Suspension
In chemistry, a suspension refers to a heterogeneous mixture in which fine particles are dispersed within a liquid or gas but are not dissolved in it. These particles are larger than those in solutions or colloids, leading to some distinct characteristics for suspensions. Here's an overview:
- Particle Size: In a suspension, the dispersed particles typically have a diameter greater than 1000 nanometers. Due to their size, these particles are visible to the naked eye.
- Settling: Unlike solutions, where the solute is completely dissolved, the particles in a suspension can settle over time under the influence of gravity. This is because the particles in a suspension are large enough to be affected by gravity.
- Heterogeneity: Suspensions are heterogeneous mixtures, meaning their composition is not uniform throughout. The particles can often be separated from the dispersion medium (liquid or gas) by filtration or sedimentation.
- Opacity and Tyndall Effect: Suspensions are usually opaque because the large size of the dispersed particles scatters light. They do not exhibit the Tyndall effect (the scattering of light by particles in a colloid), as the particles are too large to scatter light in the same way.
- Examples: Common examples of suspensions include mud in water, flour in water, or dust particles in air. In pharmaceuticals, certain medicines are prepared as suspensions, where the active ingredient is suspended in a liquid.
- Stability and Agitation: Suspensions can be stabilized by agents that increase the viscosity of the medium or by surfactants that reduce particle aggregation. Often, suspensions need to be shaken before use to redistribute the particles evenly throughout the liquid.
- Applications: Suspensions are used in a variety of applications, including in pharmaceuticals, food products, cosmetics, and in industrial processes.
In summary, suspensions are mixtures where particles are dispersed in a fluid but are large enough to settle out over time and can be separated from the dispersion medium. They are commonly encountered in everyday life and have various practical applications.