Alloys are among the most direct questions in general science. A name is given and you supply the composition, or a composition is given and you supply the name and its use. There is no reasoning involved and nothing ever changes, which makes this one of the few topics where an afternoon of memorising converts straight into marks. This post gives the composition table, groups the alloys by base metal, adds the uses that questions attach to them, and ends with previous year questions.
Key Points (Quick Revision)
- Brass = copper + zinc · Bronze = copper + tin
- Steel = iron + carbon · Stainless steel = iron + chromium + nickel + carbon
- German silver = copper + zinc + nickel — and contains no silver
- Solder = lead + tin · Duralumin = aluminium + copper + magnesium + manganese
- Amalgam = any alloy containing mercury
1. What an alloy is, and why we make them
An alloy is a homogeneous mixture of a metal with one or more other elements, which may themselves be metals or non-metals. Steel, for example, is iron mixed with carbon, and carbon is not a metal.
Alloys are made because pure metals are often unsuitable for use. Three properties usually improve:
- Hardness and strength. Pure iron is soft; adding a small amount of carbon gives steel, which is far stronger.
- Resistance to corrosion. Iron rusts; adding chromium and nickel gives stainless steel, which resists it.
- Lower melting point. Solder melts well below either of its constituents, which is exactly what is needed for joining electrical connections.
One property usually gets worse, and it is asked: alloying reduces electrical conductivity compared with the pure metal. That is why electrical wiring uses pure copper or aluminium rather than an alloy, even though the alloy would be stronger.
2. Copper-based alloys
| Alloy | Composition | Used for |
|---|---|---|
| Brass | Copper + zinc | Utensils, decorative items, musical instruments, fittings |
| Bronze | Copper + tin | Statues, medals, bells, coins |
| German silver | Copper + zinc + nickel | Ornaments and utensils; contains no silver |
| Gun metal | Copper + tin + zinc | Gears, bearings, machine parts |
| Bell metal | Copper + tin, with a higher tin proportion | Bells and gongs |
| Constantan | Copper + nickel | Thermocouples and resistance wire |
| Monel metal | Nickel + copper | Corrosion-resistant equipment |
Brass against bronze is the most asked pair in the whole topic. Brass is copper with zinc; bronze is copper with tin. Both begin with copper, which is why they appear as options against each other, and a candidate who fixes only one of them usually gets the other wrong.
German silver is the classic trick question. Despite the name it contains no silver at all — copper, zinc and nickel. If a paper asks which alloy contains no silver despite its name, this is the answer.
3. Iron-based alloys
| Alloy | Composition | Used for |
|---|---|---|
| Steel | Iron + carbon | Construction, tools, machinery |
| Stainless steel | Iron + chromium + nickel + carbon | Utensils, surgical instruments, cutlery |
| Invar | Iron + nickel | Clock pendulums and measuring tapes; expands very little on heating |
| Alnico | Aluminium + nickel + cobalt + iron | Permanent magnets |
| Nichrome | Nickel + chromium + iron | Heating elements in electric heaters and irons |
| Manganese steel | Iron + manganese + carbon | Railway tracks, crushing machinery, safes |
Two of these come with a property that is asked instead of the composition. Invar barely expands when heated, which is why it is used in pendulums and measuring instruments. Nichrome has high resistance and a high melting point, which is why it is used as the heating element rather than as a conductor.
Stainless steel is asked for the element that makes it rust-resistant, and that answer is chromium.
4. Aluminium, lead and other alloys
| Alloy | Composition | Used for |
|---|---|---|
| Duralumin | Aluminium + copper + magnesium + manganese | Aircraft and automobile parts; light and strong |
| Magnalium | Aluminium + magnesium | Light instruments and aircraft parts |
| Solder | Lead + tin | Joining electrical wires; low melting point |
| Type metal | Lead + antimony + tin | Printing type |
| Pewter | Tin + lead (older) or tin + antimony + copper | Utensils and decorative ware |
| Amalgam | Mercury + another metal | Dental fillings and extraction of metals |
| Dutch metal | Copper + zinc | Imitation gold leaf |
Duralumin is the aircraft answer. Its value is the combination of low density with strength close to that of steel, and questions usually frame it as the alloy used in aircraft bodies.
Amalgam is defined by mercury rather than by any fixed pair. Any alloy in which mercury is one component is an amalgam, and the standard example asked is the dental filling. Note that iron does not form an amalgam with mercury, which is a favourite question and the reason mercury can be stored in iron containers.
5. Alloys used in coins and jewellery
| Item | What it is |
|---|---|
| 22-carat gold | Gold alloyed with copper or silver; pure gold is 24 carat and too soft for jewellery |
| White gold | Gold alloyed with nickel, palladium or silver |
| Sterling silver | Silver alloyed with copper |
| Ferrous coinage | Modern Indian coins are largely made of stainless steel and ferritic steel |
Pure gold is 24 carat, and jewellery is made at 22 carat or lower because the pure metal is too soft to hold shape. That single fact answers a whole family of questions about carats and alloying.
6. Previous year questions
- Brass is an alloy of which two metals? — Copper and zinc
- Bronze is an alloy of copper and which metal? — Tin
- Which alloy contains no silver despite its name? — German silver
- German silver is composed of which metals? — Copper, zinc and nickel
- Steel is an alloy of iron and which element? — Carbon
- Which element makes stainless steel resistant to rusting? — Chromium
- Which alloy is used to make aircraft bodies? — Duralumin
- Duralumin contains which metals? — Aluminium, copper, magnesium and manganese
- Solder is an alloy of which two metals? — Lead and tin
- Which alloy is used in the heating element of an electric iron? — Nichrome
- An alloy containing mercury is called what? — Amalgam
- Which alloy is used to make bells? — Bell metal
- Which alloy is used in clock pendulums because it expands very little? — Invar
- Alnico is used to make what? — Permanent magnets
- Pure gold is of how many carats? — 24 carat
7. How to revise this topic
Group by base metal rather than alphabetically. Copper alloys, iron alloys, aluminium alloys, lead alloys. Almost every alloy asked belongs to one of those four families, and grouping means a blank on one name does not take the neighbouring ones with it.
Then learn the deliberate confusions as pairs. Brass and bronze both start with copper. Duralumin and magnalium both start with aluminium. Bell metal and gun metal are both copper-tin variants. Fix each pair in both directions and the topic mostly finishes itself.
Finally, learn the six alloys that are asked by use rather than by composition: Duralumin for aircraft, Nichrome for heating elements, Invar for pendulums, Alnico for magnets, Solder for wiring, Amalgam for dental fillings. Those six cover most application questions.
8. Frequently Asked Questions
What is the difference between brass and bronze?
Both are copper alloys. Brass is copper with zinc and is used for utensils, fittings and musical instruments. Bronze is copper with tin and is used for statues, medals, bells and coins. They are the most commonly confused pair in this topic.
Does German silver contain silver?
No. It is an alloy of copper, zinc and nickel, and contains no silver at all despite the name. Papers ask this specifically as a trick question about names that mislead.
Which alloy is used in aircraft?
Duralumin, an alloy of aluminium with copper, magnesium and manganese. It is valued for combining low density with strength comparable to steel, which is exactly what aircraft construction requires.
What is an amalgam?
Any alloy in which mercury is one of the components. The example usually asked is the dental filling. Iron does not form an amalgam with mercury, which is why mercury can be stored in iron containers, and that too is a question.
Why are alloys used instead of pure metals?
Because alloying usually increases hardness and strength, improves resistance to corrosion, or lowers the melting point where that is needed. The trade-off is that alloys conduct electricity less well than pure metals, which is why wiring uses pure copper or aluminium.
For more General Science topics in simple language, see our Metals and Non-Metals and Scientific Laws and Principles posts, or browse the General Science section. Preparing for a specific exam? Start with the SSC CGL guide or join the 100 Hour GS Course.