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We present an application of the Arrhenius law to an unconventional process, the variation of the activity of the Solenopsis ant with the environmental temperature. We believe that students might appreciate this law better if they see it applied to such a process rather than to a simple chemical reaction.
Because ants are poikilothermic (cold-blooded) creatures, their vital processes depend on the environmental temperature. However, it is not easy to specify the reactions that describe the behavior as if they were simple chemical reactions. To obtain a relation between activity and temperature, we measured the speed of ants in their journey toward and away from the nest. Then we adjusted these data to a mathematical model that took into account the Arrhenius equation. We found that the speed toward the nest is greater than the speed away from it, as has been reported by others.
Thermodynamically the increase in the speed toward the nest is associated with a decrease in entropy. This could imply that the signal when ants return to the nest is more intense than the signal when they travel away from it because of the greater concentration of the pheromone in the vicinity of the nest.
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