Newton's Law of Cooling

The temperature as a function of time for an object is given by Newton's Law of Cooling (this is actually just a good approximation of what happens).

T(t) = Tenv + (Tinit - Tenv)*e-λt

where Tenv is the temperature of the surrounding environment,
Tinit is the initial temperature of the object,
and λ is a measure of how quickly the temperature change occurs.