5. Models are useful to help explain the difference between elements, compounds and mixtures. Use building blocks to create models to represent the following: • An element containing five atoms • A mixture of three different elements
• A compound made of two different elements
• A compound made of three different elements
Hints: • Each block represents an atom. • An element contains just one type of atom.
• A compound contains two or more types of atoms joined together (chemically combined).
• Mixtures are two or more substances physically combined, e.g. a mixture of elements, a mixture of compounds or a mixture of elements and compounds.
• A mixture of two elements and a compound
• The following substances: water (H2 and carbon dioxide (CO2
) O)
• A mixture of two different compounds • A mixture of an element and a compound
:Fig. 17.5 Separating mixtures
We know that a mixture is formed when two or more substances are physically combined. One of the characteristics of mixtures is that they can often be easily separated. Separation can be done in the laboratory in a number of ways.
Filtration
Filtration is used to separate a solid that does not dissolve in liquid from a liquid. Filtration involves using a material (e.g. filter paper) that allows the liquid but not the solid to pass through. An example of filtration is separating sand (the solid) from water (the liquid) using filter paper.