Calorimeter
Definition and meaning of Calorimeter in chemistry.
A calorimeter is a device used to measure the quantity of heat absorbed or released during a chemical reaction or physical change.
In more detail
It works by isolating the reaction in an insulated container and measuring the resulting temperature change in a surrounding medium of known mass and specific heat capacity, usually water. That temperature change is converted to heat using q = mcΔT, which can then be used to calculate the enthalpy change of the reaction. Two common designs are the constant-pressure coffee-cup calorimeter, used for reactions in solution, and the constant-volume bomb calorimeter, used for combustion reactions carried out under high oxygen pressure in a sealed steel vessel.
Key facts
| Field | Physical Chemistry |
|---|---|
| Key equation | q = mcΔT |
| Common types | Bomb calorimeter (constant volume), coffee-cup calorimeter (constant pressure) |
| Measures | Heat of reaction, combustion, or phase change |
A bomb calorimeter is used to burn a weighed sample of glucose completely in oxygen; the temperature rise of the surrounding water bath is measured and used to calculate the heat of combustion of glucose.
Frequently asked questions
What is the difference between a bomb calorimeter and a coffee-cup calorimeter?
A bomb calorimeter operates at constant volume in a sealed rigid vessel and is used for combustion reactions, measuring internal energy change (ΔU). A coffee-cup calorimeter operates at constant (atmospheric) pressure and is used for reactions in solution, measuring enthalpy change (ΔH) directly.
Why must a calorimeter be well insulated?
Insulation minimizes heat exchange with the surroundings so that the measured temperature change reflects only the heat released or absorbed by the reaction being studied, giving an accurate result.