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Reaction Rates !

Reaction Rates !. February 11 and 12, 2013 Boon Chemistry. Catalyst. Objective I can d efine reaction rate and investigate factors that affect reaction rate. Agenda Catalyst Notes: Reaction Rate Demonstrations: Factors affecting reaction rate Notes: Activation energy and catalysts

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Reaction Rates !

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  1. Reaction Rates ! February 11 and 12, 2013 Boon Chemistry

  2. Catalyst • Objective • I can define reaction rate and investigate factors that affect reaction rate. • Agenda • Catalyst • Notes: Reaction Rate • Demonstrations: Factors affecting reaction rate • Notes: Activation energy and catalysts • Practice/Exit Slip Review your grade report. List at least one strength and one thing you would like to improve. Did you do your homework during the Thermochemistry unit? How much time did you spend studying for the Thermochemistry exam? Did you use your green note sheet on the exam?

  3. Shout Outs! (Period 5) • The following students earned all 3’s and 4’s on the Temperature and Thermochemistry Exam: • Alberto P. , Brayllan R., Alejandro S. • 11% proficient or advanced overall • The following students scored a 3 or 4 on 3 of the four standards: • Ruth B., Carol G., Daijah H., Jeremiah J., Brian M., Jonathan M., Alex P., Pablo R., Raven T., Xochi V. • 48% of students showed at least 75% proficiency

  4. Shout Outs! (Period 3) • The following students earned all 3’s and 4’s on the Temperature and Thermochemistry Exam: • Alejandra A., Irma C., Erik D., Douglas G., DeAndre G., Mario M., Emmanual P., Sandy P., Diana P., Billy V., Andres V. • 39% proficient or advanced overall. • The following students scored a 3 or 4 on 3 of the four standards: • Rosie C., Gerardo G., Perla M., Chris O., Dalia R., Michael V. • 60% of students showed at least 75% proficiency

  5. Shout Outs! (Period 6) • The following students earned all 3’s and 4’s on the Temperature and Thermochemistry Exam: • Melissa A., Karim B., Monique F., Jose G., Jonathan L., Brian M., Kimberly R., Sereno R., Christine R., • 32% proficient or advanced overall. • The following students scored a 3 or 4 on 3 of the four standards: • Kathy A., Daisy B., Kathy C., Kevin C., Clarissa C., Brenda C., Daniel G., Deya G., Sabrina M., Edward S., Alejandro V., Omar V. • 75% of students showed at least 75% proficiency

  6. Shout Outs! (Period 4) • The following students earned all 3’s and 4’s on the Temperature and Thermochemistry Exam: • Walter A., Leslie Al., Richard C., Maria C., Karla G., KiemanG., Michelle G., Patrick J., Abel M., Antonio O., Briceida P., Janet R. • 41% proficient or advanced overall. • The following students scored a 3 or 4 on 3 of the four standards: • Ilsse A., Kevin A., Christina A., Lupe A., Jorge C., Vanessa C., Jessica G., Luis O., Cristina P., Abby R., Edgar S. • 79% of students showed at least 75% proficiency

  7. Shout Outs! (Period 2) • The following students earned all 3’s and 4’s on the Temperature and Thermochemistry Exam: • Jackie A., Susan C., Karen C., Saydy G., Zamir R. • 21% proficient or advanced overall. • The following students scored a 3 or 4 on 3 of the four standards: • Edgardo A., Paola A., Tania C., Erick C., Melody C., Brandell C., Rumaldo G., Rudy M., Denise M., Christian R., Anthony S., Bernabe T., Ivan Z. • 78% of students showed at least 75% proficiency

  8. Start Up: Think Box You will have about 2 minutes to answer on your own. Then you will have about 1 minute to share.

  9. What is Reaction Rate? Rate = change over time • Reaction rate is the rate at which a chemical reaction takes place. • It is measured by the rate of production of productor disappearance of reactant.

  10. What is reaction rate? • A chemical reaction does not have one specific reaction rate. Rather, reaction rateis affected by many different conditions like concentration, temperature, surface areaand pressure. • Usually, the rate decreasesgradually as the reaction continues. The rate is zerowhen the reaction is complete. Video: Reaction Rates vs. Dating -- http://www.youtube.com/watch?v=OttRV5ykP7A Discussion Question: What analogy does the video use to explain the factors that affect reaction rates? What factors affect reaction rates? Can you think of your own analogy?

  11. Demonstration: Affect of Reactant Concentration on Reaction Rate • The demonstration shows the relationship between reactant concentrationand reaction rate. • Summary of Procedure: (1) Two beakers contain aqueous KOH. Beaker 1 has a high concentration and Beaker 2 has a low concentration. (2) Add identical samples of aluminum to both beakers at the same time. (3) Observe the reaction.

  12. Demonstration • The Chemical Reaction: • 2Al(s) + 2KOH(aq) ---> 2K[Al(OH)4] + 3H2 (g) • (a) Labelthereactantsandproducts. (b) Whatreactantconcentrationwillbevaried? (c) Whatgasisproduced? • Hypothesis: How do you think the concentration of KOH will affect the reaction rate? • http://www.youtube.com/watch?v=0StoLU0ZET0

  13. Demonstration: Concentration and reaction rate • Explanation: In order for the reaction to take place, the reactant molecules need to come in contact with each other. The more KOH molecules there are dissolved in the water, the greater the chances that these molecules will collide with the aluminum foil. • Conclusion: As reactant concentration increases, rate increases. As reactant concentration decreases, rate decreases.

  14. Video: Affect of Surface Area on Reaction rate. • The investigation shows the relationship between surface areaand reaction rate. • https://www.youtube.com/watch?v=FJtwkum_QAY • Conclusion:As surface are increases, rate increases. As surface area decreases, rate decreases.

  15. Investigation: Affect of Temperature on Reaction Rate. • The investigation shows the relationship between temperature and reaction rate.

  16. Introduction to Chemiluminescence • In nature, an example of chemiluminescence would be the firefly, which very efficiently creates light through a chemical reaction. Through industrial chemistry we have also created a similar form of emission; however, it is still not as efficient as a firefly. The most common reaction used in novelty toys like glowsticks is that of Cyalume with hydrogen peroxide. Peroxides give off a lot of energy in chemical reactions, and therefore would be perfect for such a precise and efficient reaction.

  17. Introduction to Chemiluminescence • The chemical reaction: • cyalume+ H2O2 + dye → trichlorophenol + 2CO2 + dye[♦]
 In the equation above the diamond [♦] represents the excited stage during which the chemicals give off light. In this investigation, we will study the affect of temperature on the rate of the chemiluminescence reaction.

  18. Investigation • Summary of Procedure: (1) Submerge one light stick in a bath of cold water (about 10°C). (2) Submerge a second light stick in a bath of hot water (about 50°C). (3) Allow each light stick to reach the same temperature as its bath. (4) Remove the light sticks, and activate them. (5) In a dark corner of the room, observe and compare the light intensities of the two sticks. (6) Record your observations. • Hypothesis: How do you think the temperature of the glow stick will affect the reaction rate?

  19. Explanation and Conclusion • Explanation: As temperatureincreases, theproportion of moleculeswithenoughenergytomake a collision lead to a chemicalreactionincreases. Theaffectisnotonlyabouttheincreasednumber of collisions, buttheincreasedenergy of thecollisions. Decreasingthetemperature as theoppositeeffect. • Conclusion: As temperature increases, rate increases. As temperature decreases, rate decreases_.

  20. Using Balanced Chemical Equations to Express Reaction Rates. • The reaction rate can be measured as the rate of appearance of a product or the rate of disappearance of a reactant. This means that there is more than one way to express the reaction rate of any chemical reaction. The rate expression must show the stoichiometric relationship between the reactants and products. So, the rate expression includes coefficients from the balanced chemical equation.

  21. Example: The combustion of propane: • C3H8+ 5O2è 3CO2 + 4H2O rate = -Δ[C3H8] = -Δ[O2] = Δ[CO2] = Δ[H2O] Δt 5Δt3Δt 4Δt

  22. Homework • Read pp. 586-595. Pay particular attention to information about activation energy and catalysts. • Problems pp. 595 #3, 4, 5, 9, 11, 14

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