What is Calorimetry?

Author: Mario Toubes-Rodrigo, Application Specialist, H.E.L Group

Calorimetry is a branch of thermodynamics that deals with heat transfer quantification. Heat can be transferred during a variety of processes, such as chemical reactions, phase changes, or dissolution of solutes in a solvent. Calorimetry follows the first law of thermodynamics, which states that energy cannot be created or destroyed, only transferred. The direction that the heat takes will determine the type of process: if heat is absorbed, the process will be endothermic, whereas if heat is released, the process will be exothermic.

Calorimeters are the device used to study the calorimetry of a process. At their core, calorimeters are insulated containers, allowing for the isolation of the systems under study from their surrounding environment.

Parts of a reaction calorimeter

The energy transferred in a process can be measured using calorimetry, and it follows the equation:

Q = m Cp ΔT

Where Q is the heat, m is the mass of the substance involved, cp is heat capacity of the substance, and ΔT is the change in temperature. The heat capacity is defined as the amount of heat per unit of mass required to increase the temperature by one degree Celsius.

How is calorimetry helpful?

Calorimetry is an invaluable tool for a wide range of applications in science and industry. For example, in the chemical industry, calorimetry is routinely used to determine the potential risks of chemical reactions. Exothermic reactions can result in temperature and pressure inside the reaction where the process occurs. The results of this increase can be catastrophic, like causing explosions. [1] Understanding the calorimetry of the reaction can teach us about the energy that is produced in the exothermic reaction. This knowledge is fundamental in  predicting the maximum temperature the reactor can reach and how dangerous this process can be. It will help us answer questions like: will the fluids in the reactor boil and increase the pressure in the reaction? [2] Or will the chemicals in the reactor decompose, generating hazardous substances? With this information, measures can be implemented to avoid dangerous situations.

Another field in which calorimetry shines through is battery safety. Batteries can be exposed to high temperatures, sometimes due to environmental conditions of charge/discharge processes. This is particularly relevant for some lithium-ion batteries (LIBs) where the electrolyte can decompose at high temperatures, resulting in highly flammable gases. The cathode, normally a metal oxide, also is susceptible to decomposition at high temperatures, producing O2. The combination of high temperature, O2, and organic gases can result in fires. Just in London, there are fires linked to batteries in e-scooters or e-bikes every two days[3]. To avoid this, testing protocols, such as heat-wait-search, [4] are fundamental.

In this case, batteries are heated in a calorimeter to study their thermal behaviour. If decomposition processes occurred, batteries would heat up, and an increase in temperature would be observed in the calorimeter. The knowledge acquired by these studies allows for understanding where the safety limits are and what were the consequences of potential failures.

The multiple faces of calorimetry

These are only two examples, but calorimetry applies to other fields of the science industry: in biology, studying metabolic processes, or in the food industry to calculate the caloric content of food. It plays a crucial role in material science, understanding phase changes, and, in studying weather and climate phenomena in environmental science. So, despite looking simple, we can see that calorimetry constitutes a fundamental tool to obtain insight into the thermal properties of substances and heat changes in chemical reactions. It plays a crucial role in understanding energy flow in physical, chemical, and biological systems. With technological advancements, the scope and precision of calorimetry continue to improve, offering even more detailed insights into the complex world of energy exchange.

References

  1. Maharashtra fire: Three die as chemical reactor explodes at industrial unit in Tarapur, The Indian Express
  2.  Critical Considerations in Process Safety, H.E.L Group
  3. Electric bikes and scooters cause a fire every two days in London, The Times
  4. Heat Wait Search Video Using H.E.L Battery Testing Calorimeters (BTC), YouTube

H.E.L Group

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