Chemical Reactions & Equations
A chemical reaction leads to the transformation of one set of substances into another set of new substances and transfer of energy takes place. A chemical reaction is occurring or has occurred if it is accompanied by one or more of the following characteristics that are evolution of gas, change of colour, formation of precipitate, change of state and change of smell. Chemical reactions are also accompanied by energy change. Two types of chemical reactions are seen depending on the energy change, exothermic reaction and endothermic reaction. Chemical reactions in which heat is released or evolved are called exothermic reactions. Chemical reactions in which heat is absorbed are called endothermic reactions. A chemical reaction is represented by a chemical equation. A chemical equation is the symbolic representation of a chemical reaction using symbols and formulae of the substance involved. Equation in which reactants and products are represented by their names is known as word equation.