Q. What is meant by chemical action being the source of heat?
A. Many things, when their chemical constitution is changed, (either by the abstraction of some of their gases, or by the combination of others not before united,) evolve heat, while the change is going on.
Q. Explain by illustration what you mean.
A. Water is cold, and sulphuric acid is cold; but if these two cold liquids be mixed together, they will produce boiling heat.
Q. Why will cold water, mixed with sulphuric acid, produce heat?
A. Because water (being lighter than sulphuric acid), is condensed by the heavier liquid; and its heat is squeezed out, as water from a sponge.
Q. Why does cold water, poured on lime, make it intensely hot?
A. The heat is evolved by the chemical action, produced by the cold water combining with the lime.
Q. Where does the heat come from?