Ms. Samayoa Birmingham community charter high school Chemistry Kinetics Ms. Samayoa Birmingham community charter high school Chemistry

Learning Objective: Students will understand the underlying factors that affect chemical reaction rates by creating a school dance analogy. Academic Vocabulary: kinetics, rate of a reaction, Collision Theory, activation energy, and catalyst

Introduction Kinetics is the study of rates and mechanisms of chemical reactions Rate is the speed at which a reaction is taking place A mechanism is a series of reactions that lead to final products of a reaction

Collision Theory According to Collision Theory, chemical reactions occur because reactants are constantly moving around and colliding with one another

Effective Collision Effective collisions occur when reacting particles collide with sufficient (right amount of) kinetic energy at proper orientation (angle)

Rate of a Reaction Rate of a reaction depends on frequency of (how often) effective collisions occur between particles Any factor that can change the frequency of effective collisions between reacting particles will change the rate of that reaction

How do we change the speed of a reaction?

Concentration and Reaction Rate Increasing concentration increases rate of a reaction because there will be more particles to collide, and the frequency of effective collisions will increase Decreasing concentration decreases the rate of a reaction because there will be fewer particles to collide, and the frequency of effective collisions will decrease

Concentration and Reaction Rate More H2 gas is produced when magnesium (Mg) is placed in acidic solution of a higher concentration (4M) than in acidic solution of lower concentration (2M)

Temperature and Reaction Rate Increasing temperature of reacting solutions increases rate because energy of particles increase, resulting in an increase in the frequency of effective collisions Decreasing temperature of reacting solutions decreases rate because energy of particles will decreases, resulting in a decrease in the frequency of effective collisions

Pressure and Reaction Rate Increasing pressure on a reaction that involves gases increases the reaction rate because the concentrations of the reactants will increase due to a decrease in the volume of the system Decreasing pressure on a reaction that involves gases decreases the reaction rate because the concentrations of the reactants will decrease due to an increase in the volume of the system At a higher pressure of 2 atm, the volume of the reaction is decreased, resulting in greater concentration of reactants Therefore, reaction at the higher pressure will be faster

Surface Area and Reaction Rate Surface area is the amount of exposed area of a set of mass of a solid substance Increasing surface area of a solid increases reaction rate because there will be more exposed areas for effective collisions to occur Decreasing surface area of a solid decreases reaction rate because there will be fewer exposed areas for effective collisions to occur

Activation Energy and Catalysts Activation energy is the energy needed to start a chemical reaction. ALL chemical reactions require some amount of activation energy Chemical reactions that require low activation energy are faster than those that require high activation energy

Activation Energy

Activation Energy and Catalysts A catalyst is a substance that can increase the speed (rate) of a reaction by lowering the activation energy A catalyst in a reaction provides an alternate (lower activation energy) pathway for a reaction to occur faster

Catalyst