Materials and recycleing

An element is a simple substance that cannot be split into anything simpler by chemical reactions. Atoms are the smallest particles of an element. Atoms of one element are all the same, and are different from atoms of all the other elements.

All the elements are shown in the periodic table. There are 117 known elements. Each element has a chemical symbol, which is usually one or two letters. A symbol is written with the first letter as a capital, and the second letter lower case, for example:

oxygen – O

carbon – C

iron – Fe 

aluminium – Al

Elements can join together to make compounds. The name of the compound tells you the elements that are in it. Compounds made from two elements always have a name that ends in ‘-ide’.

carbon + oxygen = carbon dioxide

sodium + chlorine = sodium chloride

magnesium + oxygen = magnesium oxide

A chemical formula tells you the name and number of atoms in a compound. The smallest particle of many compounds is called a molecule. Molecules are made up of groups of atoms. Some elements are also made of molecules. For example, a molecule of oxygen contains two oxygen atoms joined together. The formula is O2 . Water contains two atoms of hydrogen and one of oxygen. The formula is H2O.

The properties of a substance describe the way the substance behaves, or measurements that we can make on it. Metals and non-metals have different properties.

Metals

good conductors of heat and electricity

shiny

solids with a high melting point (except for mercury)

Mainly found on the left-hand side and in the centre of the periodic table

three metals are magnetic

flexible

The properties of a substance describe the way the substance behaves, or measurements that we can make on it. Metals and non-metals have different properties.

Non-Metals

poor conductors of heat and electricity

dull

most are solids or gases

found on the right-hand side of the periodic table

no non-metals are magnetic

brittle (break easily instead of bending)

Materials can be classifi ed according to their properties. All the different materials in the world are made up of about 90 different elements. Some useful materials occur naturally, but others have to be manufactured using chemical reactions. In many cases, raw materials are non-renewable. If we can recycle these materials, then we reduce the demand for raw materials. There may also be energy savings as well. A process that uses recycled or renewable materials is sustainable. Waste can also be reduced by re-using objects such as glass bottles or plastic bags.