Big picture
Metals and non-metals are broad groups of elements with characteristic physical and chemical behaviour. Their properties explain why aluminium can become a thin sheet, copper can form a wire and sulphur cannot be hammered into a utensil. These are general patterns with important exceptions.
Choosing a material requires several properties together. A cooking pan needs to transfer heat, withstand use and remain suitable for food contact. An electric cable needs a conductor inside and an insulator outside. This lesson links observed properties to uses and explains reactions through carefully selected examples.
Learning goals
Compare physical properties of metals and non-metals with exceptions.
Relate malleability, ductility and conductivity to uses.
Explain reactions with oxygen, water and dilute acids.
Identify the nature of selected oxides using indicators.
Predict simple displacement reactions from relative reactivity.
Interpret activities, balanced equations and evidence without unsafe testing.
Core ideas
1. Elements, materials and classification
An element contains one kind of atom. Iron, copper and sulphur are elements; steel, brass and plastic are materials that need not be single elements. Brass is an alloy containing copper and zinc. Do not classify every shiny object as a pure metal merely from its surface.
Most familiar metals are solids at room temperature, while non-metals occur in different states. Mercury is a liquid metal under ordinary room conditions. Bromine is a liquid non-metal. Oxygen and nitrogen are gaseous non-metals. State alone therefore cannot identify every element's group.
2. Surface, sound and strength
Lustre is a characteristic shine on a suitable clean surface. Metals generally have metallic lustre, though corrosion or dirt can hide it. Iodine is a lustrous non-metal, so shine is not an infallible test.
Sonority is the ability to produce a ringing sound when struck. Metal bells exploit this property. A wooden block makes a sound too, but it does not normally ring like a metal bell. Many metals are strong, yet hardness varies: sodium is soft enough to cut with suitable equipment. Handling it is a teacher-controlled demonstration, not a pupil activity.
3. Malleability and ductility
Malleability means being shaped into sheets by hammering or rolling. Aluminium foil illustrates it. Ductility means being drawn into wires; copper wiring illustrates this property. These describe different changes of shape.
Many solid non-metals are brittle: they break rather than flatten under impact. Sulphur can crumble instead of becoming a sheet. A safe teacher-led comparison uses appropriate small samples and eye protection. Record whether a specimen flattens or fractures; do not strike unknown substances or batteries.
Property | General metal pattern | General non-metal pattern |
|---|---|---|
Lustre | Shiny when clean | Often dull; iodine is an exception |
Malleability | Often forms sheets | Usually brittle when solid |
Ductility | Often forms wires | Usually not drawable into wires |
Sonority | Often rings | Usually does not ring |
Conductivity | Usually good | Usually poor; graphite conducts electricity |
4. Heat and electrical conduction
A conductor allows heat or electric current to pass relatively easily. Copper and aluminium are useful electrical conductors. Metals in cookware transfer heat, while handles use less-conducting materials to reduce heat transfer to hands.
Graphite, a form of carbon, is a non-metal that conducts electricity. Diamond, another form of carbon, behaves differently. The same element can have forms with different structures and properties. Therefore “all non-metals are electrical insulators” is false.
In a low-voltage test circuit, place a specimen between two contacts in series with a cell and lamp. A glowing lamp supports electrical conduction. No glow may reflect poor contact or inadequate current, so inspect the circuit before classifying the material. Never use mains electricity for this comparison.
5. Reaction with oxygen
Many metals react with oxygen to form metal oxides. Magnesium burns with a bright light and forms white magnesium oxide: 2Mg + O₂ → 2MgO. Count two magnesium atoms and two oxygen atoms on each side.
Many metal oxides show basic behaviour. Magnesium oxide mixed with water forms a weakly alkaline mixture; moist red litmus turns blue. This observation links reaction product and indicator response. Do not stare at burning magnesium or handle hot products.
Non-metals also form oxides. Burning sulphur produces sulphur dioxide: S + O₂ → SO₂. Its solution in water is acidic and turns moist blue litmus red. Sulphur dioxide must not be inhaled; use a teacher's controlled demonstration or supplied observations.
6. Oxide behaviour has exceptions
The useful introductory pattern is “many metal oxides are basic; many non-metal oxides are acidic”. It is not universal. Aluminium oxide is amphoteric, meaning it can react with both acids and bases. Carbon monoxide is an example of a neutral oxide.
An indicator tests an appropriate aqueous mixture or solution, not simply a dry powder by appearance. A white powder does not prove basicity. Distinguish the observation, such as red litmus becoming blue, from the conclusion that the tested mixture is alkaline.
Test result | Supported conclusion |
|---|---|
Moist red litmus turns blue | The tested mixture is basic |
Moist blue litmus turns red | The tested mixture is acidic |
Neither changes | Further evidence may be needed; colour alone identifies no element |
7. Reaction with water
Metals differ greatly in reactivity. Sodium reacts vigorously with cold water and forms sodium hydroxide and hydrogen: 2Na + 2H₂O → 2NaOH + H₂. Heat can ignite the hydrogen. Sodium is kept away from water, commonly under kerosene in suitable laboratory storage.
Iron does not behave like sodium in cold water. Hot iron can react with steam: 3Fe + 4H₂O → Fe₃O₄ + 4H₂. Copper does not ordinarily liberate hydrogen from water under the conditions considered here.
The comparison demonstrates differing reactivity, not that all metals react with water. Most common non-metals do not react with water in this way. Storage choices depend on the particular element; do not place every metal under kerosene.
8. Reaction with dilute acids
Several metals react with suitable dilute acids to form a salt and hydrogen. Zinc with dilute hydrochloric acid gives Zn + 2HCl → ZnCl₂ + H₂. A trained teacher can test the evolved gas through the characteristic pop on ignition of a tiny controlled sample.
Copper does not release hydrogen with dilute hydrochloric acid under ordinary classroom conditions. Acid type matters; behaviour with an oxidising acid cannot automatically be predicted from this example. At this level, learn the stated conditions rather than claiming every metal produces hydrogen with every acid.
Common non-metals generally do not liberate hydrogen from these dilute acids. The gas test and reaction observations provide stronger evidence than whether a specimen looks shiny.
9. Displacement reactions and reactivity
A displacement reaction occurs when a more reactive metal replaces a less reactive metal from a suitable salt solution. Iron placed in blue copper sulphate solution can develop a reddish-brown copper coating, while the solution becomes greenish as iron sulphate forms: Fe + CuSO₄ → FeSO₄ + Cu.
Copper placed in iron sulphate solution does not reverse this reaction under the same conditions. This supports iron being more reactive than copper. Zinc can displace copper too: Zn + CuSO₄ → ZnSO₄ + Cu.
Use clean metal strips, comparable solutions and labelled containers in a teacher-supervised activity. A surface coating and colour change are observations; the reactivity conclusion follows from identifying the products. Temperature or concentration changes can affect reaction speed without reversing the basic comparison.
10. Uses follow combinations of properties
Material | Use | Relevant reason |
|---|---|---|
Copper | Electric wires | Conductivity and ductility |
Aluminium | Foil and utensils | Malleability, low density and heat conduction |
Iron-based alloys | Tools and structures | Suitable strength and workability |
Oxygen | Respiration and controlled medical supply | Its role in biological oxidation |
Nitrogen compounds | Fertilisers | Supply an essential plant nutrient |
Chlorine compounds | Controlled water disinfection | Appropriate disinfecting action |
Do not infer that oxygen itself burns: it supports combustion. Nor does a nutrient role mean applying arbitrary amounts is safe. Match the precise material and conditions to the use rather than assigning every property to a whole group without qualification.
11. Diagrams, evidence and quantitative checks
A useful circuit diagram labels cell, switch, lamp, wires and sample gap. A displacement diagram labels the iron strip, blue copper sulphate solution and later copper coating. The two diagrams test different properties, so a successful electrical test does not prove a displacement reaction will occur.
Worked numerical example: a wire costs ₹18 per metre. For 7 metres, cost = 18 × 7 = ₹126. If 2 metres remain unused, used length = 7 − 2 = 5 m, and the cost corresponding to that length is 5 × 18 = ₹90. Price does not identify the element; the calculation merely applies a material-use context.
A reliable approach to questions
Identify whether the question concerns a physical property or chemical change.
State the general pattern and any relevant exception.
For reactions, specify reactants and conditions before predicting products.
Balance atoms and distinguish observations from explanations.
For displacement, compare the two metals' reactivity.
Link a use to the particular properties it requires.
Connections that matter
Electrical effects use the conductor–insulator distinction.
Combustion explains oxidation and the role of oxygen.
Synthetic materials provide alternatives whose suitability depends on several properties.
Common mistakes
Calling every shiny solid a metal: iodine and coated materials challenge that shortcut.
Confusing sheets with wires: malleability and ductility describe different properties.
Predicting hydrogen from all metal–acid pairs: metal, acid and conditions matter.
Reversing displacement: the more reactive metal displaces the less reactive one.
Revision checklist
I can compare physical properties and explain exceptions.
I can describe conductor and indicator activities.
I can balance the stated oxidation and hydrogen-producing reactions.
I can infer relative reactivity from displacement evidence.
I can link material properties to uses.
I can distinguish a measured observation from a conclusion.