Chapter 4.4

*Energy and Rates of Chemical Reactions

*Reactions and Energy

*Energy is needed to break bonds

*Law Conservation of Energy- Energy cannot be created or destroyed.

*It can change forms

*Exothermic Reaction

*Exo means “exit”

*Thermic means “Heat” or “Energy”

*Define Exothermic

*How does an exothermic reaction feel?

*Endothermic Reaction

*Endo means “go in”

*Thermic means “heat” or “energy”

*Define Endothermic

*How does an endothermic reaction feel?

*Rates of Reactions

*Activation Energy: Smallest amount of energy that is required for molecules to react

*Striking a match

*Friction is a source of activation energy

*Catalyst

*Catalyst- speeds up a reaction by lowering the amount of energy needed so that a reaction can happen more easily. *Are not actually part of the products or reactants.

Enzymes in the body are catalysts too!

*Inhibitor

*Inhibitor- slows down a reaction

*Factors Affecting Rates of Reactions

Temperature

*At high temperatures, particles of reactants move quickly.

*The higher the temperature……

*Factors Affecting Rates of Reactions

Concentration

*A measure of the amount of one substance dissolved in another substance.

*There is a small distance between particles with a high concentration

*The higher the concentration……

*Factors Affecting Rates of Reactions

Surface Area

*The amount of exposed surface of a substance

*Grinding a solid into a powder makes a larger surface area

*The greater the surface area……

*Factors Affecting Rates of Reactions

Inhibitor vs. Catalysts

*Inhibitor: substance that slows down or stops a reaction.

*Preservatives

*Catalyst: substance that speeds up a reaction without being permanently being changed

*Not a reactant

*Enzymes

*Catalytic Converter