1. Definition and Composition
Pure substances are materials that consist of only one type of particle. They have a uniform and definite composition. Examples include elements like gold and compounds like water.
Colloidal solutions are mixtures where tiny particles (ranging from 1 nm to 1 µm) are dispersed throughout another substance. These particles are larger than those in a solution but smaller than those in a suspension. An example is milk.
Suspensions are heterogeneous mixtures where larger particles (greater than 1 µm) are suspended in a liquid or gas. These particles can settle over time, such as in muddy water.
2. Stability and Appearance
Pure substances have a consistent appearance and do not change over time. They do not settle or separate into different components.
Colloidal solutions exhibit the Tyndall effect, where light is scattered by the dispersed particles, making them appear cloudy. They remain stable and do not settle out upon standing.
Suspensions will often appear cloudy or murky and can separate into layers if left undisturbed. The larger particles will settle at the bottom, leading to a clear liquid above.
3. Particle Size and Behavior
Pure substances have particles that are uniform in size and shape, leading to predictable physical and chemical properties.
Colloidal solutions have intermediate-sized particles that do not settle but can be affected by temperature and other conditions. They remain mixed due to Brownian motion, which keeps them suspended.
Suspensions contain large particles that can be seen with the naked eye and will eventually settle if left undisturbed. These mixtures require stirring or shaking to maintain uniformity.