Controlling Reactions Factors that affect Reaction Rates

Rate of a Reaction: The speed at which a chemical reaction proceeds The rate at which a chemical reaction takes place depends on the way the particles of the reactants interact. Chemical reactions do not all occur at the same rate. A particular reaction can be manipulated by changing different factors.

1. Activation Energy: the minimum amount of energy needed to start a chemical reaction All chemical reactions require a certain amount of activation energy to get started. This is the Energy that is needed to break the bonds in the reactants.

2. Catalysts: increase the reaction rate by lowering the required Activation Energy Catalysts are not changed by the chemical reaction Example: Manganese Dioxide (it was present on both sides of the equation) Biological Catalysts are called Enzymes Inhibitors slow down Reactions (ex. preservatives in food)

3. Concentration: the amount of a substance in a given volume Increasing the concentration of reactants supplies the reaction with more particles to react Example: Ice Tea Mix If you add one teaspoon of ice tea mix to your glass it does not taste strong. The more teaspoons you add, the more flavor you taste

4. Surface Area: a measure of the total area that the surface of an object occupies When a solid substance reacts with a liquid or a gas, only the particles on the surface of the solid come into contact with the liquid or gas.

5. Temperature: a measure of the average energy, the random motion, of particles in matter As energy is added to matter in the form of heat, the particles start to move faster and spread out. Faster moving particles will have more energy

Answer these Questions: What is Activation Energy? And why does each reaction need Activation Energy? How does the addition of a Catalyst speed up the reaction rate of that particular reaction? How does the concentration of reactants affect the rate of a chemical reaction?