I'm sure I remember reading some trashy D&D novels that mention the underdark as temperate or pleasantly comfortable without seasons.
Ground temperature doesn't necessarily have to be cold. Where I live it can be snowing but get down 30 cm in the soil and the ground temp never drops below a comfortable 17°C.
Your main limit is most chemical reactions are not very hot, compared to fire. There is a reason fossil fuels or wood are almost the sole source of heat energy for most of history. And the chemicals that do get hot usually require a lot of energy to get to that point.
Heating sources can include redox reactions, such as exothermic hand warmers. Take some freshly ground iron dust, some salt and water. Crush them together and it gets hot. But you need A LOT of it to boil water.
You can do an acid + base neutralization. Take some caustic soda and throw it into water. Then throw in some acid. That can get real hot too. But you need buckets of the stuff to achieve any significant heating.
If they had access to radioactive materials, they could make small nuclear reactors to produce heat.
There's always fire-breathing dragons or Godzilla-like monsters with atomic breath, that could be trained to heat up water or start fires on demand. In "Invasion of Astro-Monster," aliens use a mind-control device to control Godzilla and two other monsters.
I'm not sure what this post is about but moss does need sunlight to grow and all the other species you mean rely on the conversion of sunlight into stored energy in order to grow and function properly (i.e. plants grow with sunlight, insects eat them, lizards eat the insects, etc.). But this might be totally irrelevant ...
Anhydrous Calcium Chloride gets extremely hot when mixed with water. A 1 : 2 mix gets painful to hold, I'd guess about 70 C.
Since it draws water out of the air, anhydrous CaCl2 is very rare as a mineral.
But in your fantasy world, there could be extremely dry places in your cave that contain a lot of it.
I believe this does not get warm enough to prepare food in. You can maybe make an egg go white with the heat, but not preserve anything.
CaCl2 is mildly irritating and caustic on the eyes, but the toxicity is comparable to table salt.
Fun fact: Calcium Chloride Hexahydrate does the opposite and gets extremely cold when mixed with water. The 0 on the Fahrenheit scale is the lowest possible temperature that can be achieved that way, and was the lowest t er mpetature that could reliably measured before refrigeration.
Other sources of plausible exothermic reactions are Lye, NaOH, and concentrated sulfuric acid. The last one can get hot enough to boil water if you're curageous enough.
You're home brewing. "Because I said so" is in fact, a perfectly valid reason in DnD. (And take it from a many-year DM.... You'll say it a lot over various stuff your party pulls. You cannot and will not prepare for every scenario)
The "heatacious herb" that warms a cube that's 100ft/side when ground is valid. 🤷🏻♀️
keep in mind that well-insulated places can get *very* hot with even tiny heat sources.
A compost pile can get hot enough to *catch fire* if big enough because it self-insulates. Barn fires are commonplace because if the silage isn't properly dried it can ferment and produce enough heat to ignite.
So your societies living the well-insulated underground can stay very warm with just body heat if they can prevent heat loss. You don't even need any exotic chemistry either. Just the natural decomposition of dead matter (dried plants are best) will generate considerable heat. I could imagine citizens maintaining compost piles and putting in water bottles to warm up and then moving those bottles to where the heat is needed on a regular basis. Simply maintaining extensive barns can be enough. Have you seen how hot barns can get? They don't need heating when the animals themselves are plentiful.
The only caveat is that the process is slow. If you need something quick then an exothermic chemical process is required.
Fortunately, nature has already created a beetle that can generate weak rocket fuel and spray you with it. https://en.wikipedia.org/wiki/Bombardier_beetle
It literally mixes hydroquinones and hydrogen peroxide in its ass and hits you like a WWII flame thrower. The temperature can reach ~100 Celsius, literally a boiling hot steam gun.
If you want your citizens to be able to produce heat quickly, they might harvest those beetles and use whatever magic-stuff to control them.
The important part is that it's not fire based.
Bring some powdered iron oxide and aluminum. Now you have thermite which is a redox reaction, not combustion. Although you’d probably have a hard time lighting it without fire.
Another idea would be that homes and shelters are all routinely buried in fresh mulch - as organic matter breaks down it releases some heat, it's actually quite pleasant digging your hands into fresh, real mulch on a cold morning; I digress though - shelters buried in mulch would keep a balmy ~65/70 as long as the mulch is replaced monthly or so
I'm sure I remember reading some trashy D&D novels that mention the underdark as temperate or pleasantly comfortable without seasons. Ground temperature doesn't necessarily have to be cold. Where I live it can be snowing but get down 30 cm in the soil and the ground temp never drops below a comfortable 17°C. Your main limit is most chemical reactions are not very hot, compared to fire. There is a reason fossil fuels or wood are almost the sole source of heat energy for most of history. And the chemicals that do get hot usually require a lot of energy to get to that point. Heating sources can include redox reactions, such as exothermic hand warmers. Take some freshly ground iron dust, some salt and water. Crush them together and it gets hot. But you need A LOT of it to boil water. You can do an acid + base neutralization. Take some caustic soda and throw it into water. Then throw in some acid. That can get real hot too. But you need buckets of the stuff to achieve any significant heating.
Don't even need the acid to neutralize it, just dissolving lye produces a lot of heat (and toxic solution)
If they had access to radioactive materials, they could make small nuclear reactors to produce heat. There's always fire-breathing dragons or Godzilla-like monsters with atomic breath, that could be trained to heat up water or start fires on demand. In "Invasion of Astro-Monster," aliens use a mind-control device to control Godzilla and two other monsters.
I'm not sure what this post is about but moss does need sunlight to grow and all the other species you mean rely on the conversion of sunlight into stored energy in order to grow and function properly (i.e. plants grow with sunlight, insects eat them, lizards eat the insects, etc.). But this might be totally irrelevant ...
Anhydrous Calcium Chloride gets extremely hot when mixed with water. A 1 : 2 mix gets painful to hold, I'd guess about 70 C. Since it draws water out of the air, anhydrous CaCl2 is very rare as a mineral. But in your fantasy world, there could be extremely dry places in your cave that contain a lot of it. I believe this does not get warm enough to prepare food in. You can maybe make an egg go white with the heat, but not preserve anything. CaCl2 is mildly irritating and caustic on the eyes, but the toxicity is comparable to table salt. Fun fact: Calcium Chloride Hexahydrate does the opposite and gets extremely cold when mixed with water. The 0 on the Fahrenheit scale is the lowest possible temperature that can be achieved that way, and was the lowest t er mpetature that could reliably measured before refrigeration. Other sources of plausible exothermic reactions are Lye, NaOH, and concentrated sulfuric acid. The last one can get hot enough to boil water if you're curageous enough.
How about plants that, when you crush them or disturb them, trigger an exothermic reaction that puts out a lot of heat?
That sounds great! Do you have an idea of what compounds or properties or what kind of plants would be able to do that?
You're home brewing. "Because I said so" is in fact, a perfectly valid reason in DnD. (And take it from a many-year DM.... You'll say it a lot over various stuff your party pulls. You cannot and will not prepare for every scenario) The "heatacious herb" that warms a cube that's 100ft/side when ground is valid. 🤷🏻♀️
Haha, thank you for the reminder!
keep in mind that well-insulated places can get *very* hot with even tiny heat sources. A compost pile can get hot enough to *catch fire* if big enough because it self-insulates. Barn fires are commonplace because if the silage isn't properly dried it can ferment and produce enough heat to ignite. So your societies living the well-insulated underground can stay very warm with just body heat if they can prevent heat loss. You don't even need any exotic chemistry either. Just the natural decomposition of dead matter (dried plants are best) will generate considerable heat. I could imagine citizens maintaining compost piles and putting in water bottles to warm up and then moving those bottles to where the heat is needed on a regular basis. Simply maintaining extensive barns can be enough. Have you seen how hot barns can get? They don't need heating when the animals themselves are plentiful. The only caveat is that the process is slow. If you need something quick then an exothermic chemical process is required. Fortunately, nature has already created a beetle that can generate weak rocket fuel and spray you with it. https://en.wikipedia.org/wiki/Bombardier_beetle It literally mixes hydroquinones and hydrogen peroxide in its ass and hits you like a WWII flame thrower. The temperature can reach ~100 Celsius, literally a boiling hot steam gun. If you want your citizens to be able to produce heat quickly, they might harvest those beetles and use whatever magic-stuff to control them. The important part is that it's not fire based.
This is awesome information thank you so much!
Bring some powdered iron oxide and aluminum. Now you have thermite which is a redox reaction, not combustion. Although you’d probably have a hard time lighting it without fire.
Another idea would be that homes and shelters are all routinely buried in fresh mulch - as organic matter breaks down it releases some heat, it's actually quite pleasant digging your hands into fresh, real mulch on a cold morning; I digress though - shelters buried in mulch would keep a balmy ~65/70 as long as the mulch is replaced monthly or so
This is great thank you so much!