasonably safe...nothing that would release poisonous fumes and nothing that could go KABOOM. lol.
Also, preferably something that is very common and fairly cheap.
BromicAcid, Calcium oxide might be a good idea. Where can I get it, and how hot would you expect it to reach?
[Edited on 2-8-2014 by gatewaycityca]
[Edited on 2-8-2014 by gatewaycityca]
Zyklon-A - 8-2-2014 at 13:23
If you're scared of acid fumes, stay away from concentrated HCl (when heated.) Concentrated sulfuric acid will give out no fumes unless it gets
>300°C. But it is quite corrosive, so be careful and wear gloves.
[Edited on 8-2-2014 by Zyklonb]