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Kinetics Revision
- 2. Collision Theory What is collision theory? For molecules to react they must first collide In addition, they must be the right orientation … … and have enough energy cv cv
- 3. What affects reaction rate? Temperature Pressure Concentration Particle size Catalyst How fast a chemical reaction goes is affected by many factors. List them … What about enzymes? Enzymes are biological catalysts and for our purposes will be considered the same as chemical catalysts How fast a chemical reaction goes is affected by many factors. List them ...
- 4. Chemical reaction rates Temperature Why does sugar dissolve in tea faster than water? High Temp Molecules have more energy … … fewer collisions Low Temp Molecules have less energy … … fewer collisions
- 5. As surface area increases the rate of reaction generally increases The particles on the surface can react When cut into smaller pieces the particles on the inside can react Chemical reaction rates Surface Area Which one will dissolve first in a cup of tea?
- 6. As the concentration of reactants increases, so does the likelihood that reactant molecules will collide …The fewer red particles in a volume - the less chance of a collision The more red particles in the same volume - there is more chance of a collision Chemical reaction rates Concentration … the rate of reaction increases
- 7. Chemical reaction rates Pressure What happens if you increase the pressure in a reaction? Increase in Pressure Molecules are closer together Number of collisions increases Rate of reaction increases
- 8. A substance that increases the rate of a reaction without being consumed in the reaction Chemical reaction rates Catalysts What is a catalyst? Provide an alternative pathway for reactions … are biological catalysts (proteins) that increase the rate of biochemical reactions Enzymes …
- 9. Chemical reaction rates Look at the picture below … A = B = reactants products Activation energy The energy required for two colliding molecules to react
- 10. Activation Energy Our picture from before can be redrawn … Enthalpy Extent of reaction Activation energy (Ea) enthalpy = energy
- 11. Activation Energy Enthalpy Extent of reaction Ea Energy of reactants Energy of products Because … Energy of reactants Energy of products Exothermic > Energy given out
- 12. Activation Energy Enthalpy Extent of reaction Energy of reactants Energy of productsEa Because … Energy of reactants Energy of products Endothermic > Energy taken in