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basic technology (Secondary School)

Differences and similarities between metals and non-metals

Properties:

Metals: Non-metals:
Strong Brittle
Malleable and ductile Brittle
React with oxygen to form basic oxides React with oxygen to form acidic oxides
Sonorous Dull sound when hit with hammer
High melting and boiling points Low melting and boiling points
Good conductors of electricity Poor conductors of electricity
Good conductors of heat Poor conductors of heat
Mainly solids at room temp. Exception mercury – liquid at room temp. Solids, liquids and gases at room.temp.
Shiny when polished Dull looking
When they form ions, the ions are positive When they form ions, the ions are negative – except hydrogen that forms a positive ion, H+.
High density Low density

 

Common Metals and Non-Metals

Metals: Non-metals:
Calcium Sulphur
Potassium Oxygen
Lead Chlorine
Copper Hydrogen
Aluminium Bromine
Zinc Nitrogen
Lithium Helium

 

Uses of metals and non-metals

Metals

The uses of metals are related to their properties

They are made into jewellery due to their hard and shiny appearance.

They are used to make pans, since they are good conductors of heat.

They are used in electrical cables, because they are malleable, ductile and good conductors of electricity.

They are strong so used to build scaffolding and bridges.

They make a ringing sound, sonorous, hence their use in bell making.

 

Non-metals

Used as insulating material around wire cables since they do not conduct electricity.

Used to make pan handles as they are poor conductors of heat.

alloy of metals;

Alloys are metallic compounds composed of one metal and one or more metal, or non-metal, elements.

Examples of common alloys include:

  • Steel, a combination of iron (metal) and carbon (non-metal)
  • Bronze, a combination of copper (metal) and tin (metal) and
  • Brass, a mixture of copper (metal) and zinc (metal)

Properties

Individual pure metals may possess useful properties, such as good electrical conductivity, high strength, and hardness, or heat and corrosion resistance. Commercial metal alloys attempt to combine these beneficial properties in order to create a metal that is more useful for a particular application than any of its component elements.

 

The development of steel, for example, required finding the right combination of carbon and iron (about 99% iron and 1% carbon, as it turns out) in order to produce a metal that is stronger, lighter and more workable metal than pure iron.

 

The precise properties of new alloys are difficult to calculate because elements do not just combine to become a sum of parts, but form through chemical interactions that depend on their component parts as well as the production method. As a result, much testing is required in the development of new metal alloys.

 

One thing that is for certain is that when metals are alloyed, the melting temperature is always affected. Galinstan®, a low-melt alloy containing gallium, tin, and indium, is liquid at temperatures above 2.2°F (-19°C), meaning that its melting point is 122°F (50°C) lower than pure gallium and more than 212°F (100°C) below indium and tin.

 

Galinstan® and Wood’s Metal are examples of eutectic alloys. Eutectic alloys have the lowest melting point of any alloy combination containing the same elements.

Composition

Thousands of alloy compositions are in regular production, while new compositions are developed regularly. Accepted standard compositions include the purity levels of constituent elements (based on weight content). The makeup, as well as mechanical and physical properties for common alloys, are monitored by international organizations such ISO, SAE International, and ASTM International.

Production

Some metal alloys are naturally occurring and require little processing to be converted into industrial grade materials. Ferro-alloys such as Ferro-chromium and Ferro-silicon, for instance, are produced by smelting mixed ores and are used in the production of various steels.

 

Commercial and trade alloys, however, generally require greater processing and are most often formed by mixing molten metals in a controlled environment. Yet, one would be mistaken in thinking that alloying metals is a simple process.

 

For example, if one were to simply mix molten aluminum with molten lead, we would find that they would separate into layers, much like oil and water. The procedure for combining molten metals, or mixing metals with nonmetals, varies greatly depending on the properties of the elements required.

 

Metal elements have a great variance in their tolerance of heat and gasses. While elements like the refractory metals are stable at high temperatures, others begin to interact with their environment, which can affect purity levels and, ultimately, the alloy quality.

 

Important considerations when alloying metals include the melting temperatures of component metals, impurity levels, the mixing environment and the alloying procedure. In some cases, intermediate alloys must be prepared in order to persuade elements to combine.

 

An alloy of 95.5% aluminum and 4.5% copper is made by first preparing a 50% mixture of the two elements. This mixture has a lower melting point than either pure aluminum or pure copper and acts as a ‘hardener alloy’. This is then introduced to molten aluminum at a rate that creates the right alloy mix.

 

Question:

  1. describe 5 properties of metal
  2. define alloy

 

See also

Wood

Properties of materials

Workshop safety

Work Shop Safety

Safety guidelines

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