Distinguish between a pure substance and a mixture based on their composition and properties. Provide two examples for each category from your daily life.

A pure substance consists of only one type of particle (atoms or molecules) and has a fixed, uniform composition and definite properties. For example, water (H₂O) and gold (Au) are pure substances. 

A mixture, on the other hand, contains two or more pure substances physically combined in any proportion. Its composition can vary, and its properties are a combination of the properties of its components. Examples include air (mixture of gases) and lemonade (mixture of water, lemon juice, and sugar).