Question

Can someone please paraphrase this to me.... if possible.

Heat effects of chemical or physical processes can be measured in a calorimeter. Instruments of widely varying designs are employed to accommodate the large range of experimental conditions encountered. For instance, the heat effects to be measured may range from milliJoules to milliliter, quantities involved from fractions of milliliters to hundreds of milliliters and from milligrams to grams, operating temperatures from below liquid helium temperature (4.2 K) to 2000o C, and pressures from atmospheric to thousands of atmospheres. Isothermal calorimeters measure the heat evolved by determining the heat that has to be added or taken out in order to keep the temperature of the system exactly constant. Adiabatic calorimeters measure the heat evolved by registering the temperature increase or decrease of a system that is ideally insulated such that there is no extraneous heat exchange (loss or gain) between the system and its surroundings (i.e. q = 0).

Chemical changes can result in the release or absorption of heat and/or work being done on the system or by the system on the surroundings. This is expressed by the first law of thermodynamics: ΔU = q + w (1) The main feature of the bomb calorimeter is that it is adiabatic (no heat is transferred to or from the outside), and that the volume does not change in the combustion process. This means that from the first law of thermodynamics, w = 0, and therefore the measured heat effect of the reaction, q, equals the change in energy of the reaction, ΔUrxn : qv, rxn = ΔUrxn (2) In the bomb calorimeter (Figure 1), the system is contained within the bomb combustion chamber. When the sample combusts, energy is transferred from the system to the surrounding water in the bucket, and a change in the temperature of the water is observed. The bomb combustion chamber and bucket of water are further contained within a calorimeter jacket. This jacket serves as a thermal shield, controlling any heat transfer between the bucket and its surroundings (i.e. the lab), in other words, the jacket serves to minimize heat flow to the surroundings and thus provides the quasi-adiabatic conditions in this experiment.

Can someone please paraphrase this to me.... if possible.

Answer 1

Chemical or physical process's Heat effects can be measured in a calorimeter.Various instruments are used to accommodate the large range of experimental conditions. For instance, the heat effects to be measured may range from mJ to ml, quantities involved from fractions to hundreds of ml, operating temperatures from below 4.2 K to 2000o C, and pressures from 1 atm to thousands of atm. Isothermal calorimeters measure the heat evolved by determining the heat that should be added or removed so that temperature of the system is constant. Adiabatic calorimeters measure the heat evolved by registering the temperature increase or decrease of a system that is ideally insulated such that there is no external heat exchange between the system and its surroundings (i.e. q = 0).

Chemical changes can result in the exchange of heat and/or work being done.This is expressed by the first law of thermodynamics: ΔU = q + w

(1) The main feature of the bomb calorimeter is that it is adiabatic (no heat is transferred to or from the outside) and that the volume is constant. This means that from the first law of thermodynamics, w = 0, and ΔUrxn = q

(2) In bomb calorimeter, the system is contained in a combustion chamber. When the sample combusts, energy is transferred from the system to the surrounding water in the bucket, and a change in the temperature of the water is observed. The bomb combustion chamber and bucket of water are further contained within a calorimeter jacket. This jacket serves as a thermal shield, controlling any heat transfer.

The jacket minimizes heat flow to the surroundings and thus provide a quasi-adiabatic condition in this experiment.