Chemical Reactions and Properties of Metals

Reactions with Metals

• Metals react with oxygen to form metal oxides.
• Metal oxides are basic and form bases.
• Magnesium + oxygen → magnesium oxide is an example.
• Group 1 metals react rapidly with water, forming soluble hydroxides (alkalis) and hydrogen gas.
• Other metals are less reactive; transition metals react only with steam, not water.

Properties of Metals

• Good conductors of electricity.
• Good conductors of heat.
• Shiny (lustrous).
• High density (heavy for their size).
• Malleable (can be hammered into different shapes).
• Ductile (can be pulled into wires).
• Sonorous (make a ringing sound when hit).

Properties of Non-Metals

• Poor conductors of electricity (except graphite).
• Poor conductors of heat (except graphite).
• Dull.
• Low density (light for their size).
• Brittle (break when hammered or pulled).
• Not sonorous (make a dull sound when hit).

Writing Balanced Symbol Equations with State Symbols

• (s) means solid.
• (g) means gas.
• (l) means liquid.
• (aq) means aqueous solution.
• Example: 2Mg(s) + O2(g) → 2MgO(s)
• Example: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)

Tests for Gases

Rusting

• Chemicals in the air attack metals, causing the surface to be eaten away (corrosion).
• The corrosion of iron and steel is called rusting.
• For rusting to occur, both oxygen and water are needed.
• Rusting is sped up by electrolytes such as salt.
• Rust is weak, so it flakes away, exposing fresh metal to rust.

Stopping Rust

• Methods to prevent rusting include:
  • Painting
  • Coating with plastic.
  • Greasing and oiling.
  • Metal plating (e.g., chromium or tin).
  • Galvanizing (coating with zinc).

Galvanizing

• Coating iron with zinc.
• Stops oxygen and water from reaching the iron.
• Zinc reacts with water, protecting the underlying iron (sacrificial protection).

The Reactivity Series

• A list of metals in order of their reactivity to water, oxygen, and hydrochloric acid.
• Reactivity (increasing): Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Tin, Lead, Hydrogen, Copper, Silver, Gold, Platinum .
• Elements below hydrogen do not react with cold water, steam, or hydrochloric acid.
• The more reactive a metal, the more difficult it is to extract from its ore and the more stable its compounds.

Metals at the Bottom of the Reactivity Series (Below Hydrogen)

• Unreactive (e.g., gold, silver, platinum).
• Exist as elements in the Earth's crust (native metals).
• Easily separated from other substances.

Metals in the Middle of the Reactivity Series (Between Hydrogen and Carbon)

• Exist as oxides.
• Carbon used to extract them (carbon reacts with the oxygen in the oxides forming carbon dioxide).
• Carbon is more reactive than the metals, so it displaces the metal from its compound.

Metals at the Top of the Reactivity Series (Above Carbon)

• Highly reactive (e.g., aluminum, sodium).
• Difficult to extract from their compounds.
• Extraction by electrolysis.

Metal Reactions with Water or Steam

• Metals exhibit varying reactivities with water or steam.
• Potassium and sodium react violently.
• Others, such as iron, react slowly.
• Copper & Silver do not react.

Comparing Metal Reactions with Acids and Oxygen

Tables provide relative reactions between various metals and dilute acid; compared with reactions with oxygen.

Displacement Reactions

• If metal X is more reactive than metal Y, it displaces Y in a compound.
• Example: Iron + copper sulphate → iron sulphate + copper.

Oxides in Displacement Reactions

• Some oxides can also be displaced by more reactive metals.
• Extracting metals from their ores involves displacing metals from their oxides.
• Aluminum + iron oxide → aluminum oxide + iron. (Thermite reaction)
• Example of displacement:Iron can displace copper from copper oxide.

Extracting Metals

• Most metals exist as compounds (in ores).
• Method of extraction depends on the metal's reactivity.
• The higher up a metal is in the reactivity series, the more difficult it is to extract.