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Unit 5: Reactivity

Chemical properties of metals — HIA International - Grade 8 Revision Notes & Topical Questions

5 min read 8 parts Lesson 6 of 12 2 quizzes

📚 HIA International - Grade 8 Hub / Topical Revision
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Lesson summary

Chemical properties of metals — HIA INTERNATIONAL notes: Describe the reactions of metals with oxygen, water and acids and use them to order metals by reactivity.Chemical property = how a substance reacts, e.g.

  • Physical properties
  • Faster reaction
  • Very reactive metals
  • Oxide layer
  • Inert metals
  • Conditions

Part 1 of 6Chemical and physical properties

Chemical property
Chemical property how a substance reacts, e.g. with oxygen, water or acid.
Physical properties
  • Physical properties such as shiny and conducting involve no new substance.
Reactivity
  • Reactivity comparing reactions shows which metals are more reactive than others.

Part 2 of 6Reaction with oxygen

Equation
  • Equation metal + oxygen → metal oxide; this is an oxidation reaction.
Heating
  • Heating many metals react if they get hot enough; magnesium burns with a bright white flame.
Faster reaction
  • Faster reaction magnesium reacts more quickly than iron, so it is more reactive.
Very reactive metals
  • Very reactive metals sodium, potassium and calcium tarnish in air without heating, so they are stored under oil.
Oxide layer
  • Oxide layer a layer of oxide on the surface stops any more of the metal reacting.
Silver
  • Silver reacts slowly with air and goes black as silver oxide forms.
Inert metals
  • Inert metals gold does not react with oxygen.

Part 3 of 6Rusting of iron

Rust
Rust iron oxide, an orange-brown solid formed by iron + oxygen → iron oxide.
Conditions
  • Conditions both water and oxygen must be present, and it happens slowly.
Evidence
  • Evidence nails rust in moist air and in water and air, and not in dry air.
Damage
  • Damage a rusted girder can fall apart and a building could collapse.
Protection
  • Protection paint stops oxygen reaching the iron; galvanising covers it with zinc.

Part 4 of 6Reaction with water

Equation
  • Equation metal + water → metal hydroxide + hydrogen.
Sodium and potassium
  • Sodium and potassium react very vigorously;
    • potassium produces enough thermal energy for the hydrogen to catch fire;
    • stored under oil.
Calcium and magnesium
  • Calcium and magnesium react less vigorously, with calcium reacting with cold water.
Steam
  • Steam metal + steam → metal oxide + hydrogen, e.g. magnesium + steam → magnesium oxide + hydrogen.
No reaction
  • No reaction gold and other unreactive metals do not react with water.
Preparation
  • Preparation clean the metal with sandpaper to remove the oxide layer.

Part 5 of 6Reaction with acids

Equation
  • Equation metal + acid → salt + hydrogen, e.g. zinc + hydrochloric acid → zinc chloride + hydrogen.
Hydrogen test
  • Hydrogen test a lighted splint gives a squeaky pop.
Unreactive metals
  • Unreactive metals copper, silver and gold do not react with dilute acids.

Part 6 of 6Order of reactivity

MetalOxygenWaterDilute acid
Potassium, sodiumReact quickly without heatingVigorousViolent
CalciumBurns brightly when heatedSlow reaction in cold waterVigorous
MagnesiumBurns brightly when heatedReacts with steamFast
Zinc, ironSlow when heatedReacts with steam, not waterSteady to slow
CopperSlowNo reactionNo reaction
Silver, goldLittle or noneNo reactionNo reaction
Displacement
  • Displacement a more reactive metal displaces a less reactive one from a compound.
Example
  • Example iron + copper sulfate → iron sulfate + copper.

Key terms

TermMeaning
OxidationA reaction in which a substance combines with oxygen.
InertNot reacting.
RustIron oxide formed by iron reacting with oxygen and water.
GalvanisingCoating iron with zinc to prevent rusting.
Metal hydroxideThe compound formed when a metal reacts with water.
Reactivity seriesA list of metals ordered by how readily they react.
DisplacementA more reactive metal taking the place of a less reactive one.

Avoid these mistakes

1
Metals only react when heated — very reactive metals react with air without heating.
2
Rust needs only oxygen — iron needs both water and oxygen.
3
Sodium is safe to test in water — it reacts violently and is stored under oil.
4
Copper reacts with dilute acid — it is below hydrogen in the series and does not.

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