2. 4.11 Vocabulary - 10/8/07 Reaction rate: The speed at which reactants form products. Reactions rates can be modified. Temperature: The average kinetic energy of particles. Concentration: The amount of a specified substance in a unit amount of another substance. Surface area: A measure of the exposed area Catalyst: A substance added to the reactants that increases the rate of a reaction without being consumed in the process. Particle collisions: an interaction between particles which causes an energy transfer.

3. Catalysts & Reaction Rates PS-4.11 Explain the effects of temperature, concentration, surface area, and the presence of a catalyst on reaction rates.

4. Chemical Reactions Occur when reactants collide! Reactants must collide with sufficient energy to react! It is important to consider particle collisions when looking at reactions!

5. What factors affect the rate of a reaction? Reaction rate factors include: Temperature Concentration Surface area Catalysts

6. Temperature When temperature increases, the rate of a chemical reaction increases. Higher temp  More collisions!

7. Concentration When reactants are concentrated, the rate of a chemical reaction will increase. Better odds of collision if concentrated!

8. Surface Area When the surface area of reactants increases, the reaction rate increases. Better odds of collisions with smaller particle size!

9. Catalysts The presence of a catalyst will speed up a chemical reaction by lowering the amount of energy needed to start a reaction

10. Catalysts Catalysts remain unchanged in a reaction and do not change amount of product, they only change the rate of production!

11. Elephant toothpaste Write out this formula & balance it: Dihydrogendioxide breaks down into water & oxygen gas 2H2O2  2H2O + O2(g) What kid of equation is this? Decomposition

12. Elephant toothpaste 2H2O2  2H2O + O2(g) Think about when you get a cut & use hydrogen peroxide…. It bubbles up. That bubbly gas is oxygen. Hydrogen Peroxide isn’t very stable, so it is constantly breaking down. It’s always decomposing to water and oxygen Under normal conditions, the decomposition goes very slowly.

13. Elephant toothpaste 2H2O2  2H2O + O2(g) Do you want to see it speed up???? Add yeast, it catalyzes the decomposition, making the reaction go much more quickly. Add a dish soap, the oxygen gas gets stuck in the soap making it bubbly Add food coloring….you get colored elephant toothpaste!

14. REVIEW What is the average kinetic energy of particles called? Temperature What is the amount of exposed area called? Surface area What is the amount of a specified substance in a unit amount of another substance? Concentration

15. REVIEW What is speed at which reactants turn into products called? Reaction Rate What is an interaction between particles which causes an energy transfer? Particle collisions What do you call a substance that you add to the reactants that increases the rate of a reaction? Catalyst

16. REVIEW True or False: Catalysts are consumed by the chemical reaction. False What is the effect of increased temperature on a chemical reaction? It speeds up! What is the effect of concentration on a chemical reaction? It speeds up!

17. REVIEW What is the effect of increased temperature on a chemical reaction? It speeds up! What is the effect of a smaller surface area on a chemical reaction? It speeds up! Chemical reactions only occur when there is enough ___________. Energy!