Can dissolving minerals affect water temperature?

AI Thread Summary
Dissolving various minerals, molecules, and salts in water can significantly affect the temperature of the solution. Many salts exhibit a negative heat of dissolution, meaning they release heat when dissolved, particularly during the hydration process where water molecules surround the ions. For example, the dissolution of calcium oxide (quicklime) in water is highly exothermic and can generate substantial heat, making it useful in self-heating products. In contrast, the dissolution of salts like lithium chloride is also exothermic, while sodium chloride has a negligible effect on temperature, and potassium chloride is endothermic, cooling the water. The temperature change during dissolution is influenced by the balance between the lattice energy of the salt and the energy released from forming solvation shells around the ions. Understanding these interactions is crucial for predicting temperature changes in solutions.
RICKYtan
Messages
23
Reaction score
0
Are there any type of minerals/molecules/elements even solids that when dissolved, in say a glass of room temp water, can raise or lower the temperature? Examples...
 
Chemistry news on Phys.org
Nearly everything, and especially salts, many chemicals will cool the water while getting dissolved. Breaking up the bonds in whatever gets dissolved needs some energy, that energy is taken from heat.
 
Last edited:
mfb said:
Nearly everything, and especially salts, will cool the water while getting dissolved.

Sorry but no. Many salts (and by many I mean something in a "half" ballpark) have quite a large, negative heat of dissolution. My bet is that you are missing the hydration (or more generally solvation) part - capturing of dipole water molecules by cations and anions. That produces quite a lot of heat, especially when dissolving anhydrous salts.
 
One well known reaction is Calcium Oxide with water . The uncontrolled reaction is quite violent and large amounts of heat are generated .

The reaction can be calmed down a bit if necessary by use of passive additives or by controlling the rate at which the Calcium oxide and water are brought into contact .

This is one of the heat generating reactions used in products like self heating soup .

Calcium Oxide is commonly called Quicklime .
 
The CaO reacts with water beyond simple dissolution. The classic heat of solution experiment is to dissolve the series LiCl, NaCl, KCl in water. LiCl dissolution is very exothermic (water gets very hot), NaCl basically leaves temperature unchanged, and KCl dissolution is quite endothermic (water gets very cold, enough to form frost on the reaction vessel even in small demonstrations). The reason, as @Borek mentioned, is the balance of the salt’s lattice energy with the energy gained by forming a solvation shell of water molecules around the ions.
 
  • Like
Likes jim mcnamara
Borek said:
Sorry but no. Many salts (and by many I mean something in a "half" ballpark) have quite a large, negative heat of dissolution. My bet is that you are missing the hydration (or more generally solvation) part - capturing of dipole water molecules by cations and anions. That produces quite a lot of heat, especially when dissolving anhydrous salts.
Roughly half? Okay, then I misremembered it. I know about the hydration, but I expected it to be smaller for most salts.
 
mfb said:
Roughly half? Okay, then I misremembered it. I know about the hydration, but I expected it to be smaller for most salts.
Individual Ion-ion interactions are significantly stronger than the individual ion-dipole interactions in water solutions, but in solution, you have 4-8 waters tightly bound to each ion, and a few dozen more loosely bound to this inner hydration shell structure, so you can pick up energy pretty quickly in these situations.
 
Back
Top