Metals: Magnesium, Lead & Copper Uses

Magnesium

• Silvery-white metal usually in ribbon form.
• Burns with a dazzling white flame.

Common uses of magnesium

• Manufacturing fireworks(Fig 6.7).
• Alloyed to make aircraft, automobiles, and machinery parts.
• Used to make fuse wires.

Lead

• Silvery-grey color.

Common uses of lead

• Making storage batteries.
• Component of solder for joining electric circuits (Fig 6.8).
• Radiation shielding.
• Making bullet tips.

Copper

• Reddish-brown color.
• Good conductor of heat and electricity, easily drawn into wires.

Common uses of copper

• Making wires (Fig 6.9) and cables for electrical purposes.
• Alloying with brass and bronze for statues and coins.
• Making utensils, coins, statues, and jewelry.

Elements in Minerals

• Elements like iron, aluminum, copper, calcium, magnesium, sodium, and potassium present in minerals in combined states.
• Ores are rocks that contain a large amount of a certain metal or metallic compound from which the metal can be extracted.
• Examples of ores include haematite and magnetite for iron, galena for lead, bauxite for aluminium and chalcocite for copper.
• Impurities or gangue are other substances present in an ore, along with the useful metal.
• Highly reactive metals are present in their ores as oxides, carbonates, sulphates, and sulphides.
• Gold and silver occur in free state and known as noble metals because they are not very reactive.

Non-Metals

• Occur in combined state, while some like sulfur and iodine exist as solids at room temperature.
• Found in Earth's crust and atmosphere in free or combined states.
• Hydrogen is the most abundant element/non-metal in the universe.
• It makes up celestial objects like the Sun and other stars.
• Oxygen is the most abundant element on Earth found in combined state in water.
• In its free state, it forms about one-fourth of the atmosphere.
• Nitrogen is mainly found in free state in the atmosphere composing more than three-fourths of it.
• Carbon is found in free and combined states.

Ions

• Metals liberate electrons to produce cations and hence are called electropositive substances.
• Non-metals accept electrons to produce anions and hence are called electronegative substances.

Wonderment

• Hydrogen is a highly inflammable non-metal that burns with a 'pop' sound producing a blue flame.

Common uses of non-metals: Carbon

• Carbon (Fig. 6.10 Diamond, Fig. 6.11 Charcoal, Fig. 6.12 Liquid oxygen): Present as carbon dioxide gas in the atmosphere and in free state as diamond, graphite, coal and charcoal.
• Diamond: Crystalline form, used in jewellery and is hardest natural substance for cutting glass/rocks.
• Graphite: Soft, slippery, grey-black, lustrous, lubricant in machine parts, makes pencil leads, is a good conductor in electric cells and batteries.
• Coal: Fuel for homes/industries.
• Charcoal: Porous, black solid obtained by heating wood in limited air, used in gas masks, gunpowder, water filtration, decolourising agent.

Oxygen and other non-metals

• Oxygen is essential for respiration.
• Oxygen supports burning, used in hospitals, mountaineering, welding (oxy-acetylene torch), and as rocket fuel (liquid oxygen).
• Ozone, an allotrope, purifies water.
• Nitrogen occupies a large portion of the atmosphere and counters combustion.
• Liquid nitrogen is a low-temperature coolant (-195.8°C), and it also preserves human body parts.
• Nitrogen makes TNT, fertilizers, and non-reactive food packaging. .

Common uses of Chlorine and metals

• Chlorine is a highly reactive, greenish-yellow gas with a pungent smell.
• Chlorine disinfects, bleaches chemically, is used to manufacture insecticides (BHC), extracts titanium/germanium, prepares hydrochloric acid, and is used to make PVC plastics.
• Metalloids: Including Boron, silicon, germanium, antimony and arsenic are substances having properties of metals/non-metals; brittle solids, not conduct electricity, are semiconductors, alloys, flame-retardants, glasses and catalysts.

General properties of metals and non-metals(physical state)

• Most Metals are solid at room temperature.
• Mercury is the only liquid metal that is liquid at room temperature.
• Gallium is another metal that is in liquid form at a temperature above 30°C.
• Most Non-metals exist as gases at room temperature with the exception of carbon, sulfur and bromine.
• Oxygen, nitrogen and chlorine are non-metals that exist as gases.
• Bromine is the only non-metal that exists as a liquid at room temperature.)

State of hardness and lustre of metals

• Most metals are hard but sodium, potassium and lithium can be cut using a knife.
• Diamond is the hardest substance.
• Metals such as copper, silver and gold are lustrous (characteristic shine), so used to make statues/jewellery.
• Graphite and iodine are lustrous non-metals.

Malleability, ductility and sonority

• Metals can be beaten into sheets hence are malleable.
• Metals can also be drawn into wires, hence the term ductile
• A metal's response to being struck.
  • When metals tapped they produce a ringing sound.

Metal Conductivity

• Metals are good conductors of electricity except exception of lead.
• Non-metals function as insulators except exception of graphite.
• Metals allow heat to pass through them except aluminium/copper in kitchen utensils.

Density

• Metals usually have high densities (iron=7.8g/cm³, mercury=13.6g/cm³, and gold=19.3g/cm³).
• Metals tend to sink in water.
• Density of water is 1 g/cm³.

Tensile strength and MP/BP

• Metals usually have high tensile strength but sodium, potassium, calcium and zinc do not.
• Metals usually have high melting/boiling points, (gold=1064°C and iron=1538°C).
• A counter example to this is sodium, potassium, lithium and mercury.
• Non-metals low have melting/boiling points, but silicon, graphite and some forms of carbon have very high melting/boiling points.

Corrosion

• Metals like iron and copper react with oxygen and water vapor, forming oxides.
• The process in which metals are gradually eaten away on exposure to air and moisture called corrosion.
• Rusting of iron occurs when iron object is exposed to air and moisture resulting in the formation reddish-brown substance.
• The chemical formula of rust (hydrated ferric oxide) is Fe₂O₃.xH₂O.
• Metals like gold/platinum, being least reactive, do not corrode, and ornaments made of will retain their lustre for a long period.

Protection against Rusting

• Necessary to prevent rusting.
• Preventing contact of the surface layer of iron objects from moisture and air.
• Methods like:
• Painting iron surface w/red lead oxide or oil-based paints.
• Coating machine parts w/oil/grease e.g in automobiles and ships which use slushing oil (wax based product).
• Coating iron surfaces with a layer of zinc galvanisation.

Galvanisation

• The coating of iron objects with a layer of zinc in order to protect it from rusting and corrosion.
• Object that are formed with copper and brass form a greenish layer when contact with air/moisture.
• Tinnning occurs when objects made from these metal utensils/vases are plated in molten tin.
• Process of metal coating on iron objects (tin, chromium, nickel) with the process of electrolysis (electroplating) to give enhanced aesthetic in cutlery, hardware in bathrooms/parts of motor vehicles.

Aluminium

• It is a silvery-white and lustrous metal.
• It is the most abundant metal in earth's crust.

Uses of aluminium

• Foil for packing food/medicines.
• Making electric transmission wires.
• Aluminium powder is mixed with paint prevents rusting.
• Making utensils, containers, cans, window frames and furniture and an important constituent of duralumin/magnalium for aircrafts/ships.

Uses of Iron

• Strong and useful metal which rusts in contact with air and moisture.
• Making construction materials for bridges, buildings and power transmission towers.
• Making cylinder, utensils tools and strong containers (Fig 6.3).
• Railway tracks and ship bodies.
• Making automobile parts and industrial machines.
• decorative items due to its hardness and lustre.

Uses of Zn and Mercury

• Zinc: Brittle metal, blue-grey, resists rusting.
• Is used in galvanisation for coating iron objects, and in electrode of dry cells.
• Mercury: Silvery appearance, and a liquid at room temperature with silvery surface
• Does not stick to glass, expands uniformly on heating, used in clinical thermometers, barometers/laboratory apparatus, to form amalgam (with silver) for dental fillings.

Uses of Gold, Silver

• Gold: Precious, shiny yellow, and stable, so used to make jewelery (Fig. 6.5) and coins, and its shine for years.
• Used in also electronic devices (computers, etc.), makes artificial teeth and dental crowns.
• Silver: Precious withlustrous white colour and its shines disappears over time du oxidization.
• Used on making jewelry, coins and utensils (Fig 6.6.)
• to make dental filings.
• used to electroplate other metals and is an electrode in silver-zinc batteries.

Uses of Metalloids

• Silicon in silicon chips for computers and solar panels for electricity.
• Germanium as a semiconductor for transistors/integrated circuits.
• Arsenic is used to preserve wood.
• Gallium arsenide in making light-emitting diodes (LED).