Chemical composition largely determines the behaviour of a material in all types of chemical reactions. With metals, the alloying elements and impurities present must be known if the expected performance of the metal is to be predicted with any accuracy. Metals that are found in nature in the forms of oxides, sulphides or carbonates are usually metastable in the metallic form. In the presence of aqueous solutions and atmospheric gases, they tend to revert to one of their more stable forms. This is the process of corrosion. Although polymers and ceramics do not suffer from corrosion as metals do, they too can undergo chemical changes in certain situations. Ultraviolet light, for example, often causes the chemical breakdown of some polymers.

Thermal conductivity: the ability of a material to conduct heat. Generally, metals conduct heat well, and non-metals conduct heat poorly.

Heat Resistance: is determined by the melting point of a material, as well as how stable it is at elevated temperatures. An example is titanium that isn't stronger than an equivalent volume of chrome molybdenum steel at room temperature, but at 500°C has better strength due to its stability at elevated temperatures.

By definition, ferrous metals and alloys are those where iron is the primary constituent, e.g. iron, cast iron, carbon steel and stainless steel. Ferrous metals may be further grouped into either pure iron or steels. Pure iron is rarely used nowadays. Steels may be further grouped according to the amount of carbon added, the most common form of steel are mild steels. These have approximately 0.15% to 0.25% carbon and will also contain some manganese. (Steels are covered in more detail in Chapter 3). It should be noted that most steels used now are low alloy steels with various additions along with carbon to improve their performance

Mild steel is useful as it is easily formed, machined and welded, does not harden much if cooled quickly, and is quite ductile. It finds extensive use in construction. manufacturing, fasteners such as screws and bolts, motor shafts (in non-corrosive environments) and for the housings of any sheet steel objects ranging from toasters to cheaper computer towers.

It should be noted that mild steel, like all steels (except stainless steels), readily corrodes, and that the product of corrosion (commonly known as rust) is porous, thus promoting further corrosion. In most situations the steel must be painted or electroplated or galvanised (coated in zinc) to avoid extensive corrosion. Alternatively another ferrous alloy such as stainless steel could be used.

Stainless Steels: it is appropriate to mention stainless steels because in recent times their use has expanded greatly. Stainless steels are ferrous alloys with at least 10% chromium added; the chromium reacts with oxygen to form a chromium oxide layer that prevents the ferrous alloy from corroding further. The most common stainless covered more deeply in chapter 4. steels in use usually have both chromium and nickel added. Stainless steels are

Copper: this metal is used extensively in the electrical fields due to its high electrical conductivity (second only to silver). It is a heavy metal of red to orange colour, with high ductility and malleability and good corrosion resistance. Copper is used in applications such as electrical wiring, electrical contacts, and the wiring in electric motor armatures and rotors.

Bronze: is not as widely used as brass nowadays but finds extensive use in marine applications. Bronzes are alloys of copper and tin and may have various additions to improve corrosion resistance. They can be used as bearings and springs and also find use as cymbals. With additions of small amounts (greater than 0.1 % but less than 1 %) of phosphorus phosphor bronze is created; this alloy is quite suitable for spring and switch contacts. Bronzes are often used as low maintenance bearings. By pressing and sintering bronze powder a porous sleeve may be produced. The porous article is then impregnated with oil, graphite or polytetrafluroethylene (PTFE or Teflon™) for lubrication, thus producing a simple bearing that requires little maintenance. Lead is often added in amounts up to 5 % to improve the bearing properties.

Aluminium: is a highly used metal which has low density and excellent corrosion resistance; however it has low strength and as such is usually used in alloyed form. Aluminum foil is almost pure aluminum, but industrially aluminium is alloyed with materials like copper, zinc, magnesium, lithium and other metals to gain excellent strength, and due to its low density it usually offers strength to weight ratios better than most ferrous alloys. Unfortunately some aluminum alloys lose aluminium's excellent corrosion resistance when they are alloyed, however this is deemed an acceptable compromise to gain the excellent strength to weight ratio.

There is a wide variety of glasses available. The most used is the soda-lime glass. Glasses are inorganic fusion products that have cooled to rigidity without crystallising (thus they are amorphous).

Of all the ceramics, glass finds the greatest use in modern applications. Glass resists scratching and staining better than most polymers. However it is more expensive, so only better quality household equipment will use glass ahead of a polymer.

Ceramic cooktops also use special glass-ceramic tops which prevent the saucepan from directly contacting the heating element; these can be used as bench space when hotplates are not in use. They are durable, can withstand sudden temperature changes and have moderate impact resistance. These properties are achieved by using a medium alumina/silica glass that is 90% crystalline and virtually pore free. Adding a nucleation agent such as TiO2, and then heat-treating to promote recrystallisation, achieves this. Glass-ceramic has good mechanical strength and toughness, and a very low thermal expansion rate.