Metals & Non-Metals – Complete Study Notes

Physical Properties of Metals and Non-Metals

• State at room temperature
• All metals are solid at room temperature except mercury.
• All non-metals are either gases or brittle solids at room temperature; bromine is the only liquid non-metal.

• Lustre
• Metals possess metallic lustre (shiny).
• Non-metals generally lack lustre; exceptions that shine: diamond and iodine.

• Hardness
• Metals are generally hard; diamond (a non-metal) is the hardest naturally-occurring substance.
• Sodium and potassium are so soft they can be cut with a knife.

• Malleability (can be beaten into sheets)
• Excellent in metals such as gold, silver, aluminium; absent in non-metals.
• Definition often asked: Some metals can be beaten into thin sheets without breaking.

• Ductility (can be drawn into wires)
• High for gold, silver, copper, aluminium.
• Non-metals are non-ductile; you cannot draw a wire out of wood.

• Sonorous nature
• Metals produce ringing sound when struck ⇒ used in bells & gongs.

• Electrical & thermal conductivity
• Metals: good conductors; copper is best for both heat and electricity (silver is better but costlier).
• Non-metals: poor conductors; graphite is the only good electrical conductor among them.

• Melting / boiling points
• Metals generally have high melting points; non-metals low.
• Exact statement from text: Melting point of most of the metals is higher than that of non-metals.

• Density & tensile strength
• Metals usually have high density and tensile strength (iron suitable for bridges, houses etc.).

Chemical Properties

• Reaction with oxygen / air
• Metals form basic oxides (e.g., $4Na + O<em>2 \rightarrow 2Na</em>2O$).
• Non-metals form acidic / neutral oxides; carbon forms acidic oxide $CO_2$ on combustion.
• Aluminium instantly forms a thin, protective oxide layer that prevents further corrosion.

• Reaction with water
• Highly reactive metals (K, Na) react violently and exothermically:
$2K + 2H<em>2O \longrightarrow 2KOH + H</em>2\uparrow$
$2Na + 2H<em>2O \longrightarrow 2NaOH + H</em>2\uparrow$
• Magnesium reacts slowly with cold water but quickly with steam.
• Metals like Cu, Ag, Au show no reaction with water.

• Reaction with dilute acids
• Many metals liberate hydrogen: $Zn + H<em>2SO</em>4 \rightarrow ZnSO<em>4 + H</em>2\uparrow$.
• Noble metals (Cu, Ag, Au, Pt) do not liberate $H_2$.
• Text reminder: Not all metals evolve hydrogen gas with dilute acids.

• Reactivity toward air, water & acids
• Order (decreasing reactivity) – complete series mentioned in class: K > Na > Ca > Mg > Al > Zn > Fe > Sn > Pb > (H) > Cu > Hg > Ag > Pt > Au.
• Gold lies at the bottom of the reactivity series, hence remains un-attacked by air, water and most acids.

Corrosion & Rusting

• Definition
• Corrosion: Destruction of a metal due to action of oxygen and moisture in air.
• Rusting is corrosion of iron forming red-brown $Fe<em>2O</em>3·xH_2O$; requires both air (oxygen) and water.

• Prevention methods
• Painting / varnishing
• Greasing & oiling
• Silica-gel packing (keeps moisture away)
• Electroplating
• Galvanization (Zn-coating)

• Effect of corrosion
• Weakens metal structures, increases maintenance cost, safety hazards.

Alloys

• Definition: A metallic material composed of two or more metals or of metals with non-metals.
• Purpose: increases hardness, strength, chemical resistance, or tailors other properties.

• Common alloys & compositions
• Brass → Copper + Zinc
• Bronze → Copper + Tin
• Stainless steel → Iron + Chromium + Nickel (hard, rust-proof)
• German silver → Copper + Zinc + Nickel (hard, corrosion-resistant)

• Applications indicated in three-column match
• Brass … utensils, nails
• Bronze … statues
• Stainless steel … surgical instruments
• German silver … electric heaters (high electrical resistance)

Reactivity Series & Storage

• Sodium and potassium cannot be stored in ordinary packets; they are kept under kerosene because of violent reactivity with air & moisture.
• Metal reacting violently with cold water: sodium (magnesium reacts slowly).

Everyday Uses of Metals

• Electrical wires (Cu, Al)
• Coins, statues (Cu, Ni, Zn alloys)
• Cooking vessels, foils for wrapping chocolates/medicines (Al)
• Pipes, sinks, storage tanks, railings (Fe, steel)
• Utensils, cutlery, surgical tools (stainless steel, Ag)
• Mirrors (Ag coating – reflects almost 100 % of incident light)

Everyday Uses of Non-Metals

• Vegetable oil → ghee conversion (H₂ used for hydrogenation)
• Diamond in jewellery & cutting edges
• Liquid $N<em>2$ provides very low temperatures for organ storage • $O</em>2$ cylinders for medical use
• Fungicides & insecticides (S, P compounds)
• Manufacture of $H<em>2SO</em>4$ (S is a raw material)

Important Definitions & Units

• Malleability – ability to be beaten into sheets.
• Ductility – ability to be drawn into wires.
• Sonority – ability to produce a ringing sound.
• Carat – unit of gold purity; $24$-carat gold is pure.

Sample Numerical / Word Equations Discussed

1. Metal–water reactions (K, Na) already written above.

2. General metal–water equation:
   $\text{Metal} + H<em>2O \rightarrow \text{Metal oxide} + H</em>2\uparrow$

3. Acidic oxide formation when carbon burns:
   $C + O<em>2 \rightarrow CO</em>2$

High-Order Thinking Skills (HOTS) Notes

• Silver for mirrors → best reflector, lustrous.
• Iron for bridges/houses → very hard, high tensile strength.

Safety & Health Connection

• Acidic foods (pickles, curd) react with metal containers to form toxic salts; hence stored in glass/ceramic.

Quick Revision Lists

• Soft metals → $Na$, $K$ (can cut with knife).
• Liquid elements at room temp → Hg (metal) & Br₂ (non-metal).
• Best conductors → $Ag$ (theoretical), $Cu$ (practical).
• Protective oxide layer → $Al$ (prevents further corrosion).
• Metalloids → Sb, As, Te (show both metal & non-metal traits).

Reactivity Order Given in Exercise

• Asked to arrange: $Cu, K, Fe, Ag, Ca, Na, Zn, Au$ (increasing reactivity)
Answer listed: K < Na < Ca < Zn < Fe < Cu < Ag < Au (symbol ‘<’ here used by author though logically it should be reversed; remember full series for exams!)

Exam-Style Very-Short Answers (as per text)

1. Metal soft enough to cut → Sodium.

2. Best conductor of heat & electricity → Copper.

3. Two physical properties of non-metals → lack lustre, non-malleable/non-ductile, low m.p.

4. Do all metals give $H_2$ with dilute acids? → No.

5. Define corrosion → Destruction of a metal due to oxygen & moisture.

6. Unit of gold purity → Carat (24 carat = purest).

Memory Capsule

“Most metals are lustrous, malleable and ductile conductors that corrode except the noble few; their non-metal cousins are brittle, dull insulators that form acidic oxides – yet both are indispensable to life and industry.”