An element has previously been defined as a substance composed of only one type of atom. A compound is created when two or more different types of elements combine chemically and a mixture is simply when substances are mixed together but can then be separated by physical means. Let us now take a look at a couple of examples of this.


If we take iron filings, silvery grey small shards of iron and mixing with elemental sulphur which is a yellow powder, we do not make iron sulphide. The reason for this is that the separate elements have not combined chemically, there have been no bonds broken or formed and therefore iron sulphide has not been made. This is an example of a mixture and perhaps one of the easiest ways to separate these two elements would be simply to use a magnet.


Q. What is a mixture?


A. A mixture is an entity made up of two or more separate substances which are not bonded together by chemical means.


The properties of a mixture are just a combination of the properties of the separate substances making up the mixture. For example a mixture of iron (as filings) and sulphur (as powder) will not display the properties of the compound iron sulphide, as the mixture is exactly that -  a mixture -  the iron and the sulphur are not chemically bonded / chemically combined and could easily be separated in this particular case using something as simple as a magnet. Another example could be hydrogen and oxygen, a mixture of hydrogen and oxygen would be a colourless odourless mixture of gases, but when these two gases are combined chemically they produce a wet liquid namely water (I particularly added the word "wet" to show a physical as well as a chemical property, of course another one is the fact that the mixture of gases remain gases, but the compound they form is a liquid)..


Mixtures can be separated in a number of ways, we will come to these in later sections. Mixtures made up of different colours can be separated using a technique called chromatography which you will come across in one of your practical investigations (If you're reading the electronic version of this document you can click on the word chromatography and read more about the practical experiment there).