A suspension in water is a type of heterogeneous mixture where solid particles are dispersed within the water but are not dissolved.
Based on the provided reference, a suspension is a heterogeneous mixture of a finely distributed solid in a liquid. The solid is not dissolved in the liquid, as is the case with a mixture of salt and water.
Understanding Suspensions
When solid particles are mixed with water but don't dissolve, they form a suspension. Unlike a solution (like salt or sugar dissolved in water), where the solid particles break down to a molecular level and become evenly distributed, the solid particles in a suspension remain as larger, distinct entities.
Key Characteristics
- Heterogeneous: This means the mixture is not uniform throughout. You can often see the different components (the solid particles and the water) with the naked eye or a microscope.
- Solid Particles: These are the undissolved bits.
- Liquid Medium: This is the water in this context.
- Not Dissolved: The key difference from a solution. The solid particles do not break down and chemically bond with the water molecules.
- Particles Settle: Over time, if left undisturbed, the solid particles in a suspension will often settle out at the bottom due to gravity. This is a distinguishing feature from solutions, which remain uniformly mixed indefinitely.
- Turbid or Cloudy: Suspensions are typically opaque or cloudy because the solid particles scatter light passing through them.
Examples of Suspensions in Water
Suspensions are common in everyday life. Here are a few examples:
- Muddy water: Soil or dirt particles mixed with water.
- Sand in water: Coarser particles of sand suspended temporarily.
- Certain medications: Some liquid medicines require shaking before use because they are suspensions (e.g., antacids).
- Orange juice with pulp: Although not strictly a solid-in-liquid suspension in the chemical sense, the pulp particles are suspended in the liquid juice.
- Paint: Pigment particles suspended in a liquid binder.
Suspension vs. Solution vs. Colloid
It's helpful to compare suspensions to other types of mixtures in water:
| Feature | Suspension | Solution | Colloid |
|---|---|---|---|
| Homogeneity | Heterogeneous | Homogeneous | Heterogeneous (appears homogeneous) |
| Particle Size | Large (visible) | Very Small (molecular) | Medium (microscopic) |
| Settling | Settles over time | Does not settle | Does not settle |
| Transparency | Opaque/Cloudy (Turbid) | Transparent | Can be translucent/cloudy (Tyndall effect) |
| Filtration | Particles can be filtered out | Particles pass through | Particles pass through |
Note: The provided reference specifically contrasts suspensions with solutions like salt and water.
Understanding suspensions is important in various fields, from environmental science (sediment transport) to chemistry (reactions involving solid catalysts) and even cooking. The instability of a suspension, causing the solid to settle, is a defining characteristic.
