1.6 Understand the differences between elements, compounds and mixtures

Elements
Elements consist of one type of atom only. Examples include Aluminium, Copper, Iron, Oxygen and Nitrogen.


Compounds
- A compound is a substance that is made of two or more different elements which are bonded together.
- For example, carbon dioxide is a compound formed from the chemical reaction of carbon and oxygen. One carbon atom reacts with two oxygen atoms to form a molecule of CO2, we know its one carbon and two oxygens because the formula is CO2.
- once formed, it is very difficult to separate molecules (as they have been chemically bonded with each other)
- The properties of a compound are often not the properties of the original elements. For example, hydrogen and oxygen are both gases, but when chemically bonded they form a liquid - H2O (water) - at room temperature.


Mixtures
Mixtures are a group of elements and compounds mixed together. They can be easily separated as they are not bonded together, the parts can be separated out by physical methods such as distillation. An example of a mixture is air, it contains nitrogen, oxygen, carbon dioxide and argon - they are not bonded together, which makes them a mixture not a compound.

The properties of a mixture are just the properties of the separate parts. For example, a mixture of iron and sulfur will show the properties of iron and sulfur, it will also look the same - it will contain grey magnetic bits of iron and bright yellow bits of sulfur.