How does water kept in an earthen pot become cool during summer?

A3 year-old is brought to the burn unit after pulling a pot of hot soup off the stove and spilling it on herself. she sustained 18% second degree burns on her legs and 20% third degree burns on her chest and arms. total body surface area burned is 38%. what icd-10-cm codes are reported for the burns (do not include external cause codes for the accident)?