# Calorimetry

## Calorimetry

Calorimetry is the field of science that deals with the measurements of the state of a body with respect to the thermal aspects in order to examine its physical and chemical changes. The changes could be physical such as melting, evaporation etc. or cloud also be chemical such as burning, acid – base neutralization etc. calorimeter is what is used to measure the thermal changes of a body. Calorimetry is applied extensively in the fields of thermochemistry in calculating the enthalpy, stability, heat capacity etc.

Experiment to measure Specific heat of water:Calorimetry is an experimental technique for the quantitative measurement of heat, exchange. We know that heat flows from a hot body to a cold body. When the two bodies are isolated form their surroundings, the amount of heat lost by hot body must be equal to the amount of heat gained by the cold body. The same principle is used in calorimetry.

As heat is energy in transit, this principle is really just conversation of energy. Calorimetry, dealing entirely with one conserved quantity, is in many ways the simplest of all physical theories. One of the important uses of calorimetry is the determination of specific heats of unknown materials. A Calorimeter is a device used to measure the amount of heat exchange.

It is important that the calorimeter be well insulated so that almost no heat is exchanged with the surrounding. In the technique known as “Method of Mixtures”, a sample of the substance is heated to a high temperature which is accurately measured. The substance is then placed quickly in the calorimeter containing known as mass of water at known temperature. The contents are stirred constantly until the mixture attains the final common temperature. The heat lost by the substance will be gained by the water and the calorimeter.

Let

m₁ = Mass of water in the Calorimeter,

m₂ = Mass of the substance,

mc = Water equivalent of the Calorimeter,

T₁ = Initial temperature of water and Calorimeter,

T₂ = Initial temperature of the substance,

T = Final temperature of the mixture,

Cs = Specific heat of the substance,

Cw = Specific heat of water.

Heat lost or gained by a body is given by = mcΔT

Therefore,

Heat lost by the substance = m₂ Cs (T₂ – T)

Heat gained by water and calorimeter = m₁ Cw (T – T₁) + mc Cc (T – T₁)

According to the law of heat exchange:

Heat lost = Heat gained

m₂ Cs (T₂ – T) = m₁ Cw (T – T₁) + mc Cc (T – T₁)

∴ $${{C}_{s}}\,=\,\frac{({{m}_{1}}\,{{C}_{w}}\,+\,{{m}_{c}}\,{{C}_{c}})\,(T\,-\,{{T}_{2}})}{{{m}_{s}}\,({{T}_{2}}\,-\,T)}$$.

The need for Calorimetry: It is well known now that the matter is always obeys the principle of lowest energy i.e. given the option, matter will exist in the lowest energy state possible. Despite this, matter can have a variety of energetic states. Uranium atoms, for example, are a powerhouse. Energy of matter has a profound effect on its natural occurrence and its reactivity etc. if we can unravel the relationship between them then we can predict natural occurrence, reactivity and physical properties based on the energy measurements, we make through calorimetry, understanding the thermodynamics properties of a substance will inevitably yield answers to structure and other properties.