Ch. 19 Reaction Rates and Equilibrium

Section 19.1 Reactions can occur: Very Fast- like a firecracker Very Slow- turning a dead plant into coal Moderately- Food spoiling Reaction rate – is the speed of change in a reaction within any interval of time.

Collision Theory: reactions occur when atoms, ions, or molecules collide to form products. Particles must have enough Kinetic Energy (movement). Molecules much touch (or collide) to react Only a small fraction of collisions produce a reactions because some particles lack the kinetic energy to react. When the molecules don’t have the kinetic energy to react, they bounce off each other unchanged

Activation Energy- minimum amount of energy particles must have to react. Activation Complex (Transition State)- moment when reactants change into products

Factors Affecting Reaction Rates Temperature Increase temperature speeds up reactions because particles are moving around faster ( ↑KE) Decrease temperature slows down reactions because particles slow down (↓KE) Concentration More particles = more collisions

Factors Affecting Reaction Rate Particle Size Increase surface area = more exposure and collisions Therefore, reaction rate is increased. Grinding into smaller pieces increases surface area. Catalyst Substance that helps a reaction get started or move along faster Catalysts are not used up or part of the reaction Written above arrow in reactions

Ex: Inhibitor (opposite of a catalyst): interferes with action of a catalyst aka: blocker