IB Chemistry home > Syllabus 2016 > Energetics > Heat energy

Syllabus ref: 5.1

Chemistry deals with observation of the world around us and explanation of the things that happen. When chemical and physical processes happen they often do so with a change in the temperature of the medium, or surroundings. The study of energetics, or thermodynamics, seeks to explain the underlying causes of this phenomenon and to use it to make predictions as to why processes do, or don't occur.

Nature of science:

Fundamental principle-conservation of energy is a fundamental principle of science.

Making careful observations-measurable energy transfers between systems and surroundings.


Essential idea: The enthalpy changes from chemical reactions can be calculated from their effect on the temperature of their surroundings.

Heat is a form of energy. Temperature is a measure of the average kinetic energy of the particles.

Total energy is conserved in chemical reactions.

Chemical reactions that involve transfer of heat between the system and the surroundings are described as endothermic or exothermic.

The enthalpy change (ΔH) for chemical reactions is indicated in kJ mol-1.

ΔH values are usually expressed under standard conditions, given by ΔH°, including standard states.

Applications and skills

Calculation of the heat change when the temperature of a pure substance is changed using q=mcΔT

A calorimetry experiment for an enthalpy of reaction should be covered and the results evaluated.

In Chapter 4.1