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Detailed notes on Metals for Cambridge IGCSE Coordinated Science, covering key concepts, explanations, examples, and exam-focused revision points.
Metals have distinctive physical and chemical properties explained by their giant metallic lattice structure with delocalised electrons. Cambridge tests the structure-property relationship and typical metal reactions.
Mapped to the Cambridge IGCSE 0654 syllabus (2025-2027).
Metals consist of positive ions in a sea of delocalised electrons. This structure explains all their key physical properties.
Metallic bonding: metal atoms release their outer electrons to form a 'sea' of delocalised electrons. The metal consists of a lattice of positive ions (cations) surrounded by and attracted to this electron sea.
Properties and explanations:
| Property | Explanation in terms of metallic bonding |
|---|---|
| Good conductors of electricity | Delocalised electrons are free to move through the lattice; carry charge |
| Good conductors of heat | Delocalised electrons transfer kinetic energy rapidly through the metal |
| Malleable and ductile | Layers of positive ions can slide past each other without breaking bonds (electron sea moves with them) |
| High melting and boiling points | Many strong electrostatic attractions between positive ions and electron sea require much energy to overcome |
| Shiny | Free electrons reflect light |
| Generally solid at room temperature | Strong metallic bonds (except Hg — liquid) |
Metals vs non-metals: Non-metals do NOT have delocalised electrons → poor conductors, brittle (bonds break when layers shift), low MP/BP (simple molecular).
Alloys:
Verbatim phrases and definitions Cambridge mark schemes credit.
Paper 4: 'Explain why metals conduct electricity' (2 marks — delocalised electrons, free to move, carry charge). 'Explain why an alloy is harder than the pure metal' (2 marks — different-sized atoms, disrupt regular layers, cannot slide easily). 'Explain why copper is malleable' (2 marks — layers of ions can slide, electron sea maintains bonding). Structure-property questions are very common.
Sources: Cambridge IGCSE Coordinated Sciences 0654 syllabus 2025-2027 (C10); 0654 Examiner Reports 2022-2024. Last reviewed 2026-05-14.
Step-by-step solutions to past-paper-style questions on properties of metals, written exactly the way a tutor would explain them at the board.
Question
Explain why metals are good conductors of electricity.
Step-by-step solution
Step 1
In metallic bonding, the outer electrons of metal atoms become delocalised — they are no longer associated with specific atoms but are free to move throughout the entire metallic lattice.
Step 2
When a potential difference is applied across the metal, these free (delocalised) electrons move in one direction through the lattice, constituting an electric current.
Step 3
Because electrons can move freely throughout, metals are good conductors of electricity.
Answer
Delocalised electrons free to move throughout the metallic lattice; flow when potential difference applied → electric current → good conductor.
Question
Explain why stainless steel (an alloy of iron, chromium, and nickel) is harder than pure iron.
Step-by-step solution
Step 1
In pure iron, the atoms are arranged in regular layers of the same size. When a force is applied, these layers can slide over each other relatively easily.
Step 2
In stainless steel, chromium and nickel atoms are different sizes from iron atoms. These different-sized atoms are randomly distributed in the iron lattice.
Step 3
The differently sized atoms disrupt the regular layer arrangement, preventing layers from sliding easily over each other.
Step 4
Therefore, stainless steel is harder and less malleable than pure iron.
Answer
Different-sized Cr/Ni atoms disrupt the regular iron lattice; layers cannot slide easily → harder than pure iron.
Examiner tip
Key phrase: 'different-sized atoms disrupt the regular layers'. This is the mechanism for alloy hardness.
Question
Copper is used for household electrical wiring. State TWO properties of copper that make it suitable for this use.
Step-by-step solution
Step 1
Property 1: copper is an excellent conductor of electricity (second only to silver among common metals); low electrical resistance minimises energy loss.
Step 2
Property 2: copper is ductile (can be drawn into long, thin wires without breaking) and flexible, making it easy to install in homes.
Answer
Copper is an excellent electrical conductor AND ductile (can be drawn into wire); also relatively cheap and resistant to corrosion.
Definitions to memorise and the exact keywords mark schemes credit for properties of metals answers — sharpened from recent examiner reports for the 2026 0654 sitting.
Can be beaten or rolled into sheets without breaking; a property of metals due to layers of positive ions that can slide over each other while delocalised electrons maintain bonding.
Can be drawn into wires without breaking; copper and aluminium are particularly ductile, making them useful for electrical wiring.
A mixture of a metal with one or more other elements (metal or non-metal); typically harder and stronger than the pure metal because different-sized atoms disrupt the regular lattice layers.
Example
Steel (Fe + C), brass (Cu + Zn), bronze (Cu + Sn), stainless steel (Fe + Cr + Ni).
Strong electrostatic attraction between a lattice of positive metal ions and a surrounding 'sea' of delocalised electrons; responsible for high melting points, electrical conductivity, and malleability.
The gradual destruction of a metal by chemical reaction with its environment (usually oxygen and water); rusting is the corrosion of iron/steel.
The traps other students keep falling into on properties of metals questions — taken from recent Cambridge IGCSE 0654 examiner reports and mark schemes — and how to avoid them.
Why it happens
Students picture solid bonds snapping under force.
How to avoid it
Layers SLIDE not break; delocalised electrons move with the ions, maintaining the metallic bonding. That's why metals are malleable/ductile, not brittle.
0654 Examiner Report 2023
Why it happens
Students confuse 'less malleable' with 'weaker'.
How to avoid it
Alloys are HARDER and STRONGER than pure metals because the differently sized atoms prevent layer sliding. They are less malleable/ductile, but stronger.
Why it happens
Students know metals have positive ions and make an incorrect inference about charge carriers.
How to avoid it
Electrons (negative charge carriers) are the mobile charge carriers in metals. The positive ions are FIXED in the lattice.
The things students keep getting wrong in this sub-topic, answered.