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Course: Science — Third Preparatory
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Science — Third Preparatory

Science — Third Preparatory

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Science — Third Preparatory 2026/2027

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Unit 1 - Force, Motion, Acceleration and Physical Quantities

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Text lesson

Unit 1 — Chemical Reactions and Their Environmental Impacts

Science — Third Preparatory

Unit 1 — Chemical Reactions and Their Environmental Impacts

1.7 Summary of Lesson 1

1.7 Summary of Lesson 1

Type Pattern Example
Direct combination A + B → AB 2Mg + O₂ → 2MgO
Decomposition AB → A + B 2HgO → 2Hg + O₂
Single replacement A + BC → AC + B Zn + CuSO₄ → ZnSO₄ + Cu
Double replacement AB + CD → AD + CB NaOH + HCl → NaCl + H₂O
  • Key ideas the reactivity series predicts single replacement; neutralisation gives salt and water; precipitation gives an insoluble solid; oxidation is loss of electrons and reduction is gain of electrons; they occur together.
  • Environmental and economic link.
  • Corrosion (for example rusting of iron) is slow oxidation of a metal.
  • Because iron is rather high in the series, it corrodes, and corrosion costs economies enormous sums every year.
  • Using less reactive metals, painting, galvanising (coating iron with zinc) or oiling can save money and resources.
  • This links to responsible consumption.
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