Chemistry: A Volatile History Chemistry: A Volatile History Chemistry: A Volatile History is a 2010 BBC documentary on the history of chemistry presented by Jim Al-Khalili. It was nominated for the 2010 British Academy Television Awards in the category Specialist Factual. Only in the last 200 years have we known what an element is – a substance that cannot be broken down further by chemical reaction. The Ancient Greeks, with no way of breaking open substances, could only base their ideas of the elements on what they could see: Earth, Fire, Water and Air. In the 16th century alchemists were busy trying to turn
Defining equation (physical chemistry) Defining equation (physical chemistry) In physical chemistry, there are numerous quantities associated with chemical compounds and reactions; notably in terms of "amounts" of substance, "activity" or "concentration" of a substance, and the "rate" of reaction. This article uses SI units. Theoretical chemistry requires quantities from core physics, such as time, volume, temperature, and pressure. But the highly quantitative nature of physical chemistry, in a more specialized way than core physics, uses molar amounts of substance rather than simply counting numbers; this leads to the specialized definitions in this article. Core physics itself rarely uses the mole, except in areas overlapping