The Metal You Can Pour and the Non-Metal That Conducts
Learn the physical properties of metals and non-metals with every exception, why metals form basic oxides, what brass, bronze, steel and solder are made of, and six ways to stop iron rusting.
Are there metals that behave like non-metals?
Yes, and the exceptions are where most marks are won. Mercury is a metal you can pour like water, sodium is a metal soft enough to cut with a knife, and graphite is a non-metal that conducts electricity.
Every rule in this chapter has one or two of these. This page covers everything in the ICSE Class 7 Chemistry chapter on metals and non-metals: their physical properties, classification and oxides, alloys and uses, and corrosion with its prevention.
Every rule in this chapter has one or two of these. This page covers everything in the ICSE Class 7 Chemistry chapter on metals and non-metals: their physical properties, classification and oxides, alloys and uses, and corrosion with its prevention.
How do the physical properties of metals and non-metals compare?
Metals and non-metals differ on eight properties, and each has a familiar exception.
- Lustre — metals are shiny; non-metals are dull. Exception: iodine and diamond are lustrous non-metals.
- Malleability — metals can be beaten into thin sheets; non-metals are brittle. Gold foil and aluminium foil show this.
- Ductility — metals can be drawn into wires; non-metals cannot.
- Hardness — metals are generally hard. Exceptions: sodium and potassium are soft enough to cut with a knife, and diamond, a non-metal, is the hardest natural substance.
- Conductivity — metals conduct heat and electricity well; non-metals do not. Exception: graphite conducts electricity.
- Sonority — metals give a ringing sound when struck; non-metals do not. This is why temple bells are metal.
- Density — metals are usually dense. Exceptions: sodium and potassium are lighter than water and float on it.
- Melting and boiling points — metals are usually high. Exceptions: mercury is a liquid at room temperature, while gallium melts in the hand.
A kitchen shows the pattern directly: a steel vessel conducts heat to the food and rings when tapped, while the plastic on its handle does neither.
The exception you must be able to name in both directions is the pair of liquids — mercury among metals, and bromine among non-metals.
- Lustre — metals are shiny; non-metals are dull. Exception: iodine and diamond are lustrous non-metals.
- Malleability — metals can be beaten into thin sheets; non-metals are brittle. Gold foil and aluminium foil show this.
- Ductility — metals can be drawn into wires; non-metals cannot.
- Hardness — metals are generally hard. Exceptions: sodium and potassium are soft enough to cut with a knife, and diamond, a non-metal, is the hardest natural substance.
- Conductivity — metals conduct heat and electricity well; non-metals do not. Exception: graphite conducts electricity.
- Sonority — metals give a ringing sound when struck; non-metals do not. This is why temple bells are metal.
- Density — metals are usually dense. Exceptions: sodium and potassium are lighter than water and float on it.
- Melting and boiling points — metals are usually high. Exceptions: mercury is a liquid at room temperature, while gallium melts in the hand.
A kitchen shows the pattern directly: a steel vessel conducts heat to the food and rings when tapped, while the plastic on its handle does neither.
The exception you must be able to name in both directions is the pair of liquids — mercury among metals, and bromine among non-metals.
Why do metals form basic oxides and non-metals acidic ones?
Because metals are electropositive and their oxides react with water to give bases, while non-metals give acids.
First the classification of elements:
- Metals — iron, copper, aluminium, zinc, gold, silver, sodium, calcium.
- Non-metals — carbon, sulphur, phosphorus, oxygen, nitrogen, chlorine, iodine.
- Metalloids — silicon, germanium, arsenic, antimony, boron; they show properties of both.
- Noble gases — helium, neon, argon, krypton, xenon, radon; chemically almost unreactive.
Now the oxides. A metal oxide is basic: sodium oxide dissolves in water to give sodium hydroxide, which turns red litmus blue. A non-metal oxide is acidic: carbon dioxide dissolves to give carbonic acid, and sulphur dioxide gives sulphurous acid, both of which turn blue litmus red.
Quicklime stirred into water for whitewash is the everyday basic oxide, and the fizz of a cold drink is dissolved carbon dioxide making a weak acid.
This is the property that decides an element's chemical family, and it is more reliable than appearance. Graphite looks metallic and conducts, yet its oxide is acidic — so chemically it is firmly a non-metal.
First the classification of elements:
- Metals — iron, copper, aluminium, zinc, gold, silver, sodium, calcium.
- Non-metals — carbon, sulphur, phosphorus, oxygen, nitrogen, chlorine, iodine.
- Metalloids — silicon, germanium, arsenic, antimony, boron; they show properties of both.
- Noble gases — helium, neon, argon, krypton, xenon, radon; chemically almost unreactive.
Now the oxides. A metal oxide is basic: sodium oxide dissolves in water to give sodium hydroxide, which turns red litmus blue. A non-metal oxide is acidic: carbon dioxide dissolves to give carbonic acid, and sulphur dioxide gives sulphurous acid, both of which turn blue litmus red.
Quicklime stirred into water for whitewash is the everyday basic oxide, and the fizz of a cold drink is dissolved carbon dioxide making a weak acid.
This is the property that decides an element's chemical family, and it is more reliable than appearance. Graphite looks metallic and conducts, yet its oxide is acidic — so chemically it is firmly a non-metal.
What are brass, bronze, steel and solder made of?
An alloy is a homogeneous mixture of two or more metals, or of a metal with a non-metal, made to improve on the properties of the pure metal.
- Brass — copper and zinc. Used for utensils, taps, door fittings and musical instruments.
- Bronze — copper and tin. Used for statues, medals and bells.
- Steel — iron and carbon. Used for construction, rails, tools and vehicles.
- Solder — lead and tin. Used for joining electrical wires, because it melts at a low temperature.
Alloying works because the added metal changes the structure. Pure iron is comparatively soft and rusts readily, while steel is far stronger, and stainless steel — iron with chromium and nickel — resists rust altogether.
The uses of the pure elements follow their properties too: copper for wiring because it conducts, aluminium for foil and aircraft because it is light and malleable, graphite for pencil leads and motor brushes, and sulphur for making sulphuric acid.
The point examiners test is that an alloy is a mixture, not a compound. Brass has no fixed formula, its proportions can be varied to make it harder or softer, and its copper and zinc are not chemically combined.
- Brass — copper and zinc. Used for utensils, taps, door fittings and musical instruments.
- Bronze — copper and tin. Used for statues, medals and bells.
- Steel — iron and carbon. Used for construction, rails, tools and vehicles.
- Solder — lead and tin. Used for joining electrical wires, because it melts at a low temperature.
Alloying works because the added metal changes the structure. Pure iron is comparatively soft and rusts readily, while steel is far stronger, and stainless steel — iron with chromium and nickel — resists rust altogether.
The uses of the pure elements follow their properties too: copper for wiring because it conducts, aluminium for foil and aircraft because it is light and malleable, graphite for pencil leads and motor brushes, and sulphur for making sulphuric acid.
The point examiners test is that an alloy is a mixture, not a compound. Brass has no fixed formula, its proportions can be varied to make it harder or softer, and its copper and zinc are not chemically combined.
What are the two conditions needed for iron to rust?
Air (oxygen) and moisture (water) — and rusting stops if either one is removed.
Corrosion is the slow eating away of a metal's surface by the action of air, moisture or chemicals. On iron it is called rusting, and the product is hydrated iron oxide — a reddish-brown, flaky solid quite unlike the grey metal beneath.
That is why iron gates rust fast in the monsoon, why a nail in dry sand can stay bright for months, and why a bicycle chain rusts at the spots where the oil has worn away.
Six methods of prevention appear in the syllabus, and each works by keeping air and water off the iron:
- Painting — a coat of paint on gates, grilles and bridges.
- Oiling and greasing — used on tools, machine parts and cycle chains.
- Galvanising — coating iron with a layer of zinc, used for roofing sheets, buckets and pipes.
- Tinning — coating with tin, used for food cans because tin is non-poisonous.
- Electroplating — depositing a thin layer of another metal, such as chromium or nickel, by passing an electric current.
- Alloying — converting the iron into stainless steel, which does not rust at all.
The distinction between the coatings is worth fixing: galvanising uses zinc, tinning uses tin. And a scratch matters — a broken paint layer lets both air and water reach the iron, so rusting begins exactly at the scratch.
Corrosion is the slow eating away of a metal's surface by the action of air, moisture or chemicals. On iron it is called rusting, and the product is hydrated iron oxide — a reddish-brown, flaky solid quite unlike the grey metal beneath.
That is why iron gates rust fast in the monsoon, why a nail in dry sand can stay bright for months, and why a bicycle chain rusts at the spots where the oil has worn away.
Six methods of prevention appear in the syllabus, and each works by keeping air and water off the iron:
- Painting — a coat of paint on gates, grilles and bridges.
- Oiling and greasing — used on tools, machine parts and cycle chains.
- Galvanising — coating iron with a layer of zinc, used for roofing sheets, buckets and pipes.
- Tinning — coating with tin, used for food cans because tin is non-poisonous.
- Electroplating — depositing a thin layer of another metal, such as chromium or nickel, by passing an electric current.
- Alloying — converting the iron into stainless steel, which does not rust at all.
The distinction between the coatings is worth fixing: galvanising uses zinc, tinning uses tin. And a scratch matters — a broken paint layer lets both air and water reach the iron, so rusting begins exactly at the scratch.
Exam tip
Exam tip: naming the exception with the property
This chapter is graded on precision, and three habits secure the marks.
When a property is asked for, add its exception in the same breath: metals are hard, except sodium and potassium which can be cut with a knife. The exception is often a separate mark.
For alloys, name both constituents and one use. "Brass is an alloy" earns nothing; brass is copper and zinc, used for utensils and taps earns full credit.
For rusting, always give both conditions — air and moisture — and name the product as hydrated iron oxide, not just "rust".
Use the litmus result when asked about an oxide. A metal oxide is basic and turns red litmus blue; a non-metal oxide is acidic and turns blue litmus red.
And keep galvanising and tinning apart: zinc for the first, tin for the second.
When a property is asked for, add its exception in the same breath: metals are hard, except sodium and potassium which can be cut with a knife. The exception is often a separate mark.
For alloys, name both constituents and one use. "Brass is an alloy" earns nothing; brass is copper and zinc, used for utensils and taps earns full credit.
For rusting, always give both conditions — air and moisture — and name the product as hydrated iron oxide, not just "rust".
Use the litmus result when asked about an oxide. A metal oxide is basic and turns red litmus blue; a non-metal oxide is acidic and turns blue litmus red.
And keep galvanising and tinning apart: zinc for the first, tin for the second.
Did you know
Why does a zinc coating protect iron even where it is scratched?
Because zinc is more reactive than iron, so it corrodes instead of the iron underneath.
A painted surface protects only where the paint is unbroken — scratch it and the exposed iron begins to rust immediately. Galvanised iron behaves differently: even at a scratch, the surrounding zinc is attacked in preference, and the iron is left alone.
That is why galvanised roofing sheets and buckets survive years of monsoon rain, and why zinc is described as a sacrificial coating — it gives itself up to save the iron.
A painted surface protects only where the paint is unbroken — scratch it and the exposed iron begins to rust immediately. Galvanised iron behaves differently: even at a scratch, the surrounding zinc is attacked in preference, and the iron is left alone.
That is why galvanised roofing sheets and buckets survive years of monsoon rain, and why zinc is described as a sacrificial coating — it gives itself up to save the iron.
Key takeaways
Metals, non-metals and alloys: quick revision
- Metals are lustrous, malleable, ductile, hard, sonorous, dense and good conductors; non-metals are generally the opposite.
- Learn the exceptions: mercury is a liquid metal, bromine a liquid non-metal, sodium and potassium are soft and float, graphite conducts, and iodine and diamond are lustrous.
- Metal oxides are basic and turn red litmus blue; non-metal oxides are acidic and turn blue litmus red.
- Elements are metals, non-metals, metalloids or noble gases, and the oxide's nature is the reliable chemical test.
- Alloys are mixtures: brass is copper and zinc, bronze copper and tin, steel iron and carbon, solder lead and tin.
- Rusting needs air and moisture together, and is prevented by painting, oiling, galvanising with zinc, tinning with tin, electroplating or alloying into stainless steel.
You will remember all of this far better after answering five questions on it than after reading it twice.
- Learn the exceptions: mercury is a liquid metal, bromine a liquid non-metal, sodium and potassium are soft and float, graphite conducts, and iodine and diamond are lustrous.
- Metal oxides are basic and turn red litmus blue; non-metal oxides are acidic and turn blue litmus red.
- Elements are metals, non-metals, metalloids or noble gases, and the oxide's nature is the reliable chemical test.
- Alloys are mixtures: brass is copper and zinc, bronze copper and tin, steel iron and carbon, solder lead and tin.
- Rusting needs air and moisture together, and is prevented by painting, oiling, galvanising with zinc, tinning with tin, electroplating or alloying into stainless steel.
You will remember all of this far better after answering five questions on it than after reading it twice.