Last reviewed: 7 November 2026
Updated November 2026. These Grade 9 metals and alloys notes cover the physical properties of metals, the composition and uses of common alloys (steel, stainless steel, bronze, brass and duralumin), uses of common metals, and the causes, effects and prevention of rusting. An alloy is a mixture of a metal with one or more other elements, made to improve properties such as hardness or resistance to corrosion. Brass, for example, is mainly copper and zinc.
The questions are original practice for Kenyan junior school learners, not an official paper. For other Grade 9 science topics, see the Grade 9 Integrated Science revision guide and the Grade 9 notes hub.
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What the Grade 9 Curriculum Covers
Metals and alloys is a sub-strand under Mixtures, Elements and Compounds in the Kenya Institute of Curriculum Development’s Grade 9 Integrated Science design. It covers physical properties of metals (state, ductility, malleability, electrical and thermal conductivity); composition of steel, stainless steel, bronze, brass and duralumin; uses of sodium, magnesium, aluminium, copper, iron, gold, silver and those alloys; and rusting. The design is listed on the KICD Grade Nine curriculum designs page.
Physical Properties of Metals
| Property | Meaning | Everyday example |
|---|---|---|
| State | Most metals are solid at room temperature; mercury is a liquid | Iron nails, copper wire |
| Malleability | Can be hammered into thin sheets without breaking | Aluminium foil, iron sheets (mabati) |
| Ductility | Can be drawn into wires | Copper electrical wire |
| Electrical conductivity | Allow electric current to flow | Copper and aluminium cables |
| Thermal conductivity | Conduct heat well | Aluminium sufurias |
| Lustre | Shiny when freshly cut or polished | Gold and silver jewellery |
Simple class experiments
- Conductivity: connect a dry cell, bulb and wires, and touch the free ends to a nail, a copper wire, a plastic ruler and a piece of wood. The bulb lights for the metals only.
- Heat conduction: hold one end of a metal rod and one end of a wooden rod near warm water (never a flame directly, and only under supervision). The metal end gets warm faster.
- Malleability: gently hammer a thin piece of aluminium on a hard surface; it flattens rather than shattering.
Common Alloys and Their Composition
| Alloy | Main components | Useful property | Uses |
|---|---|---|---|
| Steel | Iron and a small amount of carbon | Stronger and harder than pure iron | Building rods, bridges, tools |
| Stainless steel | Iron, chromium (often nickel) and carbon | Resists rusting | Cutlery, sinks, surgical tools |
| Brass | Copper and zinc | Hard, golden colour, resists corrosion | Door handles, padlocks, musical instruments |
| Bronze | Copper and tin | Hard, resists corrosion | Medals, statues, bearings |
| Duralumin | Aluminium with copper (and small amounts of magnesium and manganese) | Light but strong | Aircraft bodies, bicycle parts |
Uses of Common Metals
- Sodium: a very reactive metal kept under paraffin; its compounds, like sodium chloride (table salt), are widely used. Sodium vapour is used in some street lamps.
- Magnesium: burns with a bright white flame (used in flares); also used in light alloys.
- Aluminium: cooking pots, window frames, foil and overhead power cables, because it is light, conducts well and resists corrosion.
- Copper: electrical wiring and water pipes.
- Iron: mainly made into steel for construction and machines.
- Gold and silver: jewellery and electronics contacts, because they do not tarnish easily (gold) and conduct well.
Rusting: Causes, Effects and Prevention
Rusting is the corrosion of iron and steel. It needs both oxygen (air) and water; salt and acids speed it up, which is why cars and iron sheets near the coast rust faster. Rust is mainly hydrated iron(III) oxide, a flaky reddish-brown solid. OpenStax Chemistry’s section on corrosion explains rusting and how coatings and sacrificial metals protect iron.
Effects
Weakened bridges, gates and roofs; leaking tanks and pipes; and money spent on repairs and replacements.
Prevention
- Painting, oiling or greasing to keep out air and water.
- Galvanising: coating iron with zinc, as on many iron sheets. Zinc corrodes first, protecting the iron.
- Plastic coating, as on some wire fences.
- Using stainless steel where rust must be avoided.
A simple investigation
Set up three nails: one in tap water open to the air, one in boiled water covered with a layer of oil (no air), and one in a dry, closed container with a drying agent (no water). After a few days, only the nail with both air and water should show clear rust.
Original Practice Questions With Worked Answers
- Which property allows copper to be made into wires? Ductility.
- Name the two main metals in brass. Copper and zinc.
- Why are aircraft bodies made from duralumin rather than steel? Duralumin is much lighter but still strong.
- State two conditions needed for rusting. Oxygen (air) and water.
- Why do iron sheets near Mombasa rust faster than those in a dry area? Moist, salty air speeds up rusting.
Cover the answers and attempt each question first. For timed practice, use the Grade 9 revision papers or the Grade 9 CBC Challenge. These notes are free; full revision access is available with the KSh 20 Day Pass or the KSh 500 Monthly Pass.
Frequently Asked Questions
What is an alloy?
A mixture of a metal with one or more other elements, made to give better properties such as strength or resistance to rusting.
What is the difference between brass and bronze?
Brass is mainly copper and zinc; bronze is mainly copper and tin.
What causes rusting?
Iron or steel reacting with oxygen in the presence of water. Salt speeds it up.
How can rusting be prevented?
By painting, oiling or greasing, galvanising with zinc, plastic coating, or using stainless steel.