The reaction of an acid with a base, for example, results in the creation of a salt and water. Some, but not all, reactions can be reversed. See nuclear reaction. An action that results directly from or counteracts another action, especially the change in a body's motion as a result of a force applied to it.
Snakes are cold-blooded creatures, just like amphibians. When a certain animal is cold-blooded, it basically means that they are able to adapt their own internal temperature to that of their environment. When a snake is in a cool environment, their body temperature tends to drop rather quickly.
Humans are warm-blooded animals, so are all other mammals, to a certain extent, and birds. However warm blood is not really the question, many reptiles have blood far warmer than ours, but only on hot days. In fact, blood temperature is merely a reflection of body temperature.