19.1 Pure substances and mixtures . . . . . 209 19.2 Elements and compounds . . . . . . . 210 19.3 Physical changes and chemical reactions 212
Why it matters
The world around us is full of so many different types of materials that we could never list them all. Classifying them into different groups based on their characteristics helps us to understand them.
19.1 Pure substances and mixtures Activity
Divide into groups and decide if the following are solids, liquids or gases at room temperature.
SL Discuss and compare your results with another group.
Classification is a way of organising things into different groups. It helps us to understand them. One way of classifying materials is to divide them into solids, liquids and gases. Another way of classifying materials (matter) is shown in Fig.1.
LO 2, 4 Chemical World strand
Fig. 1 Classifying matter by dividing things into ‘pure substances’ or ‘mixtures’.
All matter is made up of particles and these particles are made from atoms combined in different ways. A pure substance is made of particles that are exactly the same as each other. Water, oxygen and carbon dioxide are all pure substances.
A pure substance is made of particles that are exactly the same as each other.
