Metals, ores and alloys

Solder

50% tin; 50% lead. Lower melting point than tin and lead. (800°C for pure; 160°C for solder). Use for computer micro-chips

Brass

70% copper; 30% zinc. More corrosion-resistant than copper and zinc itself. Use for bearings and gears, musical instruments.

Stainless steel

70% iron; 20% chromium; 9.5% nickel; 0.5% carbon. Do not rust and more corrosion-resistant. Use for dining utensils, cooking utensils, water tap, watch.

Bronze

88% copper; 12% tin. Harder and more corrosion-resistant. Use for weapons, ship propellers, bronze medal.

Duralumin

95% aluminium (corrosion-resistant); 3% copper; 1% magnesium; 1% manganese. Light and hard. Use for frames of trains and planes.

Characteristics of alloy

Alloying one metal with other metal(s) or non-metal(s) often enhance its properties. Alloys usually have different properties from those of the component elements.

Bauxite

Aluminium (also for potassium, sodium, calcium and magnesium); electrolysis of molten aluminium

Alloy

An alloy is formed when one or more elements are added to a metal to form a uniform mixture.

Metamorphic rocks

An example is marble.

CaCo3

Chemical symbol of calcium carbonate

Copper pyrite

Copper; heating ores with carbon (reducing agent)

Sedimentary rocks

Examples are chalk and limestones.

Heating oreas with carbon

Extraction method for more reactive metals. Zinc(Zn), iron(Fl), lead(Pb), copper(Cn)

Heating ores alone

Extraction method for non-reactive metals only. Silver(Ag), mercury(Hg)

Electrolysis of molten ores

Extraction method for very reactive metals. Potassium(K), sodium(Na), calcium(Ca), magnesium(Mg), aluminium(Al). E.g. Aluminium Oxide (l) =electrolysis=> aluminium + oxygen

Gold alloy

Gold; silver; copper. Harder than gold. Carat is a measure of purity of gold, e.g. 24-carat gold is fine (99%) and 18-carat gold is 75% gold. Use for jewelry.

Haematite

Iron; heating ores with reducing agent7

Galena

Lead; heating ores with carbon (reducing agent)

Why would there be marble?

Movement of the Earth's crust may cause the layers to sink further and higher pressure and heat may cause the chalk into much harder limestone. After a loner period of time and under higher temperature and pressure, limestone may turn into marble.

Calcium carbonate

Occurs naturally in 3 forms: (1) chalk - softest; (2) limestone - harder than chalk; (3) marble - hardest.

Ores

Rocks from which we obtain the metals are called ores.

Minerals

The individual chemical compound that make up rocks are called minerals. The mineral can be solid element (e.g. graphite) or a chemical compound (quartz).

Extracting metals from their ores

To obtain a pure metal from its ores, the following processes are usually involved: (1) Mining the ore; (2) Concentrating the ore; (3) Extracting the metal from the concentrated ore

Why would there be chalk on Earth?

When aquatic life die, their skeletons or shells - which are made up of calcium carbonate - sink into the mud at the bottom of the oceans. Over millions of years layers build up. Pressure from the top layers changes the bottom layers into chalk. Earth movements such as earthquakes may lift the chalk to the Earth's surface.