1. KINETICS Kinetics is the study of change in a system. In this section we will look at what factors affect how FAST a reaction will occur. How fast does a newspaper burn? How fast does a steel beam burn? These are kinetics.

2. Kinetics Before we can learn about what affects a reaction, we need to look for a minute at how a reaction happens. There are several new terms here so we will start off with a few definitions.

3. Definitions COLLISION THEORY the theory that describes HOW a reaction happens RATE OF REACTION how fast a reaction happens ACTIVATION ENERGY The energy needed to get a reaction started.

4. Definitions Exothermic Reactions The overall reaction will release energy to the outside Most reactions are exothermic. The reaction will produce “heat” Endothermic Reactions The overall reaction will consume energy Few reactions are endothermic The reaction will appear to get cold.

5. Collision Theory Collision Theory says that for a reaction to happen, three things must occur: 1)The reactants must come into physical contact with each other--the atoms or molecules must bump into one another 2)The atoms or molecules must have sufficient energy to initiate the reaction 3)The molecules must hit one another with the proper orientation.

6. Analogy Time We wish to lock bumpers between our 1952 Pick Up Truck and that cute little Mercedes Benz over on the other side of the parking lot. Before we can lock bumpers we must-physically hit the Mercedes with our truck, we must hit with enough energy to force the bumpers together and we must actually hit each other bumper to bumper.

7. 1) contact2) energy 3) orientation If we hit the Mercedes going 1 mph we probably will not lock bumpers. (#2) If we hit the side of the car we probably will not lock bumpers (#3) if we hit the Mercedes going 175 mph we will probably not lock bumpers (#2) (or be able to find bumpers either). If we sit on the other side of the parking lot and watch we will probably not lock bumpers (#1).

8. Back to Reality When we look at what factors affect reaction rates, then we will look at what factors affect the three parts of a reaction and in what manner they are affected.

9. Activation Energy Before we continue our stroll through the parking lot of kinetics, we need to look at one more term. That term is called activation energy. Activation energy is the energy necessary to get a reaction started.

10. Activation Energy Let’s think of a graph in which the Y axis is the energy within a system. The X axis will show the reactants on the left and the products on the right. We will draw a line from the reactants to the products representing what happens to the total energy during the course of the reaction.

11. Reaction Rates We will look at four different factors that affect reaction rate and how they work. These factors are: a)identity of reactants b)concentration of reactants c)temperature d)catalyst

12. 1) contact2) energy 3) orientation a)Identity of Reactants This is important because of the individual energy levels of the reactants and the energy in the resulting products. This affects item #2 above. Think about the bullies--they have lots of extra energy and react VERY easily.

13. Analogy If you wish to see a good understanding of this concept that reactants make a difference do this simple little test. Go up to one bully and one weenie in the lunch room Lick their chocolate chip cookie. Which one reacts faster--the bully or the weenie?

14. 1) contact2) energy 3) orientation b)Concentration of reactants This particular item impacts #1 above. The higher the concentration the more likely the reactants will bump into each other.

15. Analogy, Continued To illustrate this concept, we will return to the lunch room Instead of licking the cookie on one bully’s plate, Lick the cookie on 12 bully’s plates. The reaction will proceed with even greater vigor.

16. 1) contact2) energy 3) orientation c)Temperature Temperature affects #2 above. The top of our activation energy graph, point b, stays the same. If we increase the energy of the reactants, we have decreased the a-b distance and lowered the activation energy thus allowing the reaction to happen easier.

17. Analogy continued You have just managed to get the 12 meanest people in school mad at you. Your mission, should you decide to accept it, will be to get away before these bullies get too HOT under the collar. You will self destruct during the next recess.

18. 1) contact2) energy 3) orientation d)Catalyst A catalyst is like a match maker. The catalyst grabs hold of reactant “A” and says You looking for “B”. And then the catalyst grabs “B” and says You looking for “A” Here meet.

19. Analogy, concluded To make matters worse, at the next recess the 5 foot 1 inch, 87 pound, 140 year old great grandmother, play-ground monitor tells the bullies that they should not bother you or they will have to deal with HER! Yeah right.

20. 1) contact2) energy 3) orientation d)Catalyst, continued So a catalyst helps bring chemicals together more efficiently (#1 above) and with the proper orientation (#3) above.

21. Reaction Rates Reaction Rates are measured in terms of changes in concentration as a function of time. Kind of like changes in distance as a function of time--miles per hour. The faster the rate, the faster the reaction. The faster the rate, the shorter the time it takes for a reaction to be completed.

22. Reaction Rates Analogy Our rate from Twin Falls to Boise is 25 mph. The travel time will be about 5 hours. Our rate from Twin Falls to Boise is 60 mph. The travel time will be about 2 hours.

23. Reaction Rates Analogy Continued Our rate from Twin Falls to Boise is 120 mph. The travel time will be 4 days 3 hours with most of that time spent in the Mountain Home Jail.

24. Reaction Rates In order to measure reaction rate, we measure how long it takes a reaction to happen. Reaction rate is then 1/time. If the reaction happens in 30 minutes, the rate would be 1/30 = 0.033 min -1

25. Reaction Rates In order to measure reaction rate, we measure how long it takes a reaction to happen. Reaction rate is then 1/time. If the reaction happens in 300 minutes, the rate would be 1/300 = 0.0033 min -1

26. Reaction Rates The faster the rate, the shorter the time. The slower the rate, the longer the time. Time and rate are inverses of each other.

27. Reaction Rates If you want to grow up and be a chemist and make money doing chemical reactions, You want the reactions to happen as quickly as possible and still be safe. That makes the most money in the shortest amount of time without blowing up your plant and your employees.