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See also Advanced A Level Energetics–Thermochemistry – Enthalpies of Reaction, Formation & Combustion

and enthalpy calculations from calorimetry data for Advanced A Level chemistry students

Advanced A Level Energetics INDEX of revision notes on thermochemistry, enthalpy, entropy etc.

0. Introduction to energy changes in chemistry

Energy changes are an important facet of chemical reactions. The interaction of molecules or ions often involves changes in energy due to the breaking and forming of bonds. Chemical reactions which release energy are called exothermic reactions, and those that take in (absorb) heat energy are endothermic. These energy transfer changes produce heating or cooling effects that can be used in a range of everyday applications.

Interactions between ions in an electrolyte can be used to produce electricity e.g. in cells and batteries. The reverse can be carried out and electricity can also be used to split ionic substances and is a useful means of producing elements that are too expensive to extract any other way. These topics are dealt with in the electrochemistry sections (see end of energy changes index too).

If you are an Advanced A Level chemistry student, these pages will help as an introduction, but then you should follow the A Level links to the more advanced revision notes and calculation methods - link below. These revision notes on energy transfers in chemical reactions should prove useful for the new AQA chemistry, Edexcel chemistry & OCR chemistry GCSE (9–1, 9-5 & 5-1) science courses.

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