When we studied the concepts of thermal equilibrium of two or more substances, we saw that if these bodies of different temperatures are brought into contact, after some time they reach the same temperature. The explanation for this phenomenon has been proposed for a long time based on a model called caloric. In this model, it was said that all bodies possessed, inwardly, the caloric, which was a fluid and invisible substance with negligible weight.
Also in this model, it was said that the higher the body temperature, the more calories it had inside. Therefore, when two bodies with different temperatures were placed in contact, the passage of more calories from the body occurred. warm to the colder body, causing a decrease in the temperature of the first and an increase in the temperature of the second body. In this way, the caloric flow only stopped when the bodies reached thermal equilibrium. The caloric idea did not last long, being soon replaced by another more plausible theory, in which the heat it is considered as a form of energy.
Today we know that Heat is the energy transferred spontaneously from one body to another, solely due to a difference in temperature between them. We also know that when we put two bodies with different temperatures in contact, thermally isolated from the environment, after some time we notice that they are in thermal equilibrium. Therefore, we can conclude that there was a transfer of energy from the “hotter” body to the “coldest” body, until both had the same temperature.
In order to study the heat exchanges between two or more bodies, especially when one of them is in a liquid state, it is convenient have a suitable container, which allows to obtain, directly or indirectly, the value of the amounts of heat exchanged between the bodies. This type of container, which facilitates the thermal contact between the bodies and makes the exchange of thermal energy with the external environment difficult, we give the name of calorimeter.
Therefore, we can generally say that every container that is thermally insulated from the external environment is a calorimeter. The calorimeter can be used to determine the specific heat of substances. Generally, water is poured into its interior and, after a short period of time, the system is in equilibrium thermal, you place a body you want to study inside the water, with an initial temperature different from the system water-calorimeter. The figure below shows a basic example of a calorimeter.
By Domitiano Marques
Graduated in Physics
