Properties of Metals Notes

Cambridge IGCSE Chemistry: Revision notes

Key facts

  • Metals conduct heat and electricity, are malleable and ductile, shiny, dense and mostly have high melting points (mercury is an exception).
  • These properties come from delocalised electrons.
  • Metal + dilute acid → salt + hydrogen (squeaky pop test).
  • Metal + oxygen → metal oxide.
  • Metals react with water or steam to give a hydroxide or oxide, and hydrogen.
  • Reactivity: Na > Ca > Mg > Zn > Fe > Cu.

Physical properties

Metals conduct well, can be shaped without breaking and are generally shiny and dense.

Metals are malleable (hammered or rolled into sheets) and ductile (drawn into wires). These properties arise from the delocalised electrons, which move freely and carry heat and charge. Atoms can slide past each other without breaking the metallic bonding. Non-metals lack delocalised electrons and are brittle.

Metals

Thermal conductivity:
Good conductors
Electrical conductivity:
Good conductors
Malleable and ductile:
Yes: can be hammered or drawn into wires
Melting and boiling points:
Mostly high (except mercury)
Appearance:
Shiny and lustrous
Density:
Generally high

Non-metals

Thermal conductivity:
Poor (insulators)
Electrical conductivity:
Poor (insulators)
Malleable and ductile:
Brittle: shatter when hammered
Melting and boiling points:
Mostly low
Appearance:
Dull
Density:
Generally lower

Why do metals conduct electricity?

Metals and dilute acids

Reactive metals give a salt and hydrogen; the more reactive the metal, the more vigorous the reaction.

Metal + dilute acid → metal salt + hydrogen. Magnesium is vigorous (Mg+2 HCl→MgClX2+HX2\ce{Mg + 2HCl -> MgCl2 + H2}), zinc is moderate (Zn+2 HCl→ZnClX2+HX2\ce{Zn + 2HCl -> ZnCl2 + H2}), iron is slow (Fe+HX2SOX4→FeSOX4+HX2\ce{Fe + H2SO4 -> FeSO4 + H2}), copper does not react. Signs: fizzing, warm solution, the metal disappearing. A lighted splint gives a squeaky pop.

Magnesium

  • Vigorous

Zinc

  • Moderate, steady fizzing

Iron

  • Slow

Copper

  • No reaction

Worked example

Write the word and symbol equation for zinc with hydrochloric acid, and say how to test the gas.

Which metal does not react with dilute acid?

Metals and oxygen

Metals heated in oxygen form metal oxides, with more reactive metals reacting more vigorously.

Metal + oxygen → metal oxide (combustion). Order of reactivity: Na > Mg > Fe > Cu. Signs: burning or glowing, a coloured flame, a solid oxide, heat and light.

Sodium

  • Burns with a yellow flame: 4 Na+OX2→2 NaX2O\ce{4Na + O2 -> 2Na2O}

Magnesium

  • Intense bright white flame: 2 Mg+OX2→2 MgO\ce{2Mg + O2 -> 2MgO}

Iron

  • Burns with sparks, grey-black solid: 3 Fe+2 OX2→FeX3OX4\ce{3Fe + 2O2 -> Fe3O4}

Copper

  • Turns black when heated: 2 Cu+OX2→2 CuO\ce{2Cu + O2 -> 2CuO}

What colour is the flame when magnesium burns?

Metals, water and steam

More reactive metals react with cold water to give a hydroxide and hydrogen; less reactive ones need steam.

With cold water: sodium is vigorous (2 Na+2 HX2O→2 NaOH+HX2\ce{2Na + 2H2O -> 2NaOH + H2}); calcium is moderate (Ca+2 HX2O→Ca(OH)X2+HX2\ce{Ca + 2H2O -> Ca(OH)2 + H2}); magnesium is very slow. With steam: magnesium reacts vigorously to give white magnesium oxide (Mg+HX2O(g)→MgO+HX2\ce{Mg + H2O(g) -> MgO + H2}) and iron reacts with red-hot steam (3 Fe+4 HX2O(g)→FeX3OX4+4 HX2\ce{3Fe + 4H2O(g) -> Fe3O4 + 4H2}). Copper does not react.

Cold water

Sodium:
Vigorous
Calcium:
Moderate
Magnesium:
Very slow
Iron:
No reaction

Steam

Sodium:
Not needed
Calcium:
Not needed
Magnesium:
Vigorous
Iron:
Reacts

Which metal reacts vigorously with cold water?

Try an exam question

Describe what you would see when magnesium is added to dilute hydrochloric acid, and how you would test the gas produced.

[4 marks]

That's the notes covered.

Carry on to the next subtopic.