Properties of metal

A metal is a material (a compound, element or alloy) that is hard when in solid state, opaque, shiny, and which is a good conductor of heat and electricity.

Identification of Metals by Physical Properties

Identification of metals can be defined as a method used to differentiate one particular type of metal from another and from other materials which are non-metals.

Metals can be identified through their properties, which include:

1. Density: This is the weight of a metal and it varies from metal to metal. E.g. aluminum is light and lead is heavy in weight.
2. Colour/Lustre: This is the appearance of a metal when the surface is polished. For example, when polished and examined under a microscope, copper presents a different appearance from polished mild steel.
3. Fusibility: This is the property of a metal which makes it melt and join with other metals while in a liquid form.
4. Magnetic property: This is property that if a metal possesses it, it is attracted by a magnet. It is used to identify ferrous metals from non-ferrous metals.  A magnet will attract ferrous metal while non-ferrous metals will not be attracted by a magnet.
5. Elasticity or Stretching: This is the elastic property of a metal i.e. ability to stretch
6. Brittleness: When a metal breaks suddenly or cracks easily, then it is said to possess brittleness e.g. glass.
7. Conductivity of Heat: When heat spreads from one part of the body of a metal to other parts much more quickly than it does in other metals when heated this is conductivity of heat.
8. Sound Test: This is the sound heard when any metallic materials is hit with a different type of materials. The sound heard differs from metal to metal.
9. Other properties of metals are hardness, malleability and tenacity.

EVALUATION

1. Explain 5 properties of metal.

Classification of Metals

The metals used in engineering can be classified into two categories or classes.

1. Ferrous metals and their alloys

Ferrous metal and their alloys – This is group of metals that contain iron. The metals have no iron. The metals are therefore, not magnetic.  Examples are aluminum, copper, brass etc.  Ferrous metals have the different grades of cast iron and steel.  The different grades of cast iron are grey cast iron, white cast iron and malleable cast iron.  They are used a lot in engineering to make different parts.  Different grade of steel used in engineering construction and machine fabrication are mild steel, medium carbon steel, high speed steel, high tensile steel etc.

An alloy is combination of two or more metal to produce another metal e.g. metal A + metal B = metal C.  Therefore metal C is an alloy of metal A and B e.g. chromium and nickel gives stainless steel.

Non-ferrous metal are no iron based which include these:

(i) Aluminum – This is a non-magnetic metal. When polished, it is silvery-white.  It is very light in weight.  Aluminum has a resistance to corrosion under normal atmospheric conditions.  It is malleable, soft, ductile and a good conductor of heat.

(ii) Copper – it is reddish brown or salmon pink in color. It is malleable and ductile. Copper is a good conductor of heat and electricity.

(iii) Tin – it is bright silvery color. It is used as an alloying element.  Tin is very soft and can hammer and rolled into very thin sheets.  It has a high corrosion resistance.

(iv) Lead – It is very heavy in weight and have grey color

(v) Zinc – It is bluish-white in color. Zinc is brittle and has a good resistance to rust.

Ferrous alloys are those types of metals that are produced when two or more non-ferrous metals are alloyed together. A good example of this is brass. Brass is the mixture of copper, tin and phosphorus. Metal can be found or purchased in different forms. The forms are:

(a) Round section and rectangular.

(b) Tubular and flat section.

(c) Plates and strips.

(d) Wires and channel.

Alloys of Metal

EVALUATION

1. Mention and explain five properties of metal.
2. List four examples of non-ferrous metal.
3. What is an alloy?
4. Mention four forms of metal.