Physical and Chemical Changes

40 lessons, pages 321–360.

  1. What Is a Change in Matter? — How substances can alter their form or their identity
  2. Physical Changes — Changes of shape, size and state with no new substance
  3. Chemical Changes — Reactions that make new substances with new properties
  4. Physical or Chemical? Deciding Between Them — The new-substance test and how to apply it
  5. Changes of State as Physical Changes — Melting, boiling, condensing and freezing seen through particles
  6. Dissolving: A Physical Change — Why a dissolved solute is still the same substance
  7. Particles in Physical and Chemical Changes — Rearranging molecules versus rearranging atoms
  8. Conservation of Mass in Changes — Atoms are neither created nor destroyed
  9. Signs of Chemical Change: An Overview — The observable clues that a reaction has happened
  10. Colour Change as Evidence — When a new colour means a new substance, and when it does not
  11. Gas Production and Effervescence — Bubbles from reactions compared with bubbles from boiling
  12. Formation of a Precipitate — Insoluble solids appearing when two solutions mix
  13. Energy Changes: Heat and Light — Temperature changes and light as signs of reaction
  14. Exothermic and Endothermic Changes — Energy released to or taken from the surroundings
  15. Odour and Other Clues — Smell, sound and texture changes, and their limits as evidence
  16. Weighing the Evidence for Chemical Change — Why one sign is rarely enough on its own
  17. Reversible and Irreversible Changes — Can the starting materials be recovered?
  18. Reversing Physical Changes — Evaporation, condensation and freezing to recover substances
  19. Reversible Chemical Reactions — Reactions that can run forwards and backwards
  20. Hydrated and Anhydrous Salts — Blue and white copper(II) sulfate as a reversible change
  21. Thermal Decomposition — Breaking compounds apart with heat
  22. Word Equations for Changes — Writing reactants and products in words
  23. Simple Symbol Equations — Balancing atoms on both sides of an equation
  24. Oxidation: Gaining Oxygen — Metals and other elements combining with oxygen
  25. What Is Rusting? — Iron, water and oxygen forming hydrated iron(III) oxide
  26. Investigating the Conditions for Rusting — Why both water and oxygen are needed
  27. Factors That Speed Up Rusting — Salt, acidic conditions and temperature
  28. Preventing Rust with Barriers — Paint, oil, grease and plastic coatings
  29. Sacrificial Protection and Galvanising — Using more reactive zinc to protect iron
  30. Corrosion of Other Metals — Tarnishing, patina and protective oxide layers
  31. What Is Burning? — Combustion as a rapid reaction with oxygen
  32. The Fire Triangle — Fuel, oxygen and heat, and how removing one stops a fire
  33. Complete Combustion of Fuels — Hydrocarbons burning to carbon dioxide and water
  34. Incomplete Combustion — Carbon monoxide and soot when oxygen is limited
  35. Burning Elements in Oxygen — Oxides of metals and non-metals formed on burning
  36. Candle Flames: Physical and Chemical Changes Together — Melting wax, vaporising and burning in one flame
  37. Fire Safety and Extinguishers — Matching the method to the type of fire
  38. Combustion and the Environment — Carbon dioxide, pollutants and cleaner burning
  39. Changes in Everyday Life — Cooking, baking, weathering and other familiar changes
  40. Physical and Chemical Changes: Unit Review — Bringing together signs of change, reversibility, rusting and burning