Click to edit Master subtitle style Chapter 4 – Chemical Reactions A Chemical Reaction (a.k.a Chemical Change or Process) involves a change in the composition of the substances involved. One or more starting substances ( Reactants , a.k.a Starting Materials) are converted into one ore more other substances ( Products ). Thus, a chemical reaction involves a rearrangement of atoms in substances, meaning that the way the atoms involved are joined together (bonded) is altered. We describe chemical reactions using Chemical Equations . Reactant formulae are written on the left, and product formulae on the right hand side of a chemical equation, separated by an arrow. Below is the chemical equation describing the combustion of butane (C4H10): Chemical Reactions are accompanied by the release or absorption of heat (see chapter on Thermochemistry), emission of light, formation of a precipitate, release of gas, or color change. The above equation tells us that 2 molecules of butane react with 13 molecules of oxygen gas to give 8 molecules of carbon dioxide and 10 molecules of water. These numbers are called the
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