R2

• a new substances are produced but there is no overall change in mass as there is a fixed relationship between the number of reactant particles and the number of product particles. This is known as the stoichiometry of the reaction.
• an energy change occurs as bonds in the reaction are broken and new onds are formed in the products
• the rate of a chemical reaction is defined as the increase in concentration of one of the products per unit time or as the decrease in the concentration of one of the reactants per unit time.
• collision theory is a method that is used to explain the variation of rate of reaction. A reaction can occur only when two particles collide in the correct orientation and with E>Ea
• activation energy is the minimum energy that colliding particles must have before collision results in a chemical reaction