Reaction Rates reaction rate: a measure of how fast reactions happen – based on collisions of atoms and molecules ex. explosive and biological reactions are very fast and iron rusting is very slow. Reaction rate is measured by the rate of decrease in concentration of reactants or as the rate of increase in concentration of the products 6 CO2 + 6 H2O  C6H12O6 + 6 O2

Reaction Rates Concentration, temperature, surface area, and pressure are major factors Increasing the concentration of reactants increases the number of collisions Ex. More oxygen  better burning

Reaction Rates Increasing temperature increases the number of collisions  greater kinetic energy increases the chances of each collision leading to a reaction Ex. Food spoils slower and glow sticks last longer in fridge Increasing pressure increases the reaction rate only when one or more of the reactants or products are gases. With gaseous reactants, increasing pressure is the same as increasing concentration  increased reaction rate

Reaction Rates Increasing surface area increases the number of collisions  increased reaction rate -as such, smaller particles increase reaction rate

Reaction Rate Scenarios Write down whether the following will increase or decrease a reaction rate and explain why. 1. Lowering the temperature of reactants. 2. Diluting an aqueous solution of HCl with water before adding a piece of magnesium. 3. Grinding a solid into fine particles. 4. Increasing the pressure of a mixture of gases.