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Students often learn metals and non-metals as a list of adjectives and then get stuck on the exceptions: a soft metal, a liquid metal, a material that is neither. This guide explains each property through the test that shows it, works through two short calculations, and lists the traps.
Where is this topic in the 2026-27 NCERT books?
The main chapter is now in Class 7: Curiosity Grade 7, Chapter 4, "The World of Metals and Non-metals". The new Class 8 book builds on it in Chapter 8, "Nature of Matter: Elements, Compounds, and Mixtures", which adds metalloids, alloys and minerals. There is no separate metals chapter in the Class 8 Curiosity contents. You meet the topic again, in more depth, in Class 10; see our guide to metals and non-metals in Class 10.
How do you tell a metal from a non-metal?
Each property comes with a simple test in the Class 7 book.
Lustre: copper, aluminium and iron shine; coal and sulfur look dull.
Malleability: beat a sample with a hammer. Metals flatten into sheets; coal and sulfur break, so they are brittle. Gold and silver are the most malleable metals.
Ductility: metals can be drawn into wires. The book says one gram of gold can be drawn into a wire about 2 km long.
Sonority: a dropped coin rings; coal and wood give a dull sound.
Conducting heat: in hot water, a metal spoon's handle gets hot and a wooden one does not.
Conducting electricity: in a simple tester circuit, aluminium foil, an iron nail and copper wire light the bulb; sulfur, coal, wood and rubber do not.
What happens when metals and non-metals meet air and water?
This is where the chemistry is, and where exam questions come from.
Rusting. The book's experiment uses three iron nails: one in dry air with silica gel, one in boiled water under a layer of oil, and one partly in water and open to air. Only the third rusts. So rusting needs both air and water. Rusting is one kind of corrosion; copper turns green and silver turns black. Painting, oiling and galvanising (a zinc coat) protect iron.
Oxides. Magnesium burns with a bright white flame to give magnesium oxide, which turns red litmus blue: it is basic. Sulfur burns to give sulfur dioxide, which dissolves in water to give an acidic solution. The rule: metal oxides are generally basic, non-metal oxides acidic.
Storage. Sodium is kept in kerosene because it reacts strongly with air and water. Phosphorus is kept under water because it catches fire in air.
What are metalloids and alloys?
The Class 8 book adds two ideas. Metalloids, such as silicon and boron, have properties between those of metals and non-metals. Alloys are mixtures of metals, or of a metal and a non-metal, with properties different from their parts: brass is copper and zinc, bronze is copper and tin, and steel is iron with carbon. It also notes that of the 118 known elements, eleven are gases at room temperature (all non-metals), and only two are liquids: mercury, a metal, and bromine, a non-metal.
Two worked examples
Example 1: alloy proportions. The Class 8 book describes bronze (kamsya) as 4 parts copper to 1 part tin. How much of each is in a 500 g bronze bowl?
Total parts = 4 + 1 = 5. Copper = 4/5 × 500 = 400 g. Tin = 1/5 × 500 = 100 g. As a percentage, copper is 4/5 = 80% of the bowl.
Check: 400 + 100 = 500 g.
Example 2: how thin is a gold wire? If 1 g of gold makes about 2 km of wire, what mass of gold is in one metre?
2 km = 2,000 m. Mass per metre = 1 g ÷ 2,000 = 0.0005 g = 0.5 mg.
A common slip is to forget to change kilometres to metres and get 0.5 g per metre, a thousand times too heavy.
What traps should you watch for?
"All metals are hard." Sodium and potassium are soft enough to cut with a knife.
"All metals are solid." Mercury is liquid at room temperature.
"Copper pots are used because copper conducts electricity." The Class 7 exercise tests this: it is because copper conducts heat.
"Sulfur does not react with water, so it could coat iron like zinc." The book asks you to judge this. A good answer uses properties: zinc is a metal that can form a continuous coat, while sulfur is brittle and crumbles. Give reasons, not one word.
Litmus colours reversed. Basic turns red litmus blue; acidic turns blue litmus red.
A practice routine
Make a two-column table, metals and non-metals, with one test per property. Fill it from memory, then check.
Write the three-nail rusting experiment as a prediction, then explain each result.
Write word equations for burning magnesium and sulfur, with the litmus result for each oxide.
Do one mixture-ratio question with a new alloy ratio, and check the parts add back to the total.
If you are not sure why magnesium oxide is basic but sulfur dioxide is acidic, the Fermi Concept Library covers every concept in physics, chemistry, biology, mathematics and computing, so you can read the idea and come back to the chapter. Our post on whether matter is pure in Class 9 is the next step up on elements and mixtures.
Today, collect five objects at home and sort them into metal, non-metal and neither, with one test for each.
