The Science of Recycling

Further Information

This Further Information section follows on from the programme in introducing the general properties of materials, concentrating on metals. Programme 2 has further information on crude oil, and Programme 3 explores the properties of plastics and fibres.

Metals

Metals are chemical elements. They are usually hard, shiny solids with high melting points.

They may be distinguished from other materials by their high electrical conductivity. (Graphite, an allotrope of carbon, is the only non-metallic element which conducts electricity well.) Metal oxides are basic, and most metals react readily with dilute aqueous acids, producing hydrogen gas.

In the Periodic Table, metals are divided into:

• Group 1: Alkali Metals
• Group 2: Alkaline Earth Metals
• Transition Metals
• Groups 3 and 4, including Aluminium and Lead

Metals can also be arranged as a reactivity series.

Model of a Metal

Aluminium

Iron

Properties of Metals: Comparison with non-metals

Property	Metal	Non-Metal
1. Physical Properties
(a) State at room temperature	Usually solid (occasionally liquid)	Solid, liquid or gas
(b) Melting and boiling points	Usually high	Often low
(c) Electrical conductivity	Conducting when solid	Non-conducting
(d) Strength	Strong and malleable	Often weak and brittle if solid
(e) Density	Usually high	Often low
2. Chemical Properties
(a) Reaction with air	Reactive metals form oxides	May react to form oxides
(b) Nature of oxides	Usually solid. Gives alkaline solution when dissolved in water	Solids, liquids and gases. Gives acidic solution when dissolved in water
(c) Reaction with water	Very reactive metals give hydrogen.	Usually no reaction
(d) Reaction with acids	Reactive metals give hydrogen	Usually no reaction
(e) Type of ions formed	Positively charged	Negatively charged