Prior to the nineteenth century, the transfer of heat was assumed to be due to the flow of a substance called caloric, an invisible, weightless fluid whose total quantity remained constant. The caloric theory subscribed to the belief that an object became hot when it was permeated by a large quantity of caBeaker with liquid. Beaker with liquid.Beaker with liquid.Beaker with liquid.Beaker with liquid.Beaker with liquid.Beaker with liquid. loric and cooled when some of its caloric flowed into other objects that had less caloric. This model was upset by the work of two scientists: Benjamin Thompson (later known as Count Rumford) and James Joule. Rumford supervised the boring of cannons. He noted that the water kept in the bores to prevent overheating boiled continuously. This boiling was supposedly caused by the caloric that flowed from the metal of the cannon as it was cut.

From his observations, however, Rumford deduced that this explanation could not be correct because the boiling continued even when the boring tool became so dull that it no longer had any effect on the metal. Apparently, the caloric was being produced out of nothing. Rumford concluded that it was the work needed to turn the dull tool, instead of caloric transfer, that was being converted into heat. In a series of experiments, Joule showed that a given amount of mechanical work always produced the same amount of heat no matter what kind of mechanical work was done. This demonstration established that heat is indeed a form of energy. Today, it is known that heat is energy contained in the random motion of atoms and molecules and that to heat an object is to increase the energy so stored.

Although students will not be exposed to kinetic molecular theory until high school, teachers who understand the following points will be better able to discuss the subjects of heat and heat transfer. The transfer of heat from a warmer object to a colder object is referred to as heat flow. Heat may be transferred by conduction, convection, or radiation. Standard Sets 3 and 4 in grade six deal in depth with the relationships between heat and convection in Earth’s mantle, oceans, and atmosphere. Material covered in those standards will build a foundation for the study of heat. Students will learn that atoms are free to move in different ways in solids, liquids, and gases and that heat may be given off or absorbed during chemical reactions. The concept that heat is a form of energy associated with the motion of atoms and molecules is covered in high school. Students in grade six will study the relationship between work and heat flow and will be required to solve problems related to this subject.