Unit 7: Reaction EnergySECTION 1: REACTION RATE

Energy in Reactions

• In order for a reaction to occur, energy MUST be involved.

• Reactions that release (give off) energy are called exothermic reactions

• Reactions that absorb (take in) energy are called endothermic reactions

•This energy absorbed or released is beyond the activation energy – energy required to cause a reaction to occur

Exothermic vs. Endothermic Reaction

Curves

Reaction Rate

•The rate at which reactants change into products over time

•Relates to how fast the reaction is occurring

Factors Affecting Reaction Rate

• Temperature: –Generally, as

you increase temperature, you increase the rate of the reaction

–As you heat a substance, the molecules move around faster• They collide and

react more!

Factors Affecting Reaction Rate

•Surface Area:–The surface of a substance is the area that will react with its surroundings

–An increase in the surface area results in an increase in the amount of exposure the substance has to the surroundings

–Increased surface area increases reaction rate

Factors Affecting Reaction Rate

•Concentration:

–Refers to the number of particles of a substance in a given area

–The more particles present, the higher the concentration and therefore, the quicker a reaction will occur

Factors Affecting Reaction Rate

Temperature

Surface Area

Concentration

Increase in

Reaction Rate

Factors Affecting Reaction Rate

•Catalysts:–Substance that

affects the reaction rate without being used up in the process

– Instead of affecting the particles that are reacting, a catalyst DECREASES the activation energy of a reaction; therefore, making the reaction occur more easily!