Metalwork - Materials - Mixtures

A Mixture is very different from a Compound. A Mixture is a combination of two or more substances that are not chemically combined. A new substance is not created and the substances of the Mixture keep their properties. There is no fixed limit to the amount of any Element in a mixture. By adding more of one Element or another you can change the physical properties of the substance, but not the chemical properties. You can also destroy the substance or break it up into its parts by means which are not chemical. You should read about Compounds in order to see the difference. We will look at a couple of examples to make this clearer. Take the example of mixing sugar with coffee powder. The coffee and the sugar do not chemically combine. You can still taste the difference. The coffee is brown and sourish, whereas the sugar is sweet and crystalized. And you could seperate the sugar from the coffee grains using a sieve. However when you add hot water to the mixture the sugar dissolves, and a new substance has been formed. The heat of the hot water caused a chemical reaction, therefore a compound has been created and you cannot seperate the coffee and the sugar anymore. Another example would be to mix iron filings with brass filings. The Iron filings are still magnetic and the brass filings are still gold in colour. You could use a magnet to seperate them. But what would happen if you melted the Iron and the Brass, could the magnet remove the Iron ? The answer is no, because the filings have been chemically combined into a solid mass.