Year 8 Science Lesson


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Year 8 Science Lesson

  1. 1. Physical and Chemical Change Year 8 Science Ms Alexander
  2. 2. Physical Change ? <ul><li>Definition of a PHYSICAL CHANGE </li></ul><ul><li>A physical change occurs when a a substance changes but no new substance is formed. </li></ul><ul><li>Example of a PHYSICAL CHANGE? </li></ul><ul><li>Melting of ice to water
  3. 3. Chewing my breakfast </li></ul>
  4. 4. Chemical Change ? <ul><li>Definition of a CHEMICAL CHANGE </li></ul><ul><li>A chemical change occurs when a new substance is formed. Another word for Chemical Change is CHEMICAL REACTION. </li></ul><ul><li>Example of a CHEMICAL REACTION? </li></ul><ul><li>Cooking a cake
  5. 5. Burning toast </li></ul>
  6. 6. What are products and reactants?
  7. 7. Chemical Reactions ? <ul>There are 4 types of CHEMICAL REACTIONS <ul><li>Combination
  8. 8. Break-down
  9. 9. Precipitation
  10. 10. Combustion </li></ul></ul>
  11. 11. Last Class <ul><li>What pracs did you do? </li></ul><ul><li>What happened? What was the result? </li></ul>
  12. 12. Combination Reaction ? <ul><li>Definition: A combination reaction occurs when two reactants combine to form a single new substance </li></ul>
  13. 13. Breakdown Reaction ? <ul><li>Definition: A Breakdown reaction occurs where one substance breaks up to a number of smaller ones.
  14. 14. Decomposition in your compost heap!
  15. 15. Start with: Plant material--> C </li></ul>
  16. 16. Precipitation Reaction ? <ul><li>Definition: A reaction were a solid is produced when two solutions are added together. </li></ul>
  17. 17. Combustion Reaction ? <ul><li>Definition: A combustion reaction occurs when a compound reacts with oxygen to produce carbon dioxide and energy.
  18. 18. Example Fireworks, a Bunsen burner, Human respiration </li></ul>
  19. 19. Compare and Contrast ? <ul><li>Create a Venn Diagram. Use the words: products, reactant, synthesis, decomposition
  20. 20. Combination Breakdown Reaction </li></ul>
  21. 21. What might we do to change how quickly a reaction occurs? <ul><li>amount of reactants or concentrations </li></ul><ul><li>Temperature (reactants travel faster) </li></ul><ul><li>surface area (ball with sticks) </li></ul><ul><li>helper chemicals (catalyst) </li></ul>
  22. 22. Rate of Reaction ? <ul><li>A “Rate of Reaction” is the speed at which new products are formed. </li></ul>
  23. 23. On a new page.... ? What effects the rate of a chemical reaction?
  24. 24. Surface area ? <ul><li>A increase of surface area means that there is more rates of contact between reactants
  25. 25. Cut and paste </li></ul>
  26. 26. Temperature ? <ul><li>A increase of temperature means that the reactants can move faster and have more energy to breakdown bonds
  27. 27. What happens if we decrease the energy? </li></ul>
  28. 28. Concentration of reactants ? <ul><li>The more reactants in a reaction the more products are produced.
  29. 29. Cut and paste
  30. 30. What happens if we remove reactants? </li></ul>
  31. 31. Catalysts ? <ul><li>Catalysts are special helper chemicals that assist molecules to react.
  32. 32. But they do not combine with reactants.
  33. 33. Example: Catalytic Converter Movie </li></ul>