Want a chemical that heats up when mixed with water

A. Hi cousin Naveed. Is your question how to initiate the reaction after some stipulated time -- like how to build some sort of mechanical or chemical timer?

What is this device made of, what is its purpose and function, and what range of time delay do you seek. Thanks!

Regards,

A. Jake Blade, James Watts, Willie Alexander, and Geoff Smith have already generously volunteered their time answering that question. Please request clarification of anything that was said that is confusing you, or comment on anything that you disagree with, rather than starting over. Thanks!

Regards,

A. Caution:
Sodium acetate and water
NaOH + NaHSO4 => Na2SO4 + H20 (ends up with water)
Steel wool and Table salt and a little water
Sodium , Lithium, even Tritium.

I have used all of these in many different situations. And maybe a few others. My caution is don't try to get a 5 or 6 second reaction with a massive BTU output. usually if it goes right it soon ends up dangerous and wrong. it can be compared to nuclear reactions. slow is good and controllable and fast is BOOM.

A. Hi Bhargav. There is no chemical that is perfectly safe to eat or drink in unlimited quantity. But Geoff and others have mentioned heating agents that have been included in food and where to find more info about them. If those references didn't answer your question, please carefully detail exactly what scenario you have in mind and ask for clarification about the particulars. Thanks!

Regards,

A. Hi again. Alkali will attack and destroy aluminum; it has essentially no bad effect on steel.

Regards,

Hi Bhargav,

'Alkaline' isn't any specific substance; it's a descriptor for substances with a pH above neutral in water, or with the ability to counteract acidity, so there is no answer to your question until you ask it in a more precise way.

I get the feeling you are bringing this up because of that whole 'alkaline water' health fad -thanks in part to Gwyneth Paltrow for the 'expert' advice that also includes sticking coffee up your bum, so take her [utterly stupid oops did I say that out loud?] advice with a grain of salt... wish she'd just stick with acting...
IMVHO the alkaline water craze, which also apparently requires you to own a fancy 'alkaline water bottle' that costs a minimum $50 USD, is just about the stupidest cash grabby joke played on consumers since the days of the snake oil salesmen. I mean, your digestive system only works because of the strongly acidic environment your body creates, and by the time your 'alkaline water' gets past your stomach, it sure ain't alkaline any more!!

But back to the question at hand. What is your source of alkalinity? What is your can made of? And how strong a solution are you trying to make?

If you add sodium bicarbonate to water and store it in a can made of stainless steel it's a VERY different situation than adding lye to water and storing it in a can made of aluminum (which won't be a can for long!), and so on, even though both examples are in line with your question. I don't even want to say which one is safer because I don't want to encourage this trend!!! But sodium bicarb is just baking soda and goes in food all the time and won't react with stainless... might not taste the greatest but a pinch in your water bottle won't kill you. Maybe a little weirdly salty. Eww have fun with that lol!

Please, without a basic understanding of chemistry, don't try to make DIY health drinks (of dubious value) out of substances you don't understand completely. You can harm yourself badly. Please don't fall for the alkaline water silliness, watching these health fads come and go when good nutrition is already right in front of us... it just hurts my head and actually makes me wish for the old days (by which I mean probably last month ?) when we at finishing.com just tried to figure out how to get that black stuff off those bank notes... ;)

A. Thanks Rachael, good advice. 'Nature' just retracted a 1988 article they published which had made claims about structured water. Apparently the world agrees with you. But I think Bhargav wants to use an alkaline material to self-heat water based on his earlier posting.

BTW, some of those people with black banknotes aren't as credulous as you think. Many of them understand that most of the stuff in the trunk is just black paper; they just know that their real money is still mixed in with it and they just want that portion cleaned. The scammers couldn't possibly have left with their money because they kept it under watchful eye :-)

Regards,

A. Hi Avery,

Anhydrous copper sulphate [on eBay or Amazon](CuSO4) will heat up rapidly when water is added to it forming CuSO4·5H2O.

A small amount of it (half a teaspoon) with about that much water should heat up enough that it becomes too hot to handle (as my chemistry teacher once demonstrated using an unfortunate volunteer).

You can acquire anhydrous copper sulphate by heating up CuSO4·5H2O in a crucible over a bunsen burner. It should go from blue crystals to white-grey powder.

You could vary the amount of CuSO4 and water to control the temperature it reaches.

Double check with your science teacher that it is indeed safe, but as far as I'm aware it is relatively safe to work with as long as you wear your safety glasses and gloves.

A. Hi Robert. An interesting concept, but a remaining problem is that such a "jump start" is a drop in the bucket. The latent heat of vaporization of water is 970 BTU/lb. whereas raising that pound of water all the way from 33 °F to 212 °F takes 179 BTU/lb., so even if you were able to achieve total efficiency in your process, the best you could hope for is supplying a small fraction of the necessary heat.

But, yes, chemically heating the water could get you started sooner. Still, considering the scaling you would have to expect from any such chemical, and the limited advantage of hot water, I think you'd find it more practical to plan on just instantaneously heating a tiny slipstream of the water, rather than preheating all of it.

Regards,

 Thanks, these comments were very helpful.

Hi Akshay. Welcome! But sorry, simply starting over 3 years and 60+ postings later usually achieves nothing but delivering the kiss of death to a posting because people have already invested a lot of their time & effort on detailed responses. So, instead, please try to keep it interesting by explaining exactly what idea you have in mind, and by asking for clarification on something someone has posted. Thanks!

Regards,

Hi Mohit. Tell us what you're up to please, and interest & consequent responses may develop.

Luck & Regards,

A. Hi Noah. I don't believe there is any such chemical. Calcium oxide (lime) is used in self-heating cans, even self-heating meals, but it is kept separate from the food. Food products must be carefully chosen and inspected; you can't just mix chemicals, even much safer ones, into something you will eat or drink.

But your teacher doesn't want you to ask someone for the answer, s/he wants you to read and think. If you read & study this thread, and follow a few links it suggests, I think you'll have an excellent understanding of the whole subject.

Luck & Regards,

A. Hi Panthera. Don't feel bad for not understanding it :-)

You'll learn as you continue your chemistry and physics studies that nobody fully understands such things; our knowledge is always a simplified model of reality. The models get better & more detailed as we learn more, but remain simplified models. And as one of the world's greatest physicists & teachers, Richard Feynman (dec.) said, 'Ask me how something happens, never ask me why'.

So how does sodium hydroxide, NaOH, heat up when water, H20 is added? You can look up 'heat of liberation', and 'protonation', for a deeper understanding of the reaction that occurs in the molecules as water and NaOH mix, or you can simplify it to 'the dilution breaks chemical bonds, releasing energy'. Or you can view chemical reactions as batteries that you charge and discharge, or boulders that you can roll up and down hills, recognizing that just as it takes energy to concentrate NaOH (get the water back out of it), it releases that energy when you let the water back in.

Luck & Regards,

A. Hi Ian. The basic problem is that there is no free lunch and no perpetual energy machines. In nature, things always degenerate to their lowest energy state. That's why you don't find iron & steel in nature, you find rust.

If you have an energy source, then you can use it to create chemical compounds that will release energy, but you can't get out as much energy as you put in. It's the same problem with hydrogen energy for automobiles; you can burn hydrogen and power a car without generating any carbon dioxide, but separating water into hydrogen & oxygen requires more energy than you get out from burning the hydrogen.

In the end, the only energy source appears to be nuclear energy -- either created here on earth, or created in the sun and harvested here as solar power, wind power, hydro power, geothermal power, or burnable hydrocarbons.

Luck & Regards,

Many thanks, Ted. I appreciate your replying and so soon. Ian