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Unit 8: Energy changes and reactions of metals

Metals And Their Reactions With Oxygen — HIA International - Grade 7 Revision Notes & Topical Questions

5 min read 8 parts Lesson 5 of 12 1 quiz

📚 HIA International - Grade 7 Hub / Topical Revision
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Lesson summary

8.3 Metals and their reactions with oxygen — HIA INTERNATIONAL notes: Describe how metals react with oxygen and how iron rusts and is protected.Take a small piece of one metal and hold it in tongs.Heat it in a Bunsen flame.Record observations in a table and explain them.Repeat fo…

  • Reactivity
  • Sodium, potassium and calcium
  • Oxide layer
  • Conditions
  • Galvanising
  • Metal oxide

Section 1 of 8Heating metals in air

1
Take a small piece of one metal and hold it in tongs.
2
Heat it in a Bunsen flame.
3
Record observations in a table and explain them.
4
Repeat for each metal.
  • Safety
    • decide precautions first;
      • sodium and potassium are not used because they are too reactive, and gold and silver are not used because they do not react.

Section 2 of 8General reaction

Equation
  • Equation metal + oxygen gives metal oxide.
Oxidation
  • Oxidation this is an oxidation reaction.
Reactivity
  • Reactivity more reactive metals react more quickly; magnesium reacts more quickly than iron.
Magnesium
  • Magnesium burns with a bright white flame to form white magnesium oxide.
Iron
  • Iron burns with sparks as filings and forms iron oxide.
Copper
  • Copper forms black copper oxide when heated.

Section 3 of 8Very reactive and unreactive metals

Sodium, potassium and calcium
  • Sodium, potassium and calcium react without heating, so a cut shiny surface soon dulls.
Storage
  • Storage kept under oil so they do not react.
Oxide layer
  • Oxide layer stops more metal reacting with air or water vapour.
Gold
  • Gold does not react with oxygen and is described as inert.
Silver
  • Silver reacts slowly and goes black as silver oxide.

Section 4 of 8Rusting

Rust
Rust orange-brown iron oxide.
Equation
  • Equation iron + oxygen gives iron oxide.
Conditions
  • Conditions both water and oxygen are needed, although water is not in the equation.
Speed
  • Speed slow, because iron is not very reactive with oxygen.
Harm
  • Harm iron changes and loses its properties, so girders can fall apart.

Section 5 of 8Rusting experiment

TubeConditionsResult
1Open to the air, moist airNail rusted
2Water and airNail very rusty
3Dry air, calcium chloride absorbing waterNo rust
4Boiled water with oil on top, no airA small amount of rust
Fair test
  • Fair test the same type of nail is used in each tube.
Result
  • Result rusting needs water and air.

Section 6 of 8Protecting iron

Painting
  • Painting stops oxygen reaching the iron.
Oiling
  • Oiling also blocks air and water.
Galvanising
  • Galvanising coating the iron with a layer of zinc.

Section 7 of 8Key terms

TermMeaning
OxidationA reaction in which a substance combines with oxygen.
Metal oxideA compound of a metal and oxygen.
InertUnreactive.
RustIron oxide.
GalvanisingCoating iron with zinc.
ReactivityHow readily a substance reacts.
TongsTool for holding hot objects.
TarnishA dull layer formed by reaction with air.

Section 8 of 8Exam technique

1
Saying iron rusts in dry air.
2
Saying all metals burn with a flame — copper just forms a black layer.
3
Saying sodium is stored under water.
4
Saying gold tarnishes quickly.

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