CLASS 5 · LEARNING KNOWLEDGE

Pure substances and mixtures of substances – basic concepts and distinction

How it works

Pure substances consist of only one type of particle and have defined properties such as melting and boiling point. Mixtures of substances contain at least two different types of particles and often do not show clear melting or boiling points, but ranges. Mixtures of substances can be distinguished into homogeneous (uniformly appearing) and heterogeneous (non-uniformly appearing) mixtures. Examples of pure substances are distilled water or oxygen; examples of mixtures of substances are air or lemonade. The distinction is made by observing the properties and, if necessary, by separation methods.

Note
Pure substances have constant, characteristic properties and consist of only one type of particle; mixtures of substances contain several types of particles and often show non-uniform properties.

An example

Which of the following substances is a pure substance?

Distilled water is a pure substance because it consists only of water molecules and has a fixed boiling point. Lemonade, air and milk are mixtures of substances because they consist of different types of particles.

Try it yourself now

50 Exercises

To the learning unit →

Own explanation and own practice exercises by AmyMath. Subject reference framework: Chemistry. The topic assignment may vary by federal state.