Ray Oliver takes a look at the histories and properties of some of the elements often left out by schools
The periodic table has more than 100 elements, yet only a few get covered in school science and technology. So to redress the balance, here are a few of the neglected ones which can excite and intrigue students.
Students may wonder what possible connection there can be between horseshoe crabs and the aristocracy. These crabs represent that favourite of natural history programmes, as they are living fossils, virtually unchanged since the Devonian Period.
Their antiquity is not the connection with aristocrats, it is their blue blood. Crab blood is based on haemocyanin, a copper-containing molecule known as a respiratory pigment. The high affinity of haemocyanins for oxygen allows them to perform the same function as haemoglobin in our blood.
Most students will have grown blue crystals of copper sulphate, and this is the basis of Bordeaux mixture, the fungicide used by generations of wine growers. Even copper metal acts as a biocide. There is also evidence that brass door handles (a mixture of copper and zinc) may reduce the spread of contagious infections.
Money from displacement
It is clear from the signs at metal scrap yards that copper is prized more than iron. The industry is now working copper ores as low as 0.5 per cent metal. Ask students to plan how to use cheap scrap iron to displace more valuable copper from solution. Use iron wool or powder to represent scrap iron. Copper sulphate solution is a good source of soluble copper. Leaching with sulphuric acid produces a solution of copper sulphate.
Nickel can be found in the most improbable places. The Earth's core contains nickel, together with iron. Modern analytical techniques have identified nickel in coins dating from 327 BC, about the time of Alexander the Great. The coins, minted during the reign of Euthydemus II, contain about 20 per cent nickel and 78 per cent copper, similar to today's nickel-alloy coins.
Today, the metal is extracted from both sulphide ores and oxide ores called laterites. The major use of nickel is in the manufacture of stainless steel, which consumes about 65 per cent of world production. Although more expensive than mild steel, it has significant advantages. Stainless steel resists corrosion and is used in cookware, domestic appliances and the transport and energy industries.
Nickel hydrides are being developed to store hydrogen fuel for the cars of the future. Since hydrocarbon fuels have environmental drawbacks, research is exploring hydrogen-powered transport where the exhaust gas is just steam. Nickel-cadmium rechargeable batteries already provide us with portable power.
The hydrogen economy
Working in groups, think about the implications of a hydrogen economy as a replacement for fossil fuels. For example:
* source of the hydrogen (water)
* extraction of hydrogen from the source (electrolysis or perhaps a catalytic decomposition using solar energy)
* storage of hydrogen (nickel hydrides or liquefied gas at ultra-low temperatures)
* safety (are you driving a Zeppelin along the motorway?)
* carry out a web search on nickel hydride storage and cryogenic storage.
Lead Lead was extracted from ores in Babylon. The Ancient Greeks mined it near Athens, because many lead ores are rich in silver. The Romans were the first to realise the true potential of lead - in plumbing, from the Latin plumbum. At Pompeii, and the Roman Baths at Bath Spa, original lead waterpipes remain.
The pipe-making technology was rather simple. Melt the lead, pour it over a sloping bed of sand and then roll up the lead sheet into a pipe.
Christopher Wren made extensive use of lead in rebuilding St Paul's Cathedral after the Great Fire of 1666. Limestone blocks were held in place by lead poured molten into channels between the stones. While the limestone blocks have weathered away, the unreactive lead has not, and the difference in height has given us a measure of the rate of decay of the rock. This must be one of the longest running experiments of all time.
Lead sheet absorbs sound very effectively. Put a sheet of lead inside the panels of a wooden door and shut out the sound of music, even heavy metal.
In countries susceptible to earthquakes, lead is incorporated within the foundations. Its ability to dampen vibrations can save a building from collapse.
Grow a lead tree
Few lead salts are soluble. Most lead compounds precipitate from aqueous solutions. Prepare a lead tree like this:
* make a dilute solution of gelatine (it supports the "tree')
* mix with lead nitrate solution before the gel sets
* add a cleaned strip of zinc and wait.
Beautiful crystals of lead grow from the surface of the zinc by a displacement reaction. They resemble the leaves of a tree.
After the revolution of 1848, architect Baron Haussmann rebuilt Paris: all roofs of public buildings were covered in zinc sheet. Its resistance to corrosion meant that the roofs lasted for a century. The metal could then be recycled.
Generations of artists have represented the characteristic blue-grey zinc roofs in their paintings of Paris. Zinc's boiling point is so low for a metal that it can be distilled like alcohol, as described by the Greek polymath Strabo (c63 BC-AD 23). Zinc can thus easily be separated from other metals.
About half of the zinc produced each year is used to coat steel and protect it from corrosion. There are several techniques, the best known being galvanising. When a steel object, such as a car body, is dipped into molten zinc, the surface becomes coated with a zinc-iron alloy. This new surface does not corrode easily and extends the life of the vehicle to 15 years or more.
Zinc-oxide creams control nappy rash and are used as constituents of sun block creams to reduce the dangers to the skin of ultraviolet rays as you slumber on the beach. The Ancient Egyptians are believed to have used zinc oxide in treating eye complaints.
Zinc dust has a very high surface area and oxidises readily. Try adding dust from a spatula to the top of a hot Bunsen flame. Enjoy the green flashes as it burns but avoid breathing in the dust. An alternative is to coat a wooden splint first with a glue stick and then with zinc dust.
Ignite the splint.
A new key stage 45 resource on the history, science and technology of non-ferrous metals is in preparation. The material was previewed at the ASE annual meeting in January. A CD-Rom on aluminium is available from the Aluminium Federation: www.alfed.org.uk
Copper in the curriculum: www.schoolscience.co.uk
International Zinc Association:www.zincworld.org
Lead Development Association International:www.ldaint.orginformation.htm
Nickel Development Institute:www.nidi.org
Ray Oliver teaches at St Albans Girls'