Calorimetry (Eduqas Chem, AQA CHem, OCR B Chem)

Seite 1

Introduction to Calorimetry

Calorimetry is a technique used to compare the different amounts of heat released by substances when they are burnt.

It involves measuring the temperature change in a glass or metal container of water.

Energy is usually measured in joules(J), but can also be measured in calories.

\(4.184cal = 1J\)

(You do not need to remember this conversion factor)

Heat capacity: The amount of energy required to change the temperature of an object by 1 degree.

Therefore, if we know the heat capacity of the water and container, and we measure its temperature change, we can calculate the energy given out by burning a substance.

\(c\times \Delta \Theta = \text{Energy change}\)

\(c\) is the heat capacity of the water and its container

\(\Delta \Theta\) (Pronounced 'del-ta thee-ta') Temperature change of the water, measured in degrees

The energy released by the substance when it is burnt can then be quoted in kJ or calories for a given mass or amount of

substance, eg calories per gram, kJ per mole or kJ per gram.

Energy released by a Chemical Reaction

The amount of energy released or absorbed by a chemical reaction in solution can be calculated from the measured temperature change of the

solution when the reagents are mixed in an insulated container. This method can be used for reactions of solids with water or for neutralisation reactions.

Seite 2

Energy released when burning a fuel