Calcium Chloride

• Calcium chloride is a water-soluble ionic compound. Consequently, when it is mixed with water, it undergoes a process known as "dissociation," in which it separates into calcium ions (Ca²⁺) and chloride ions (Cl⁻).
  
  

Heat

• Chemical processes either release heat into or absorb heat from their surroundings; these processes are referred to as being either "exothermic" or "endothermic," respectively. Heat is measured in units of joules (J).
  
  

Calcium Chloride + Water

• The dissolution of calcium chloride in water releases 81,350 joules per mole of calcium chloride. Moles of a substance are calculated by dividing by the compound's formula weight (which is 110.98 g/mol for calcium chloride). Therefore, dissolving 1 gram of calcium chloride would release
  
  1g / (110.98 g/mole) = 0.0090 moles calcium chloride
  
  (0.0090 moles) x (81,350 J/mole) = 733 J of heat
  
  

Heat Capacity

• Determining what 733 J of heat actually mean in terms of temperatures requires consideration of water's specific heat capacity, which is 4.184 joules per gram degree Celsius (J/g°C). Therefore, 4.184 joules of heat will increase the temperature of 1 gram of water by 1 degree Celsius. Dissolving 1 g of calcium chloride in, for example, 100 g of water would increase the temperature of the water by
  
  733 J / (100 g x 4.184 J/g°C) = 1.8 °C
  
  

Applications

• In addition to its use in instant heat packs, calcium chloride is widely used as a desiccant (moisture-absorber) because it is capable of absorbing moisture from the air. Some concrete mixes incorporate calcium chloride to decrease drying time.
  
  Calcium chloride is also used as a de-icer. Like sodium chloride (table salt), calcium chloride will decrease the freezing point of water. Thus, ice, which would normally be solid at 0 degrees Celsius, will convert to liquid form if calcium chloride is dissolved in it.