All objects around us — from the spoon we use to the pencil we write with — are made of materials, and these materials can be broadly divided into two groups: metals and non-metals. Metals are materials like iron, copper, gold, aluminium and silver that we associate with strength and shine, while non-metals include gases like oxygen and nitrogen, solids like sulphur, carbon and phosphorus, and liquids like bromine. About 118 elements are known today, of which roughly 22 are non-metals and the rest are metals.
We use different materials for different purposes precisely because they behave differently. A copper wire carries electricity, while a plastic covering insulates it; an iron nail is hard and strong, while charcoal (a form of carbon) crumbles easily. The properties that decide how and where a material is used — physical and chemical — are the subject of this chapter. Understanding these properties explains why metals and non-metals are used so differently in everyday life.
2. Physical Properties of Metals and Non-Metals
Physical properties can be observed without changing the material into a new substance. The important physical properties are:
State: Metals are generally solid at room temperature (mercury is the only metal that is liquid). Non-metals may be solid (sulphur, carbon), liquid (bromine) or gas (oxygen, nitrogen).
Lustre: Metals have a shiny appearance and are called lustrous. Non-metals are generally dull, though iodine and diamond (a form of carbon) show lustre.
Hardness: Metals are generally hard and strong; non-metals are generally soft, though diamond is the hardest natural substance.
Malleability: Metals can be beaten into thin sheets without breaking; this property is called malleability. Non-metals are not malleable — they break when beaten.
Ductility: Metals can be drawn into thin wires; this is called ductility. Non-metals are not ductile.
Conduction: Metals are good conductors of heat and electricity, which is why copper and aluminium are used in wires and cooking utensils. Non-metals (except graphite) are poor conductors.
Sonority: Metals are sonorous — they produce a ringing sound when struck. Non-metals are generally not sonorous.
Melting and boiling points: Metals generally have high melting and boiling points; non-metals have low melting and boiling points (though exceptions exist).
3. Chemical Properties of Metals and Non-Metals
Chemical properties describe how a material reacts with other substances. The important chemical properties are:
Reaction with oxygen: Metals react with oxygen to form basic oxides. For example, magnesium burns in air with a dazzling white flame to form magnesium oxide (MgO). Copper reacts slowly and forms a black coating of copper oxide. Non-metals react with oxygen to form acidic or neutral oxides; for example, sulphur burns to form sulphur dioxide, which dissolves in water to form an acidic solution.
Reaction with water: Some metals react with water to release hydrogen gas. Sodium and potassium react violently with cold water; calcium reacts less violently; iron reacts slowly with steam; and copper, silver and gold do not react with water. Non-metals generally do not react with water.
Reaction with acids: Metals react with dilute acids to release hydrogen gas, which burns with a pop sound. For example, zinc reacts with dilute hydrochloric acid to give zinc chloride and hydrogen. Non-metals generally do not react with dilute acids and do not release hydrogen.
Reaction with bases: Some metals react with bases to produce hydrogen gas; for example, aluminium reacts with sodium hydroxide solution. Generally non-metals do not react with bases in this way.
Reactivity series: Metals can be arranged in a series based on their reactivity, with potassium and sodium the most reactive, followed by calcium, magnesium, aluminium, zinc, iron, lead, copper, silver and gold the least reactive.
4. Reaction of Metals and Non-Metals with Each Other
When a metal reacts with a non-metal, an ionic compound is formed. For example, sodium (a metal) reacts with chlorine (a non-metal) to form sodium chloride (common salt). In this reaction, the metal atom loses electrons to become a positively charged ion (cation), and the non-metal atom gains electrons to become a negatively charged ion (anion). The oppositely charged ions are held together by strong electrostatic forces, forming a crystal lattice.
These ionic compounds have characteristic properties: they are usually crystalline solids, have high melting and boiling points, and conduct electricity when dissolved in water or melted. Ordinary salt, calcium oxide (quicklime) and magnesium chloride are all examples of ionic compounds formed by the reaction of metals with non-metals.
5. Uses of Metals and Non-Metals
Metals and non-metals are used according to their properties:
Uses of metals:
- Iron is used for making machines, tools and buildings.
- Copper and aluminium are used for electrical wires and cooking utensils because they are good conductors and ductile.
- Aluminium is light and is used in aeroplanes, foils and utensils.
- Gold and silver are used for jewellery because of their lustre and resistance to corrosion.
- Zinc is used for galvanising iron to prevent rusting.
- Mercury is used in thermometers.
Uses of non-metals:
- Oxygen is essential for breathing and combustion.
- Nitrogen is used in fertilisers and to preserve food.
- Hydrogen is used in the manufacture of ammonia and rocket fuel.
- Carbon (in the form of graphite) is used as a lubricant and in pencil leads, while diamond is used for cutting glass and in jewellery.
- Sulphur is used in making sulphuric acid, matches and gunpowder.
- Chlorine is used for purifying water.
6. Metal Ores, Rusting and Its Prevention
Metals are not found freely in nature (except less reactive ones like gold and silver); they are obtained from naturally occurring minerals called ores. An ore is a mineral from which a metal can be extracted profitably. For example, haematite is an ore of iron, bauxite is an ore of aluminium, and cinnabar is an ore of mercury.
Many metals react with air and moisture and get damaged over time. Rusting is the slow chemical change in which iron reacts with oxygen and moisture in the air to form a brown, flaky substance called rust. Rusting weakens iron objects. The rusting of iron requires both oxygen and moisture (or water). Methods to prevent rusting include:
- Painting the surface to keep air and moisture away.
- Applying oil or grease on tools and machine parts.
- Galvanisation: coating iron with a layer of zinc.
- Tinning: coating iron with tin (as in tin cans).
- Coating with plastic or enamel.
- Alloying: mixing iron with other metals (making stainless steel).
7. Alloys
Sometimes the properties of a metal are not enough, so we mix it with other metals or non-metals to get a more useful material. An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. Alloys are usually stronger, harder and more resistant to corrosion than the pure metals.
Stainless steel: iron + chromium + nickel — used for utensils and surgical instruments because it does not rust.
Brass: copper + zinc — used for decorative items and musical instruments.
Bronze: copper + tin — used for statues and medals.
Amalgam: an alloy of mercury with another metal — used in dental fillings.
Alloying is a smart way to combine the best properties of different materials into one.
Quick Revision Tables
Table 1: Physical Properties of Metals and Non-Metals
Property
Metals
Non-Metals
State
Solid (except mercury)
Solid, liquid or gas
Lustre
Lustrous (shiny)
Dull (except iodine, diamond)
Hardness
Generally hard
Generally soft (except diamond)
Malleability
Malleable (beat into sheets)
Non-malleable, break when beaten
Ductility
Ductile (drawn into wires)
Not ductile
Conduction
Good conductors of heat and electricity
Poor conductors (except graphite)
Sonority
Sonorous (ringing sound)
Not sonorous
Table 2: Chemical Properties
Reaction
Metals
Non-Metals
With oxygen
Form basic oxides
Form acidic or neutral oxides
With water
Release hydrogen (some metals)
Generally no reaction
With dilute acids
Release hydrogen gas
Generally no reaction
With bases
Some release hydrogen
Generally no reaction
Table 3: Common Alloys and Their Uses
Alloy
Composition
Uses
Stainless steel
Iron + chromium + nickel
Utensils, surgical instruments
Brass
Copper + zinc
Decorative items, musical instruments
Bronze
Copper + tin
Statues, medals
Amalgam
Mercury + another metal
Dental fillings
Mind Map
graph TD
A["Materials: Metals and Non-Metals"] --> B["Physical Properties"]
B --> B1["Lustre, hardness, malleability, ductility"]
B --> B2["Conduction of heat and electricity"]
B --> B3["Sonority, state"]
A --> C["Chemical Properties"]
C --> C1["React with oxygen: basic vs acidic oxides"]
C --> C2["React with water and acids: release hydrogen"]
C --> C3["Reactivity series"]
A --> D["Metals + Non-Metals"]
D --> D1["Ionic compounds (e.g. NaCl)"]
A --> E["Rusting and Prevention"]
E --> E1["Painting, oiling, galvanisation"]
E --> E2["Alloying, tinning"]
A --> F["Alloys"]
F --> F1["Stainless steel, brass, bronze"]
Important Diagrams (SVG)
Diagram 1: Physical Properties of Metals vs Non-Metals
Diagram 2: Rusting and Its Prevention
Common Mistakes
Thinking all metals are harder than non-metals: Diamond (a non-metal form of carbon) is the hardest natural substance, while sodium and potassium are soft metals.
Believing all metals are solids: Mercury is a metal that is liquid at room temperature — the only such metal.
Claiming no non-metal conducts electricity: Graphite, a non-metal, is a good conductor of electricity and is used in pencil leads.
Saying metals react with acids to form chlorine: Metals release hydrogen gas when they react with dilute acids, not chlorine.
Forgetting both conditions for rusting: Rusting needs oxygen AND moisture; either one alone is insufficient.
Calling brass a metal: Brass is an alloy (copper + zinc), a homogeneous mixture, not a pure metal.
Saying all metal oxides are basic: While most metal oxides are basic, some like aluminium oxide and zinc oxide are amphoteric (react with both acids and bases). Generally for Class 8 we say metal oxides are basic.
Confusing an ore with an alloy: An ore is a mineral from which a metal is extracted; an alloy is a mixture of metals made deliberately.
Exam Tips
Learn one example for every property: lustre (gold), ductility (copper wire), malleability (aluminium foil), sonority (bell).
In "uses" questions, justify with a property: copper for wires because it is a good conductor and ductile.
Conclusion
Metals and non-metals differ in almost every physical and chemical property — in lustre, hardness, malleability, ductility, conduction, sonority, and in how they react with oxygen, water and acids. These differences decide their uses: metals for wires, utensils, tools and jewellery, and non-metals for fertilisers, fuels, medicines and water purification. The reaction between a metal and a non-metal produces ionic compounds such as sodium chloride, which make up so many important substances around us. The menace of rusting can be controlled through painting, oiling, galvanisation and alloying. By understanding the properties of materials, we can choose the right material for the right purpose and protect our metal articles for longer.